Messages in this thread Patch in this message | | | From | Matt Fleming <> | Subject | [PATCH 12/13] x86/boot: Don't overwrite cr4 when enabling PAE | Date | Tue, 4 Mar 2014 13:14:20 +0000 |
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From: Matt Fleming <matt.fleming@intel.com>
Some EFI firmware makes use of the FPU during boottime services and clearing X86_CR4_OSFXSR by overwriting %cr4 causes the firmware to crash.
Add the PAE bit explicitly instead of trashing the existing contents, leaving the rest of the bits as the firmware set them.
Cc: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Matt Fleming <matt.fleming@intel.com> --- arch/x86/boot/compressed/head_64.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 37c741b0d2ac..4f40cddd025d 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -113,7 +113,8 @@ ENTRY(startup_32) lgdt gdt(%ebp) /* Enable PAE mode */ - movl $(X86_CR4_PAE), %eax + movl %cr4, %eax + orl $X86_CR4_PAE, %eax movl %eax, %cr4 /* -- 1.8.5.3
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