From e05139f2569ecf699b229a6473a86cdffed62956 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Wed, 28 Sep 2011 16:56:51 +0100 Subject: [PATCH] x86-64: Don't apply destructive erratum workaround on unaffected CPUs Erratum 93 applies to AMD K8 CPUs only, and its workaround (forcing the upper 32 bits of %rip to all get set under certain conditions) is actually getting in the way of analyzing page faults occurring during EFI physical mode runtime calls (in particular the page table walk shown is completely unrelated to the actual fault). This is because typically EFI runtime code lives in the space between 2G and 4G, which - modulo the above manipulation - is likely to overlap with the kernel or modules area. While even for the other errata workarounds their taking effect could be limited to just the affected CPUs, none of them appears to be destructive, and they're generally getting called only outside of performance critical paths, so they're being left untouched. Signed-off-by: Jan Beulich Link: http://lkml.kernel.org/r/4E835FE30200007800058464@nat28.tlf.novell.com Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 0d17c8c..9c7378d 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -420,12 +420,14 @@ static noinline __kprobes int vmalloc_fault(unsigned long address) return 0; } +#ifdef CONFIG_CPU_SUP_AMD static const char errata93_warning[] = KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n" "******* Working around it, but it may cause SEGVs or burn power.\n" "******* Please consider a BIOS update.\n" "******* Disabling USB legacy in the BIOS may also help.\n"; +#endif /* * No vm86 mode in 64-bit mode: @@ -505,7 +507,11 @@ bad: */ static int is_errata93(struct pt_regs *regs, unsigned long address) { -#ifdef CONFIG_X86_64 +#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) + if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD + || boot_cpu_data.x86 != 0xf) + return 0; + if (address != regs->ip) return 0; -- 2.7.4