Hi Heinrich,
On Fri, Oct 12, 2018 at 2:04 AM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
On 10/11/2018 03:53 AM, Bin Meng wrote:
With the '-march=core2' fix, it seems that we have some luck that the 64-bit U-Boot boots again. However if we examine the disassembly codes there are still SSE instructions elsewhere which means passing cpu type to GCC is not enough to prevent it from generating these instructions. A simple test case is doing a 'bootefi selftest' from the U-Boot shell and it leads to a reset too.
I can confirm that an unexpected reset patch occurs without the patch.
I think you mean "bootefi selftest" reset, right?
The 'bootefi selftest' reset is even seen with the image created by the relative older GCC 5.4.0, the one shipped by Ubuntu 16.04.
To make sure no MMX/SSE instruction sets are generated, tell GCC not to do this. Note AVX is out of the question as CORE2 is old enough to support AVX yet.
Signed-off-by: Bin Meng bmeng.cn@gmail.com
arch/x86/config.mk | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/x86/config.mk b/arch/x86/config.mk index 576501e..8151e47 100644 --- a/arch/x86/config.mk +++ b/arch/x86/config.mk @@ -24,6 +24,7 @@ ifeq ($(IS_32BIT),y) PLATFORM_CPPFLAGS += -march=i386 -m32 else PLATFORM_CPPFLAGS += $(if $(CONFIG_SPL_BUILD),,-fpic) -fno-common -march=core2 -m64 +PLATFORM_CPPFLAGS += -mno-mmx -mno-sse
According to https://wiki.osdev.org/SSE SSE has to be initialized. Otherwise SSE instructions lead to an undefined instruction exception. Is it this initialization that we lack? If this is your motivation please, state it in the commit message.
Yes, it's intentional. U-Boot as a bootloader does not want to handle these advanced SIMD stuff.
I think this patch could be squashed with the prior one.
They are different thing, although they solved similar reset. The first patch is adding the -march=core2 which is the counterpart of -march=i386 for 32-bit U-Boot. This patch is to disable MMX/SSE completely which I think deserve a separate patch.
Regards, Bin