From: Boris Ostrovsky Date: Fri, 18 Jan 2013 11:20:58 +0000 (+0100) Subject: x86/AMD: Enable WC+ memory type on family 10 processors X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=d3f3afe72d93afb0b9b88f913c925c0ce45c0eee;p=people%2Faperard%2Fxen-arm.git 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 Committed-by: Jan Beulich --- diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c index b8d4a2abba..27b7f71d8b 100644 --- a/xen/arch/x86/cpu/amd.c +++ b/xen/arch/x86/cpu/amd.c @@ -485,6 +485,17 @@ static void __devinit init_amd(struct cpuinfo_x86 *c) check_enable_amd_mmconf_dmi(); fam10h_check_enable_mmcfg(); + + /* + * 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_F10_BU_CFG2. + */ + rdmsrl(MSR_F10_BU_CFG2, value); + value &= ~(1ULL << 24); + wrmsrl(MSR_F10_BU_CFG2, value); } /* diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h index 03f6f985b0..5c1de6e096 100644 --- a/xen/include/asm-x86/msr-index.h +++ b/xen/include/asm-x86/msr-index.h @@ -220,8 +220,9 @@ #define MSR_F10_MC4_MISC2 0xc0000409 #define MSR_F10_MC4_MISC3 0xc000040A -/* AMD Family10h MMU control MSRs */ -#define MSR_F10_BU_CFG 0xc0011023 +/* AMD Family10h Bus Unit MSRs */ +#define MSR_F10_BU_CFG 0xc0011023 +#define MSR_F10_BU_CFG2 0xc001102a /* Other AMD Fam10h MSRs */ #define MSR_FAM10H_MMIO_CONF_BASE 0xc0010058