[RFC PATCH 0/1] Add boot hartid to a Device tree
The RISC-V booting protocol requires the hart id to be present in "a0" register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all possible options, device tree seemed to be the best choice to do this job. The detailed discussion can be found in the following thread.
https://patchwork.ozlabs.org/patch/1233664/
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Atish Patra (1): riscv: Add boot hartid to Device tree
arch/riscv/lib/bootm.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
-- 2.24.0
Linux booting protocol mandates that register "a0" contains the hartid. However, U-boot can not pass the hartid via a0 during EFI boot without breaking the UEFI specification.
Add a DT node under chosen node to indicate the boot hartid. EFI stub in Linux kernel will parse this node and pass it to the real kernel in "a0" before jumping to it.
Signed-off-by: Atish Patra atish.patra@wdc.com --- arch/riscv/lib/bootm.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c index fad16901c5f2..b84cc2db2016 100644 --- a/arch/riscv/lib/bootm.c +++ b/arch/riscv/lib/bootm.c @@ -28,6 +28,19 @@ __weak void board_quiesce_devices(void)
int arch_fixup_fdt(void *blob) { + u32 size; + int chosen_offset, err; + + size = fdt_totalsize(blob); + err = fdt_open_into(blob, blob, size + 32); + if (err < 0) { + printf("Device Tree can't be expanded to accmodate new node"); + return -1; + } + chosen_offset = fdt_path_offset(blob, "/chosen"); + fdt_setprop_u64(blob, chosen_offset, "efi-boot-hartid", + gd->arch.boot_hart); + return 0; }
On Mon, 24 Feb 2020 at 23:20, Atish Patra atish.patra@wdc.com wrote:
Linux booting protocol mandates that register "a0" contains the hartid. However, U-boot can not pass the hartid via a0 during EFI boot without breaking the UEFI specification.
It is not about breaking or violating the UEFI specification. It is about the firmware using a conduit that is already being used to describe the hardware to the OS to pass an extra piece of information that the OS needs.
Add a DT node under chosen node to indicate the boot hartid. EFI stub in Linux kernel will parse this node and pass it to the real kernel in "a0" before jumping to it.
Signed-off-by: Atish Patra atish.patra@wdc.com
arch/riscv/lib/bootm.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/arch/riscv/lib/bootm.c b/arch/riscv/lib/bootm.c index fad16901c5f2..b84cc2db2016 100644 --- a/arch/riscv/lib/bootm.c +++ b/arch/riscv/lib/bootm.c @@ -28,6 +28,19 @@ __weak void board_quiesce_devices(void)
int arch_fixup_fdt(void *blob) {
u32 size;int chosen_offset, err;size = fdt_totalsize(blob);err = fdt_open_into(blob, blob, size + 32);if (err < 0) {printf("Device Tree can't be expanded to accmodate new node");
'accommodate'
return -1;}chosen_offset = fdt_path_offset(blob, "/chosen");fdt_setprop_u64(blob, chosen_offset, "efi-boot-hartid",
I assume that boot hartid does not change value when you boot via UEFI, so this should simply be /chosen/boot-hartid
gd->arch.boot_hart);return 0;}
-- 2.24.0
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in "a0" register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all possible options, device tree seemed to be the best choice to do this job. The detailed discussion can be found in the following thread.
The above mentioned patch is obsoleted by the new suggestion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist? How about EDK2?
I guess boot loaders like GRUB would not have to care about the extra property?
Best regards
Heinrich
Atish Patra (1): riscv: Add boot hartid to Device tree
arch/riscv/lib/bootm.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
-- 2.24.0
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.de wrote:
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in "a0" register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all possible options, device tree seemed to be the best choice to do this job. The detailed discussion can be found in the following thread.
The above mentioned patch is obsoleted by the new suggestion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist? How about EDK2?
RISC-V is not supported at all yet in EDK2.
I guess boot loaders like GRUB would not have to care about the extra property?
Yes, that is basically the point.
On Mon, Feb 24, 2020 at 3:35 PM Ard Biesheuvel ard.biesheuvel@linaro.org wrote:
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.de wrote:
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in "a0" register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all possible options, device tree seemed to be the best choice to do this job. The detailed discussion can be found in the following thread.
The above mentioned patch is obsoleted by the new suggestion.
Thanks for pointing that out to avoid confusion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist?
Yes. But in my local tree ;). It will be included in RISC-V EFI stub support series which I am planning to post in a couple of days.
How about EDK2?
RISC-V is not supported at all yet in EDK2.
The EDK2 patches are out there and reviewed. I guess it will be available in mainline EDK2 pretty soon. Abner agreed that similar patch can be added to EDK2 as well in the previous thread.
I guess boot loaders like GRUB would not have to care about the extra property?
Yes, that is basically the point.
-----Original Message----- From: Atish Patra [mailto:atishp@atishpatra.org] Sent: Tuesday, February 25, 2020 7:52 AM To: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Heinrich Schuchardt xypron.glpk@gmx.de; Atish Patra atish.patra@wdc.com; U-Boot Mailing List u-boot@lists.denx.de; Alexander Graf agraf@csgraf.de; Anup Patel anup.patel@wdc.com; Bin Meng bmeng.cn@gmail.com; Joe Hershberger joe.hershberger@ni.com; Loic Pallardy loic.pallardy@st.com; Lukas Auer lukas.auer@aisec.fraunhofer.de; Marek Behún marek.behun@nic.cz; Marek Vasut marek.vasut@gmail.com; Patrick Delaunay patrick.delaunay@st.com; Peng Fan peng.fan@nxp.com; Philippe Reynes philippe.reynes@softathome.com; Simon Glass sjg@chromium.org; Simon Goldschmidt simon.k.r.goldschmidt@gmail.com; Stefano Babic sbabic@denx.de; Thierry Reding treding@nvidia.com; Tom Rini trini@konsulko.com; leif@nuviainc.com; Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com; Schaefer, Daniel (DualStudy) daniel.schaefer@hpe.com Subject: Re: [RFC PATCH 0/1] Add boot hartid to a Device tree
On Mon, Feb 24, 2020 at 3:35 PM Ard Biesheuvel ard.biesheuvel@linaro.org wrote:
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.de
wrote:
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in "a0" register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all
possible options, device tree seemed to be the best choice to do this job.
The detailed discussion can be found in the following thread.
INVALID URI REMOVED
abs.org_patch_1233664_&d=DwIBaQ&c=C5b8zRQO1miGmBeVZ2LFWg&r=_S N6FZB
N4Vgi4Ulkskz6qU3NYRO03nHp9P7Z5q59A3E&m=J8GY_HS3fV_cJH9duXP739y 0hDK
3qfHGNx2Dpcf-UBY&s=iVpRlpTOME_A-
O5STNbXXawkW24gxy2yi56Q8AtZ2bI&e=
The above mentioned patch is obsoleted by the new suggestion.
Thanks for pointing that out to avoid confusion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using
bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist?
Yes. But in my local tree ;). It will be included in RISC-V EFI stub support series which I am planning to post in a couple of days.
How about EDK2?
RISC-V is not supported at all yet in EDK2.
The EDK2 patches are out there and reviewed. I guess it will be available in mainline EDK2 pretty soon.
Yes, currently we are working on edk2 CI testing for RISCV64 arch. We hope edk2 RISC-V port could be in mainstream in Mar.
Abner agreed that similar patch can be added to EDK2 as well in the previous thread.
Yes, this will be another TODO for edk2 to add similar DT changes if we want to boot system from edk2 firmware to EFI Stub and Linux kernel. We do not have that so far.
I guess boot loaders like GRUB would not have to care about the extra property?
Yes, that is basically the point.
-- Regards, Atish
On Tue, 25 Feb 2020 at 09:28, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com wrote:
-----Original Message----- From: Atish Patra [mailto:atishp@atishpatra.org]
<snip header soup>
On Mon, Feb 24, 2020 at 3:35 PM Ard Biesheuvel ard.biesheuvel@linaro.org wrote:
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.de
wrote:
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in "a0" register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all
possible options, device tree seemed to be the best choice to do this job.
The detailed discussion can be found in the following thread.
INVALID URI REMOVED
abs.org_patch_1233664_&d=DwIBaQ&c=C5b8zRQO1miGmBeVZ2LFWg&r=_S N6FZB
N4Vgi4Ulkskz6qU3NYRO03nHp9P7Z5q59A3E&m=J8GY_HS3fV_cJH9duXP739y 0hDK
3qfHGNx2Dpcf-UBY&s=iVpRlpTOME_A-
O5STNbXXawkW24gxy2yi56Q8AtZ2bI&e=
The above mentioned patch is obsoleted by the new suggestion.
Thanks for pointing that out to avoid confusion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using
bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist?
Yes. But in my local tree ;). It will be included in RISC-V EFI stub support series which I am planning to post in a couple of days.
How about EDK2?
RISC-V is not supported at all yet in EDK2.
The EDK2 patches are out there and reviewed. I guess it will be available in mainline EDK2 pretty soon.
Yes, currently we are working on edk2 CI testing for RISCV64 arch. We hope edk2 RISC-V port could be in mainstream in Mar.
Excellent! Is this core support? Or do you have a platform implemented as well that can be upstreamed?
Abner agreed that similar patch can be added to EDK2 as well in the previous thread.
Yes, this will be another TODO for edk2 to add similar DT changes if we want to boot system from edk2 firmware to EFI Stub and Linux kernel. We do not have that so far.
I guess boot loaders like GRUB would not have to care about the extra property?
Yes, that is basically the point.
-- Regards, Atish
-----Original Message----- From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] Sent: Tuesday, February 25, 2020 4:48 PM To: Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com Cc: Atish Patra atishp@atishpatra.org; Heinrich Schuchardt xypron.glpk@gmx.de; Atish Patra atish.patra@wdc.com; U-Boot Mailing List u-boot@lists.denx.de; Alexander Graf agraf@csgraf.de; Anup Patel anup.patel@wdc.com; Bin Meng bmeng.cn@gmail.com; Joe Hershberger joe.hershberger@ni.com; Loic Pallardy loic.pallardy@st.com; Lukas Auer lukas.auer@aisec.fraunhofer.de; Marek Behún marek.behun@nic.cz; Marek Vasut marek.vasut@gmail.com; Patrick Delaunay patrick.delaunay@st.com; Peng Fan peng.fan@nxp.com; Philippe Reynes philippe.reynes@softathome.com; Simon Glass sjg@chromium.org; Simon Goldschmidt simon.k.r.goldschmidt@gmail.com; Stefano Babic sbabic@denx.de; Thierry Reding treding@nvidia.com; Tom Rini trini@konsulko.com; leif@nuviainc.com; Schaefer, Daniel (DualStudy) daniel.schaefer@hpe.com Subject: Re: [RFC PATCH 0/1] Add boot hartid to a Device tree
On Tue, 25 Feb 2020 at 09:28, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com wrote:
-----Original Message----- From: Atish Patra [mailto:atishp@atishpatra.org]
<snip header soup>
On Mon, Feb 24, 2020 at 3:35 PM Ard Biesheuvel ard.biesheuvel@linaro.org wrote:
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.de
wrote:
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in
"a0"
register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all
possible options, device tree seemed to be the best choice to do this job.
The detailed discussion can be found in the following thread.
INVALID URI REMOVED
abs.org_patch_1233664_&d=DwIBaQ&c=C5b8zRQO1miGmBeVZ2LFWg&r=_S
N6FZB
N4Vgi4Ulkskz6qU3NYRO03nHp9P7Z5q59A3E&m=J8GY_HS3fV_cJH9duXP739y
0hDK
3qfHGNx2Dpcf-UBY&s=iVpRlpTOME_A-
O5STNbXXawkW24gxy2yi56Q8AtZ2bI&e=
The above mentioned patch is obsoleted by the new suggestion.
Thanks for pointing that out to avoid confusion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using
bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist?
Yes. But in my local tree ;). It will be included in RISC-V EFI stub support series which I am planning to post in a couple of days.
How about EDK2?
RISC-V is not supported at all yet in EDK2.
The EDK2 patches are out there and reviewed. I guess it will be available in mainline EDK2 pretty soon.
Yes, currently we are working on edk2 CI testing for RISCV64 arch. We
hope edk2 RISC-V port could be in mainstream in Mar.
Excellent! Is this core support? Or do you have a platform implemented as well that can be upstreamed?
Yes we do have platform implementations to be upstreamed, below is the latest status of RISC-V edk2 port. We will have to update status later because we just merged OpenSBI tag 0.6 to edk2 RISC-V. https://github.com/riscv/riscv-uefi-edk2-docs
Abner agreed that similar patch can be added to EDK2 as well in the previous thread.
Yes, this will be another TODO for edk2 to add similar DT changes if we
want to boot system from edk2 firmware to EFI Stub and Linux kernel. We do not have that so far.
I guess boot loaders like GRUB would not have to care about the extra property?
Yes, that is basically the point.
-- Regards, Atish
On Tue, 25 Feb 2020 at 09:59, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com wrote:
-----Original Message----- From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] Sent: Tuesday, February 25, 2020 4:48 PM To: Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com Cc: Atish Patra atishp@atishpatra.org; Heinrich Schuchardt xypron.glpk@gmx.de; Atish Patra atish.patra@wdc.com; U-Boot Mailing List u-boot@lists.denx.de; Alexander Graf agraf@csgraf.de; Anup Patel anup.patel@wdc.com; Bin Meng bmeng.cn@gmail.com; Joe Hershberger joe.hershberger@ni.com; Loic Pallardy loic.pallardy@st.com; Lukas Auer lukas.auer@aisec.fraunhofer.de; Marek Behún marek.behun@nic.cz; Marek Vasut marek.vasut@gmail.com; Patrick Delaunay patrick.delaunay@st.com; Peng Fan peng.fan@nxp.com; Philippe Reynes philippe.reynes@softathome.com; Simon Glass sjg@chromium.org; Simon Goldschmidt simon.k.r.goldschmidt@gmail.com; Stefano Babic sbabic@denx.de; Thierry Reding treding@nvidia.com; Tom Rini trini@konsulko.com; leif@nuviainc.com; Schaefer, Daniel (DualStudy) daniel.schaefer@hpe.com Subject: Re: [RFC PATCH 0/1] Add boot hartid to a Device tree
On Tue, 25 Feb 2020 at 09:28, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com wrote:
-----Original Message----- From: Atish Patra [mailto:atishp@atishpatra.org]
<snip header soup>
On Mon, Feb 24, 2020 at 3:35 PM Ard Biesheuvel ard.biesheuvel@linaro.org wrote:
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.de
wrote:
On 2/24/20 11:19 PM, Atish Patra wrote: > The RISC-V booting protocol requires the hart id to be present in
"a0"
> register. This is not a problem for bootm/booti commands as > they directly jump to Linux kernel. However, bootefi jumps to > a EFI boot stub code in Linux kernel which acts a loader and > jumps to real Linux after terminating the boot services. This > boot stub code has to be aware of the boot hart id so that it > can set it in "a0" before jumping to Linux kernel. Currently, > UEFI protocol doesn't have any mechanism to pass the boot hart > id to an EFI executable. We should keep it this way as this is > a RISC-V specific requirement rather than a UEFI requirement. > Out of the all
possible options, device tree seemed to be the best choice to do this job.
> The detailed discussion can be found in the following thread. > > INVALID URI REMOVED >
abs.org_patch_1233664_&d=DwIBaQ&c=C5b8zRQO1miGmBeVZ2LFWg&r=_S
N6FZB
>
N4Vgi4Ulkskz6qU3NYRO03nHp9P7Z5q59A3E&m=J8GY_HS3fV_cJH9duXP739y
0hDK
> 3qfHGNx2Dpcf-UBY&s=iVpRlpTOME_A-
O5STNbXXawkW24gxy2yi56Q8AtZ2bI&e=
The above mentioned patch is obsoleted by the new suggestion.
Thanks for pointing that out to avoid confusion.
> > This patch updates the device tree in arch_fixup_fdt() which > is common for all booting commands. As a result, the DT > modification doesn't require any efi related arch specific > functions and all DT related modifications are contained at > one place. However, the hart id node will be available for > Linux even if the kernel is booted using
bootm command.
> > If that is not acceptable, we can always move the code to an > efi specific function.
Does a related Linux patch already exist?
Yes. But in my local tree ;). It will be included in RISC-V EFI stub support series which I am planning to post in a couple of days.
How about EDK2?
RISC-V is not supported at all yet in EDK2.
The EDK2 patches are out there and reviewed. I guess it will be available in mainline EDK2 pretty soon.
Yes, currently we are working on edk2 CI testing for RISCV64 arch. We
hope edk2 RISC-V port could be in mainstream in Mar.
Excellent! Is this core support? Or do you have a platform implemented as well that can be upstreamed?
Yes we do have platform implementations to be upstreamed, below is the latest status of RISC-V edk2 port. We will have to update status later because we just merged OpenSBI tag 0.6 to edk2 RISC-V. https://github.com/riscv/riscv-uefi-edk2-docs
Good to know! I saw some patches going by on the mailing list, but it is hard to derive the current state of affairs from that.
I'm glad to see you did not make the same mistake we made on ARM and omit the PEI phase entirely.
What I did notice is the use of APRIORI PEI and APRIORI DXE sections in your platform descriptions. I recommend you try to avoid that, as it is a maintenance burden going forward: instead, please use dummy protocols and NULL library class resolutions if you need to make generic components depend on platform specific protocols. Also, please document this - the APRIORI section does not explain *why* you have to circumvent the ordinary dependency tree based module dispatch.
Hi,
I have started to implement the corresponding changes in EDK2: https://github.com/changab/edk2-staging-riscv/compare/5f63e9249751ccb9302514... What happens is: The DTB is embedded in the FW image and passed to sbi_init in SEC phase. We initialize OpenSBI as early as possible and because it also wants to modify the device tree, I have to pass it the DTB as next_arg1. Then it's passed to PEI in the firmware context and further to DXE via a HOB. In DXE the boot-hartid is inserted and it's installed into the EFI system config table from where the EFISTUB reads it.
Unfortunately I don't get any console output after the EFISTUB calls ExitBootServices, so my patch is still WIP. Atish, which platform file in OpenSBI did you use to test your changes? platform/qemu/virt/platform.c or platform/sifive/fu540/platform.c ? Maybe the failure is unrelated to the new patches - we've never booted Linux from EDKII yet.
I'm a bit skeptical whether DT is the best way to pass the boothartid to the kernel. Ard has argued that it's good because it's independent from UEFI, but the proper kernel doesn't read the hartid from there - it gets it from a0. Only the EFISTUB reads the hartid from the device tree. Therefore the solution we need is EFI specific anyways, right? One of the design goals is that we don't want to force bootloaders, which load the EFISTUB (e.g. UEFI Shell, grub chainloading, systemd-boot), to change.
If we let the firmware embed the hartid in the DT, the user cannot swap out the DT later for their custom one. They need to use the one given by the firmware. Of course we could add commands and config to bootloaders to load and fixup (embed hartid) the device tree... but, as mentioned earlier, we want to avoid that. Additionally from EDKII side we're also planning to run later stages, including the bootloader, in S-Mode, where they wouldn't even have access to mhartid and thus couldn't fixup the DT.
If instead the firmware writes the hartid into the EFI system config table, the EFISTUB can read it from there, just like it does the device tree already. Then bootloaders can put a user supplied DT in the config table, too, like they always have.
What do you all think - does that make sense?
- Daniel On 2/25/20 10:07 AM, Ard Biesheuvel wrote:
On Tue, 25 Feb 2020 at 09:59, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.commailto:abner.chang@hpe.com wrote:
-----Original Message----- From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] Sent: Tuesday, February 25, 2020 4:48 PM To: Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.commailto:abner.chang@hpe.com Cc: Atish Patra atishp@atishpatra.orgmailto:atishp@atishpatra.org; Heinrich Schuchardt xypron.glpk@gmx.demailto:xypron.glpk@gmx.de; Atish Patra atish.patra@wdc.commailto:atish.patra@wdc.com; U-Boot Mailing List u-boot@lists.denx.demailto:u-boot@lists.denx.de; Alexander Graf agraf@csgraf.demailto:agraf@csgraf.de; Anup Patel anup.patel@wdc.commailto:anup.patel@wdc.com; Bin Meng bmeng.cn@gmail.commailto:bmeng.cn@gmail.com; Joe Hershberger joe.hershberger@ni.commailto:joe.hershberger@ni.com; Loic Pallardy loic.pallardy@st.commailto:loic.pallardy@st.com; Lukas Auer lukas.auer@aisec.fraunhofer.demailto:lukas.auer@aisec.fraunhofer.de; Marek Behún marek.behun@nic.czmailto:marek.behun@nic.cz; Marek Vasut marek.vasut@gmail.commailto:marek.vasut@gmail.com; Patrick Delaunay patrick.delaunay@st.commailto:patrick.delaunay@st.com; Peng Fan peng.fan@nxp.commailto:peng.fan@nxp.com; Philippe Reynes philippe.reynes@softathome.commailto:philippe.reynes@softathome.com; Simon Glass sjg@chromium.orgmailto:sjg@chromium.org; Simon Goldschmidt simon.k.r.goldschmidt@gmail.commailto:simon.k.r.goldschmidt@gmail.com; Stefano Babic sbabic@denx.demailto:sbabic@denx.de; Thierry Reding treding@nvidia.commailto:treding@nvidia.com; Tom Rini trini@konsulko.commailto:trini@konsulko.com; leif@nuviainc.commailto:leif@nuviainc.com; Schaefer, Daniel (DualStudy) daniel.schaefer@hpe.commailto:daniel.schaefer@hpe.com Subject: Re: [RFC PATCH 0/1] Add boot hartid to a Device tree
On Tue, 25 Feb 2020 at 09:28, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.commailto:abner.chang@hpe.com wrote:
-----Original Message----- From: Atish Patra [mailto:atishp@atishpatra.org]
<snip header soup>
On Mon, Feb 24, 2020 at 3:35 PM Ard Biesheuvel ard.biesheuvel@linaro.orgmailto:ard.biesheuvel@linaro.org wrote:
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.demailto:xypron.glpk@gmx.de
wrote:
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in
"a0"
register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all
possible options, device tree seemed to be the best choice to do this job.
The detailed discussion can be found in the following thread.
INVALID URI REMOVED
abs.org_patch_1233664_&d=DwIBaQ&c=C5b8zRQO1miGmBeVZ2LFWg&r=_S
N6FZB
N4Vgi4Ulkskz6qU3NYRO03nHp9P7Z5q59A3E&m=J8GY_HS3fV_cJH9duXP739y
0hDK
3qfHGNx2Dpcf-UBY&s=iVpRlpTOME_A-
O5STNbXXawkW24gxy2yi56Q8AtZ2bI&e=
The above mentioned patch is obsoleted by the new suggestion.
Thanks for pointing that out to avoid confusion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using
bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist?
Yes. But in my local tree ;). It will be included in RISC-V EFI stub support series which I am planning to post in a couple of days.
How about EDK2?
RISC-V is not supported at all yet in EDK2.
The EDK2 patches are out there and reviewed. I guess it will be available in mainline EDK2 pretty soon.
Yes, currently we are working on edk2 CI testing for RISCV64 arch. We
hope edk2 RISC-V port could be in mainstream in Mar.
Excellent! Is this core support? Or do you have a platform implemented as well that can be upstreamed?
Yes we do have platform implementations to be upstreamed, below is the latest status of RISC-V edk2 port. We will have to update status later because we just merged OpenSBI tag 0.6 to edk2 RISC-V. https://github.com/riscv/riscv-uefi-edk2-docs
Good to know! I saw some patches going by on the mailing list, but it is hard to derive the current state of affairs from that.
I'm glad to see you did not make the same mistake we made on ARM and omit the PEI phase entirely.
What I did notice is the use of APRIORI PEI and APRIORI DXE sections in your platform descriptions. I recommend you try to avoid that, as it is a maintenance burden going forward: instead, please use dummy protocols and NULL library class resolutions if you need to make generic components depend on platform specific protocols. Also, please document this - the APRIORI section does not explain *why* you have to circumvent the ordinary dependency tree based module dispatch.
On Thu, 5 Mar 2020 at 04:28, Schaefer, Daniel (DualStudy) daniel.schaefer@hpe.com wrote:
Hi,
I have started to implement the corresponding changes in EDK2: https://github.com/changab/edk2-staging-riscv/compare/5f63e9249751ccb9302514... What happens is: The DTB is embedded in the FW image and passed to sbi_init in SEC phase. We initialize OpenSBI as early as possible and because it also wants to modify the device tree, I have to pass it the DTB as next_arg1. Then it's passed to PEI in the firmware context and further to DXE via a HOB. In DXE the boot-hartid is inserted and it's installed into the EFI system config table from where the EFISTUB reads it.
Unfortunately I don't get any console output after the EFISTUB calls ExitBootServices, so my patch is still WIP. Atish, which platform file in OpenSBI did you use to test your changes? platform/qemu/virt/platform.c or platform/sifive/fu540/platform.c ? Maybe the failure is unrelated to the new patches - we've never booted Linux from EDKII yet.
I'm a bit skeptical whether DT is the best way to pass the boothartid to the kernel. Ard has argued that it's good because it's independent from UEFI, but the proper kernel doesn't read the hartid from there - it gets it from a0. Only the EFISTUB reads the hartid from the device tree. Therefore the solution we need is EFI specific anyways, right? One of the design goals is that we don't want to force bootloaders, which load the EFISTUB (e.g. UEFI Shell, grub chainloading, systemd-boot), to change.
If we let the firmware embed the hartid in the DT, the user cannot swap out the DT later for their custom one. They need to use the one given by the firmware. Of course we could add commands and config to bootloaders to load and fixup (embed hartid) the device tree... but, as mentioned earlier, we want to avoid that. Additionally from EDKII side we're also planning to run later stages, including the bootloader, in S-Mode, where they wouldn't even have access to mhartid and thus couldn't fixup the DT.
If instead the firmware writes the hartid into the EFI system config table, the EFISTUB can read it from there, just like it does the device tree already. Then bootloaders can put a user supplied DT in the config table, too, like they always have.
What do you all think - does that make sense?
It doesn't really matter from the EFI stub pov if the information comes from the DT or from another config table. But the idea that RISC-V is 'special', and that you have to pass *two* pieces of information around instead of just one like on every other platform is something that you should really think about carefully - there may be other places where it will bite you down the road.
Also, the idea that a DT is a file that you ship with the kernel is giving a *lot* of grief in the ARM world. The DT describes the hardware, not the software, and so it is the responsibility of the platform to provide it. If the platform gives you some way to drop in another version of the DT in one way or the other, that is absolutely fine, but in this case, the platform should know how to update /chosen/boot-hartid (which it already can, in any case). But don't make it part of the boot protocol, it really doesn't belong there.
On Wed, Mar 4, 2020 at 7:22 PM Schaefer, Daniel (DualStudy) daniel.schaefer@hpe.com wrote:
Hi,
I have started to implement the corresponding changes in EDK2: https://github.com/changab/edk2-staging-riscv/compare/5f63e9249751ccb9302514... What happens is: The DTB is embedded in the FW image and passed to sbi_init in SEC phase. We initialize OpenSBI as early as possible and because it also wants to modify the device tree, I have to pass it the DTB as next_arg1. Then it's passed to PEI in the firmware context and further to DXE via a HOB. In DXE the boot-hartid is inserted and it's installed into the EFI system config table from where the EFISTUB reads it.
Unfortunately I don't get any console output after the EFISTUB calls ExitBootServices, so my patch is still WIP. Atish, which platform file in OpenSBI did you use to test your changes? platform/qemu/virt/platform.c or platform/sifive/fu540/platform.c ?
Both. I have verified bootefi boot on Qemu and Unleashed.
Maybe the failure is unrelated to the new patches - we've never booted Linux from EDKII yet.
I have never tried EDKII patches as well. I will give it a try. You can add a quick hack can be added in OpenSBI to add the chosen node easily. By doing that, you ensure that EDK2 is unchanged and try my EFI stub patches. I might have missed something in EFI stub as well :).
I'm a bit skeptical whether DT is the best way to pass the boothartid to the kernel. Ard has argued that it's good because it's independent from UEFI, but the proper kernel doesn't read the hartid from there - it gets it from a0. Only the EFISTUB reads the hartid from the device tree. Therefore the solution we need is EFI specific anyways, right?
yes.
One of the design goals is that we don't want to force bootloaders, which load the EFISTUB (e.g. UEFI Shell, grub chainloading, systemd-boot), to change.
I don't know how systemd-boot works but grub doesn't need to modify DT. The stage loading the grub must have already made that modification.
If we let the firmware embed the hartid in the DT, the user cannot swap out the DT later for their custom one. They need to use the one given by the firmware. Of course we could add commands and config to bootloaders to load and fixup (embed hartid) the device tree... but, as mentioned earlier, we want to avoid that. Additionally from EDKII side we're also planning to run later stages, including the bootloader, in S-Mode, where they wouldn't even have access to mhartid and thus couldn't fixup the DT.
If instead the firmware writes the hartid into the EFI system config table, the EFISTUB can read it from there, just like it does the device tree already. Then bootloaders can put a user supplied DT in the config table, too, like they always have.
What do you all think - does that make sense?
- Daniel
On 2/25/20 10:07 AM, Ard Biesheuvel wrote:
On Tue, 25 Feb 2020 at 09:59, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com wrote:
-----Original Message----- From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] Sent: Tuesday, February 25, 2020 4:48 PM To: Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com Cc: Atish Patra atishp@atishpatra.org; Heinrich Schuchardt xypron.glpk@gmx.de; Atish Patra atish.patra@wdc.com; U-Boot Mailing List u-boot@lists.denx.de; Alexander Graf agraf@csgraf.de; Anup Patel anup.patel@wdc.com; Bin Meng bmeng.cn@gmail.com; Joe Hershberger joe.hershberger@ni.com; Loic Pallardy loic.pallardy@st.com; Lukas Auer lukas.auer@aisec.fraunhofer.de; Marek Behún marek.behun@nic.cz; Marek Vasut marek.vasut@gmail.com; Patrick Delaunay patrick.delaunay@st.com; Peng Fan peng.fan@nxp.com; Philippe Reynes philippe.reynes@softathome.com; Simon Glass sjg@chromium.org; Simon Goldschmidt simon.k.r.goldschmidt@gmail.com; Stefano Babic sbabic@denx.de; Thierry Reding treding@nvidia.com; Tom Rini trini@konsulko.com; leif@nuviainc.com; Schaefer, Daniel (DualStudy) daniel.schaefer@hpe.com Subject: Re: [RFC PATCH 0/1] Add boot hartid to a Device tree
On Tue, 25 Feb 2020 at 09:28, Chang, Abner (HPS SW/FW Technologist) abner.chang@hpe.com wrote:
-----Original Message----- From: Atish Patra [mailto:atishp@atishpatra.org]
<snip header soup>
On Mon, Feb 24, 2020 at 3:35 PM Ard Biesheuvel ard.biesheuvel@linaro.org wrote:
On Tue, 25 Feb 2020 at 00:22, Heinrich Schuchardt xypron.glpk@gmx.de
wrote:
On 2/24/20 11:19 PM, Atish Patra wrote:
The RISC-V booting protocol requires the hart id to be present in
"a0"
register. This is not a problem for bootm/booti commands as they directly jump to Linux kernel. However, bootefi jumps to a EFI boot stub code in Linux kernel which acts a loader and jumps to real Linux after terminating the boot services. This boot stub code has to be aware of the boot hart id so that it can set it in "a0" before jumping to Linux kernel. Currently, UEFI protocol doesn't have any mechanism to pass the boot hart id to an EFI executable. We should keep it this way as this is a RISC-V specific requirement rather than a UEFI requirement. Out of the all
possible options, device tree seemed to be the best choice to do this job.
The detailed discussion can be found in the following thread.
INVALID URI REMOVED
abs.org_patch_1233664_&d=DwIBaQ&c=C5b8zRQO1miGmBeVZ2LFWg&r=_S
N6FZB
N4Vgi4Ulkskz6qU3NYRO03nHp9P7Z5q59A3E&m=J8GY_HS3fV_cJH9duXP739y
0hDK
3qfHGNx2Dpcf-UBY&s=iVpRlpTOME_A-
O5STNbXXawkW24gxy2yi56Q8AtZ2bI&e=
The above mentioned patch is obsoleted by the new suggestion.
Thanks for pointing that out to avoid confusion.
This patch updates the device tree in arch_fixup_fdt() which is common for all booting commands. As a result, the DT modification doesn't require any efi related arch specific functions and all DT related modifications are contained at one place. However, the hart id node will be available for Linux even if the kernel is booted using
bootm command.
If that is not acceptable, we can always move the code to an efi specific function.
Does a related Linux patch already exist?
Yes. But in my local tree ;). It will be included in RISC-V EFI stub support series which I am planning to post in a couple of days.
How about EDK2?
RISC-V is not supported at all yet in EDK2.
The EDK2 patches are out there and reviewed. I guess it will be available in mainline EDK2 pretty soon.
Yes, currently we are working on edk2 CI testing for RISCV64 arch. We
hope edk2 RISC-V port could be in mainstream in Mar.
Excellent! Is this core support? Or do you have a platform implemented as well that can be upstreamed?
Yes we do have platform implementations to be upstreamed, below is the latest status of RISC-V edk2 port. We will have to update status later because we just merged OpenSBI tag 0.6 to edk2 RISC-V. https://github.com/riscv/riscv-uefi-edk2-docs
Good to know! I saw some patches going by on the mailing list, but it is hard to derive the current state of affairs from that.
I'm glad to see you did not make the same mistake we made on ARM and omit the PEI phase entirely.
What I did notice is the use of APRIORI PEI and APRIORI DXE sections in your platform descriptions. I recommend you try to avoid that, as it is a maintenance burden going forward: instead, please use dummy protocols and NULL library class resolutions if you need to make generic components depend on platform specific protocols. Also, please document this - the APRIORI section does not explain *why* you have to circumvent the ordinary dependency tree based module dispatch.
participants (6)
-
Ard Biesheuvel -
Atish Patra -
Atish Patra -
Chang, Abner (HPS SW/FW Technologist) -
Heinrich Schuchardt -
Schaefer, Daniel (DualStudy)