From f0322bd341fd63261527bf84afd3272bcc2e8dd3 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Tue, 29 Jan 2013 16:32:49 -0500 Subject: [PATCH] x86, AMD: Enable WC+ memory type on family 10 processors In some cases BIOS may not enable WC+ memory type on family 10 processors, instead converting what would be WC+ memory to CD type. On guests using nested pages this could result in performance degradation. This patch enables WC+. Signed-off-by: Boris Ostrovsky Link: http://lkml.kernel.org/r/1359495169-23278-1-git-send-email-ostr@amd64.org Signed-off-by: H. Peter Anvin --- arch/x86/include/uapi/asm/msr-index.h | 1 + arch/x86/kernel/cpu/amd.c | 21 ++++++++++++++++----- 2 files changed, 17 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/uapi/asm/msr-index.h b/arch/x86/include/uapi/asm/msr-index.h index 433a59f..158cde9 100644 --- a/arch/x86/include/uapi/asm/msr-index.h +++ b/arch/x86/include/uapi/asm/msr-index.h @@ -173,6 +173,7 @@ #define MSR_AMD64_OSVW_ID_LENGTH 0xc0010140 #define MSR_AMD64_OSVW_STATUS 0xc0010141 #define MSR_AMD64_DC_CFG 0xc0011022 +#define MSR_AMD64_BU_CFG2 0xc001102a #define MSR_AMD64_IBSFETCHCTL 0xc0011030 #define MSR_AMD64_IBSFETCHLINAD 0xc0011031 #define MSR_AMD64_IBSFETCHPHYSAD 0xc0011032 diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index dd4a5b6..721ef32 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -698,13 +698,11 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c) if (c->x86 > 0x11) set_cpu_cap(c, X86_FEATURE_ARAT); - /* - * Disable GART TLB Walk Errors on Fam10h. We do this here - * because this is always needed when GART is enabled, even in a - * kernel which has no MCE support built in. - */ if (c->x86 == 0x10) { /* + * Disable GART TLB Walk Errors on Fam10h. We do this here + * because this is always needed when GART is enabled, even in a + * kernel which has no MCE support built in. * BIOS should disable GartTlbWlk Errors themself. If * it doesn't do it here as suggested by the BKDG. * @@ -718,6 +716,19 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c) mask |= (1 << 10); wrmsrl_safe(MSR_AMD64_MCx_MASK(4), mask); } + + /* + * On family 10h BIOS may not have properly enabled WC+ support, + * causing it to be converted to CD memtype. This may result in + * performance degradation for certain nested-paging guests. + * Prevent this conversion by clearing bit 24 in + * MSR_AMD64_BU_CFG2. + */ + if (c->x86 == 0x10) { + rdmsrl(MSR_AMD64_BU_CFG2, value); + value &= ~(1ULL << 24); + wrmsrl(MSR_AMD64_BU_CFG2, value); + } } rdmsr_safe(MSR_AMD64_PATCH_LEVEL, &c->microcode, &dummy); -- 2.7.4