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x86, realmode: Mask out EFER.LMA when saving trampoline EFER

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Some AMD processors apparently #GP(0) if EFER.LMA is set in WRMSR,
rather than ignoring it.  Thus, we need to mask it out.

Reported-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Borislav Petkov <bp@alien8.de>
Cc: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1336501366-28617-24-git-send-email-jarkko.sakkinen@intel.com
This commit is contained in:
H. Peter Anvin 2012-05-16 13:22:41 -07:00
parent 34d0b02e08
commit 796038799a
1 changed files with 8 additions and 3 deletions
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11
arch/x86/kernel/realmode.c
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@ -22,6 +22,7 @@ void __init setup_real_mode(void)
size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
#ifdef CONFIG_X86_64
u64 *trampoline_pgd;
u32 efer_low, efer_high;
#endif
/* Has to be in very low memory so we can execute real-mode AP code. */
@ -65,9 +66,13 @@ void __init setup_real_mode(void)
trampoline_header->gdt_limit = __BOOT_DS + 7;
trampoline_header->gdt_base = __pa(boot_gdt);
#else
if (rdmsr_safe(MSR_EFER, &trampoline_header->efer_low,
&trampoline_header->efer_high))
BUG();
/*
* Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
* so we need to mask it out.
*/
rdmsr(MSR_EFER, efer_low, efer_high);
trampoline_header->efer_low = efer_low & ~EFER_LMA;
trampoline_header->efer_high = efer_high;
trampoline_header->start = (u64) secondary_startup_64;
trampoline_cr4_features = &trampoline_header->cr4;