From f0322bd341fd63261527bf84afd3272bcc2e8dd3 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Tue, 29 Jan 2013 16:32:49 -0500 Subject: 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/kernel/cpu/amd.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) (limited to 'arch/x86/kernel/cpu') diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index dd4a5b685a00..721ef3208eb5 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); -- cgit v1.2.3