x86, realmode: Mask out EFER.LMA when saving trampoline EFER
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
diff --git a/arch/x86/kernel/realmode.c b/arch/x86/kernel/realmode.c
index 66ac276..0992779 100644
--- a/arch/x86/kernel/realmode.c
+++ b/arch/x86/kernel/realmode.c
@@ -22,6 +22,7 @@
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 @@
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;