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x86/boot: Don't overwrite cr4 when enabling PAE

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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>
This commit is contained in:
Matt Fleming 2014-02-24 13:37:29 +00:00
parent 7d453eee36
commit 108d3f44b1
1 changed files with 2 additions and 1 deletions
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3
arch/x86/boot/compressed/head_64.S
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@ -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
/*