[U-Boot] [PATCH v2 2/3] x86: fsp: Load GDT before calling FspInitEntry
Currently the FSP execution environment GDT is setup by U-Boot in arch/x86/cpu/start16.S, which works pretty well. But if we try to move the FspInitEntry call a little bit later to better fit into U-Boot's initialization sequence, FSP will fail to bring up the AP due to #GP fault as AP's GDT is duplicated from BSP whose GDT is now moved into CAR, and unfortunately FSP calls AP initialization after it disables the CAR. So basically the BSP's GDT still refers to the one in the CAR, whose content is no longer available, so when AP starts up and loads its segment register, it blows up.
To resolve this, we load GDT before calling into FspInitEntry. The GDT is the same one used in arch/x86/cpu/start16.S, which is in the ROM and exists forever.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
---
Changes in v2: - Use CONFIG_RESET_SEG_START to avoid duplication
arch/x86/cpu/cpu.c | 20 ++++++++++++++++++++ arch/x86/cpu/start16.S | 1 + arch/x86/include/asm/u-boot-x86.h | 3 +++ arch/x86/lib/fsp/fsp_support.c | 3 +++ 4 files changed, 27 insertions(+)
diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c index bb4a110..f4ebc97 100644 --- a/arch/x86/cpu/cpu.c +++ b/arch/x86/cpu/cpu.c @@ -164,6 +164,26 @@ void setup_gdt(gd_t *id, u64 *gdt_addr) load_fs(X86_GDT_ENTRY_32BIT_FS); }
+#ifdef CONFIG_HAVE_FSP +/* + * Setup FSP execution environment GDT + * + * Per Intel FSP external architecture specification, before calling any FSP + * APIs, we need make sure the system is in flat 32-bit mode and both the code + * and data selectors should have full 4GB access range. Here we reuse the one + * we used in arch/x86/cpu/start16.S, and reload the segement registers. + */ +void setup_fsp_gdt(void) +{ + load_gdt((const u64 *)((u32)&gdt + CONFIG_RESET_SEG_START), 4); + load_ds(X86_GDT_ENTRY_32BIT_DS); + load_ss(X86_GDT_ENTRY_32BIT_DS); + load_es(X86_GDT_ENTRY_32BIT_DS); + load_fs(X86_GDT_ENTRY_32BIT_DS); + load_gs(X86_GDT_ENTRY_32BIT_DS); +} +#endif + int __weak x86_cleanup_before_linux(void) { #ifdef CONFIG_BOOTSTAGE_STASH diff --git a/arch/x86/cpu/start16.S b/arch/x86/cpu/start16.S index 826e2b4..a3e7ab4 100644 --- a/arch/x86/cpu/start16.S +++ b/arch/x86/cpu/start16.S @@ -75,6 +75,7 @@ gdt_ptr:
/* Some CPUs are picky about GDT alignment... */ .align 16 +.globl gdt gdt: /* * The GDT table ... diff --git a/arch/x86/include/asm/u-boot-x86.h b/arch/x86/include/asm/u-boot-x86.h index d1d21ed..67c0098 100644 --- a/arch/x86/include/asm/u-boot-x86.h +++ b/arch/x86/include/asm/u-boot-x86.h @@ -8,12 +8,15 @@ #ifndef _U_BOOT_I386_H_ #define _U_BOOT_I386_H_ 1
+extern u32 gdt; + /* cpu/.../cpu.c */ int arch_cpu_init(void); int x86_cpu_init_f(void); int cpu_init_f(void); void init_gd(gd_t *id, u64 *gdt_addr); void setup_gdt(gd_t *id, u64 *gdt_addr); +void setup_fsp_gdt(void); int init_cache(void); int cleanup_before_linux(void);
diff --git a/arch/x86/lib/fsp/fsp_support.c b/arch/x86/lib/fsp/fsp_support.c index 5809235..4585166 100644 --- a/arch/x86/lib/fsp/fsp_support.c +++ b/arch/x86/lib/fsp/fsp_support.c @@ -173,6 +173,9 @@ void fsp_init(u32 stack_top, u32 boot_mode, void *nvs_buf)
post_code(POST_PRE_MRC);
+ /* Load GDT for FSP */ + setup_fsp_gdt(); + /* * Use ASM code to ensure the register value in EAX & ECX * will be passed into BlContinuationFunc
On 06/04 18:28, Bin Meng wrote:
Currently the FSP execution environment GDT is setup by U-Boot in arch/x86/cpu/start16.S, which works pretty well. But if we try to move the FspInitEntry call a little bit later to better fit into U-Boot's initialization sequence, FSP will fail to bring up the AP due to #GP fault as AP's GDT is duplicated from BSP whose GDT is now moved into CAR, and unfortunately FSP calls AP initialization after it disables the CAR. So basically the BSP's GDT still refers to the one in the CAR, whose content is no longer available, so when AP starts up and loads its segment register, it blows up.
To resolve this, we load GDT before calling into FspInitEntry. The GDT is the same one used in arch/x86/cpu/start16.S, which is in the ROM and exists forever.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
Changes in v2:
- Use CONFIG_RESET_SEG_START to avoid duplication
arch/x86/cpu/cpu.c | 20 ++++++++++++++++++++ arch/x86/cpu/start16.S | 1 + arch/x86/include/asm/u-boot-x86.h | 3 +++ arch/x86/lib/fsp/fsp_support.c | 3 +++ 4 files changed, 27 insertions(+)
Tested-by: Andrew Bradford andrew.bradford@kodakalaris.com
Hi Bin,
On 4 June 2015 at 04:28, Bin Meng bmeng.cn@gmail.com wrote:
Currently the FSP execution environment GDT is setup by U-Boot in arch/x86/cpu/start16.S, which works pretty well. But if we try to move the FspInitEntry call a little bit later to better fit into U-Boot's initialization sequence, FSP will fail to bring up the AP due to #GP fault as AP's GDT is duplicated from BSP whose GDT is now moved into CAR, and unfortunately FSP calls AP initialization after it disables the CAR. So basically the BSP's GDT still refers to the one in the CAR, whose content is no longer available, so when AP starts up and loads its segment register, it blows up.
To resolve this, we load GDT before calling into FspInitEntry. The GDT is the same one used in arch/x86/cpu/start16.S, which is in the ROM and exists forever.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
Tested on Minnowboard MAX: Tested-by: Simon Glass sjg@chromium.org
Changes in v2:
- Use CONFIG_RESET_SEG_START to avoid duplication
arch/x86/cpu/cpu.c | 20 ++++++++++++++++++++ arch/x86/cpu/start16.S | 1 + arch/x86/include/asm/u-boot-x86.h | 3 +++ arch/x86/lib/fsp/fsp_support.c | 3 +++ 4 files changed, 27 insertions(+)
diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c index bb4a110..f4ebc97 100644 --- a/arch/x86/cpu/cpu.c +++ b/arch/x86/cpu/cpu.c @@ -164,6 +164,26 @@ void setup_gdt(gd_t *id, u64 *gdt_addr) load_fs(X86_GDT_ENTRY_32BIT_FS); }
+#ifdef CONFIG_HAVE_FSP +/*
- Setup FSP execution environment GDT
- Per Intel FSP external architecture specification, before calling any FSP
- APIs, we need make sure the system is in flat 32-bit mode and both the code
- and data selectors should have full 4GB access range. Here we reuse the one
- we used in arch/x86/cpu/start16.S, and reload the segement registers.
- */
+void setup_fsp_gdt(void) +{
load_gdt((const u64 *)((u32)&gdt + CONFIG_RESET_SEG_START), 4);load_ds(X86_GDT_ENTRY_32BIT_DS);load_ss(X86_GDT_ENTRY_32BIT_DS);load_es(X86_GDT_ENTRY_32BIT_DS);load_fs(X86_GDT_ENTRY_32BIT_DS);load_gs(X86_GDT_ENTRY_32BIT_DS);+} +#endif
int __weak x86_cleanup_before_linux(void) { #ifdef CONFIG_BOOTSTAGE_STASH diff --git a/arch/x86/cpu/start16.S b/arch/x86/cpu/start16.S index 826e2b4..a3e7ab4 100644 --- a/arch/x86/cpu/start16.S +++ b/arch/x86/cpu/start16.S @@ -75,6 +75,7 @@ gdt_ptr:
/* Some CPUs are picky about GDT alignment... */ .align 16+.globl gdt gdt:
Could we rename this to gdt_initial or something like that? To me, gdt is a bit vague for an exported symbol. We need to use a name that indicates it is only used at the start.
/* * The GDT table ...diff --git a/arch/x86/include/asm/u-boot-x86.h b/arch/x86/include/asm/u-boot-x86.h index d1d21ed..67c0098 100644 --- a/arch/x86/include/asm/u-boot-x86.h +++ b/arch/x86/include/asm/u-boot-x86.h @@ -8,12 +8,15 @@ #ifndef _U_BOOT_I386_H_ #define _U_BOOT_I386_H_ 1
+extern u32 gdt;
Perhaps this should be declared as char gdt[] so you don't need to take its address later? See asm/linkage.h for how they do it.
/* cpu/.../cpu.c */ int arch_cpu_init(void); int x86_cpu_init_f(void); int cpu_init_f(void); void init_gd(gd_t *id, u64 *gdt_addr); void setup_gdt(gd_t *id, u64 *gdt_addr); +void setup_fsp_gdt(void);
Please add function comment.
int init_cache(void); int cleanup_before_linux(void);
diff --git a/arch/x86/lib/fsp/fsp_support.c b/arch/x86/lib/fsp/fsp_support.c index 5809235..4585166 100644 --- a/arch/x86/lib/fsp/fsp_support.c +++ b/arch/x86/lib/fsp/fsp_support.c @@ -173,6 +173,9 @@ void fsp_init(u32 stack_top, u32 boot_mode, void *nvs_buf)
post_code(POST_PRE_MRC);
/* Load GDT for FSP */setup_fsp_gdt();/* * Use ASM code to ensure the register value in EAX & ECX * will be passed into BlContinuationFunc-- 1.8.2.1
Regards, Simon
Hi Simon,
On Fri, Jun 5, 2015 at 11:34 PM, Simon Glass sjg@chromium.org wrote:
Hi Bin,
On 4 June 2015 at 04:28, Bin Meng bmeng.cn@gmail.com wrote:
Currently the FSP execution environment GDT is setup by U-Boot in arch/x86/cpu/start16.S, which works pretty well. But if we try to move the FspInitEntry call a little bit later to better fit into U-Boot's initialization sequence, FSP will fail to bring up the AP due to #GP fault as AP's GDT is duplicated from BSP whose GDT is now moved into CAR, and unfortunately FSP calls AP initialization after it disables the CAR. So basically the BSP's GDT still refers to the one in the CAR, whose content is no longer available, so when AP starts up and loads its segment register, it blows up.
To resolve this, we load GDT before calling into FspInitEntry. The GDT is the same one used in arch/x86/cpu/start16.S, which is in the ROM and exists forever.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
Tested on Minnowboard MAX: Tested-by: Simon Glass sjg@chromium.org
Changes in v2:
- Use CONFIG_RESET_SEG_START to avoid duplication
arch/x86/cpu/cpu.c | 20 ++++++++++++++++++++ arch/x86/cpu/start16.S | 1 + arch/x86/include/asm/u-boot-x86.h | 3 +++ arch/x86/lib/fsp/fsp_support.c | 3 +++ 4 files changed, 27 insertions(+)
diff --git a/arch/x86/cpu/cpu.c b/arch/x86/cpu/cpu.c index bb4a110..f4ebc97 100644 --- a/arch/x86/cpu/cpu.c +++ b/arch/x86/cpu/cpu.c @@ -164,6 +164,26 @@ void setup_gdt(gd_t *id, u64 *gdt_addr) load_fs(X86_GDT_ENTRY_32BIT_FS); }
+#ifdef CONFIG_HAVE_FSP +/*
- Setup FSP execution environment GDT
- Per Intel FSP external architecture specification, before calling any FSP
- APIs, we need make sure the system is in flat 32-bit mode and both the code
- and data selectors should have full 4GB access range. Here we reuse the one
- we used in arch/x86/cpu/start16.S, and reload the segement registers.
- */
+void setup_fsp_gdt(void) +{
load_gdt((const u64 *)((u32)&gdt + CONFIG_RESET_SEG_START), 4);load_ds(X86_GDT_ENTRY_32BIT_DS);load_ss(X86_GDT_ENTRY_32BIT_DS);load_es(X86_GDT_ENTRY_32BIT_DS);load_fs(X86_GDT_ENTRY_32BIT_DS);load_gs(X86_GDT_ENTRY_32BIT_DS);+} +#endif
int __weak x86_cleanup_before_linux(void) { #ifdef CONFIG_BOOTSTAGE_STASH diff --git a/arch/x86/cpu/start16.S b/arch/x86/cpu/start16.S index 826e2b4..a3e7ab4 100644 --- a/arch/x86/cpu/start16.S +++ b/arch/x86/cpu/start16.S @@ -75,6 +75,7 @@ gdt_ptr:
/* Some CPUs are picky about GDT alignment... */ .align 16+.globl gdt gdt:
Could we rename this to gdt_initial or something like that? To me, gdt is a bit vague for an exported symbol. We need to use a name that indicates it is only used at the start.
Agreed. How about gdt_rom?
/* * The GDT table ...diff --git a/arch/x86/include/asm/u-boot-x86.h b/arch/x86/include/asm/u-boot-x86.h index d1d21ed..67c0098 100644 --- a/arch/x86/include/asm/u-boot-x86.h +++ b/arch/x86/include/asm/u-boot-x86.h @@ -8,12 +8,15 @@ #ifndef _U_BOOT_I386_H_ #define _U_BOOT_I386_H_ 1
+extern u32 gdt;
Perhaps this should be declared as char gdt[] so you don't need to take its address later? See asm/linkage.h for how they do it.
Good idea!
/* cpu/.../cpu.c */ int arch_cpu_init(void); int x86_cpu_init_f(void); int cpu_init_f(void); void init_gd(gd_t *id, u64 *gdt_addr); void setup_gdt(gd_t *id, u64 *gdt_addr); +void setup_fsp_gdt(void);
Please add function comment.
Sure.
int init_cache(void); int cleanup_before_linux(void);
diff --git a/arch/x86/lib/fsp/fsp_support.c b/arch/x86/lib/fsp/fsp_support.c index 5809235..4585166 100644 --- a/arch/x86/lib/fsp/fsp_support.c +++ b/arch/x86/lib/fsp/fsp_support.c @@ -173,6 +173,9 @@ void fsp_init(u32 stack_top, u32 boot_mode, void *nvs_buf)
post_code(POST_PRE_MRC);
/* Load GDT for FSP */setup_fsp_gdt();/* * Use ASM code to ensure the register value in EAX & ECX * will be passed into BlContinuationFunc--
Regards, Bin
participants (3)
-
Andrew Bradford -
Bin Meng -
Simon Glass