From: Andrew Cooper Subject: x86/spec-ctrl: CPUID/MSR definitions for Microarchitectural Data Sampling The MD_CLEAR feature can be automatically offered to guests. No infrastructure is needed in Xen to support the guest making use of it. This is part of XSA-297, CVE-2018-12126, CVE-2018-12127, CVE-2018-12130, CVE-2019-11091. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown index 10ed971..a74a995 100644 --- a/docs/misc/xen-command-line.markdown +++ b/docs/misc/xen-command-line.markdown @@ -456,7 +456,7 @@ accounting for hardware capabilities as enumerated via CPUID. Currently accepted: -The Speculation Control hardware features `ibrsb`, `stibp`, `ibpb`, +The Speculation Control hardware features `md-clear`, `ibrsb`, `stibp`, `ibpb`, `l1d-flush` and `ssbd` are used by default if available and applicable. They can be ignored, e.g. `no-ibrsb`, at which point Xen won't use them itself, and won't offer them to guests. diff --git a/tools/libxl/libxl_cpuid.c b/tools/libxl/libxl_cpuid.c index d0f4eeb..20d0602 100644 --- a/tools/libxl/libxl_cpuid.c +++ b/tools/libxl/libxl_cpuid.c @@ -158,6 +158,7 @@ int libxl_cpuid_parse_config(libxl_cpuid_policy_list *cpuid, const char* str) {"de", 0x00000001, NA, CPUID_REG_EDX, 2, 1}, {"vme", 0x00000001, NA, CPUID_REG_EDX, 1, 1}, {"fpu", 0x00000001, NA, CPUID_REG_EDX, 0, 1}, + {"md-clear", 0x00000007, 0, CPUID_REG_EDX, 10, 1}, {"ibrsb", 0x00000007, 0, CPUID_REG_EDX, 26, 1}, {"stibp", 0x00000007, 0, CPUID_REG_EDX, 27, 1}, {"l1d-flush", 0x00000007, 0, CPUID_REG_EDX, 28, 1}, diff --git a/tools/misc/xen-cpuid.c b/tools/misc/xen-cpuid.c index 702c072..72c67d0 100644 --- a/tools/misc/xen-cpuid.c +++ b/tools/misc/xen-cpuid.c @@ -157,8 +157,9 @@ static const char *str_7d0[32] = [ 2] = "avx512_4vnniw", [ 3] = "avx512_4fmaps", - [4 ... 11] = "REZ", + [4 ... 9] = "REZ", + [10] = "md-clear", [11] = "REZ", [12] = "REZ", [13] = "tsx-force-abort", [14 ... 25] = "REZ", diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c index 0f59cd6..2201f8a 100644 --- a/xen/arch/x86/cpuid.c +++ b/xen/arch/x86/cpuid.c @@ -28,7 +28,12 @@ static int __init parse_xen_cpuid(const char *s) if ( !ss ) ss = strchr(s, '\0'); - if ( (val = parse_boolean("ibpb", s, ss)) >= 0 ) + if ( (val = parse_boolean("md-clear", s, ss)) >= 0 ) + { + if ( !val ) + setup_clear_cpu_cap(X86_FEATURE_MD_CLEAR); + } + else if ( (val = parse_boolean("ibpb", s, ss)) >= 0 ) { if ( !val ) setup_clear_cpu_cap(X86_FEATURE_IBPB); diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c index 2a7267c..4e6558a 100644 --- a/xen/arch/x86/spec_ctrl.c +++ b/xen/arch/x86/spec_ctrl.c @@ -330,17 +330,19 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps) printk("Speculative mitigation facilities:\n"); /* Hardware features which pertain to speculative mitigations. */ - printk(" Hardware features:%s%s%s%s%s%s%s%s%s%s\n", + printk(" Hardware features:%s%s%s%s%s%s%s%s%s%s%s%s\n", (_7d0 & cpufeat_mask(X86_FEATURE_IBRSB)) ? " IBRS/IBPB" : "", (_7d0 & cpufeat_mask(X86_FEATURE_STIBP)) ? " STIBP" : "", (_7d0 & cpufeat_mask(X86_FEATURE_L1D_FLUSH)) ? " L1D_FLUSH" : "", (_7d0 & cpufeat_mask(X86_FEATURE_SSBD)) ? " SSBD" : "", + (_7d0 & cpufeat_mask(X86_FEATURE_MD_CLEAR)) ? " MD_CLEAR" : "", (e8b & cpufeat_mask(X86_FEATURE_IBPB)) ? " IBPB" : "", (caps & ARCH_CAPABILITIES_IBRS_ALL) ? " IBRS_ALL" : "", (caps & ARCH_CAPABILITIES_RDCL_NO) ? " RDCL_NO" : "", (caps & ARCH_CAPS_RSBA) ? " RSBA" : "", (caps & ARCH_CAPS_SKIP_L1DFL) ? " SKIP_L1DFL": "", - (caps & ARCH_CAPS_SSB_NO) ? " SSB_NO" : ""); + (caps & ARCH_CAPS_SSB_NO) ? " SSB_NO" : "", + (caps & ARCH_CAPS_MDS_NO) ? " MDS_NO" : ""); /* Compiled-in support which pertains to mitigations. */ if ( IS_ENABLED(CONFIG_INDIRECT_THUNK) || IS_ENABLED(CONFIG_SHADOW_PAGING) ) @@ -377,19 +379,21 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps) * Alternatives blocks for protecting against and/or virtualising * mitigation support for guests. */ - printk(" Support for VMs: PV:%s%s%s%s, HVM:%s%s%s%s\n", + printk(" Support for VMs: PV:%s%s%s%s%s, HVM:%s%s%s%s%s\n", (boot_cpu_has(X86_FEATURE_SC_MSR_PV) || boot_cpu_has(X86_FEATURE_SC_RSB_PV) || opt_eager_fpu) ? "" : " None", boot_cpu_has(X86_FEATURE_SC_MSR_PV) ? " MSR_SPEC_CTRL" : "", boot_cpu_has(X86_FEATURE_SC_RSB_PV) ? " RSB" : "", opt_eager_fpu ? " EAGER_FPU" : "", + boot_cpu_has(X86_FEATURE_MD_CLEAR) ? " MD_CLEAR" : "", (boot_cpu_has(X86_FEATURE_SC_MSR_HVM) || boot_cpu_has(X86_FEATURE_SC_RSB_HVM) || opt_eager_fpu) ? "" : " None", boot_cpu_has(X86_FEATURE_SC_MSR_HVM) ? " MSR_SPEC_CTRL" : "", boot_cpu_has(X86_FEATURE_SC_RSB_HVM) ? " RSB" : "", - opt_eager_fpu ? " EAGER_FPU" : ""); + opt_eager_fpu ? " EAGER_FPU" : "", + boot_cpu_has(X86_FEATURE_MD_CLEAR) ? " MD_CLEAR" : ""); printk(" XPTI (64-bit PV only): Dom0 %s, DomU %s\n", opt_xpti_hwdom ? "enabled" : "disabled", diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h index bc72476..92d9ee7 100644 --- a/xen/include/asm-x86/msr-index.h +++ b/xen/include/asm-x86/msr-index.h @@ -53,6 +53,7 @@ #define ARCH_CAPS_RSBA (_AC(1, ULL) << 2) #define ARCH_CAPS_SKIP_L1DFL (_AC(1, ULL) << 3) #define ARCH_CAPS_SSB_NO (_AC(1, ULL) << 4) +#define ARCH_CAPS_MDS_NO (_AC(1, ULL) << 5) #define MSR_FLUSH_CMD 0x0000010b #define FLUSH_CMD_L1D (_AC(1, ULL) << 0) diff --git a/xen/include/public/arch-x86/cpufeatureset.h b/xen/include/public/arch-x86/cpufeatureset.h index 33b515e..000a941 100644 --- a/xen/include/public/arch-x86/cpufeatureset.h +++ b/xen/include/public/arch-x86/cpufeatureset.h @@ -241,6 +241,7 @@ XEN_CPUFEATURE(IBPB, 8*32+12) /*A IBPB support only (no IBRS, used by /* Intel-defined CPU features, CPUID level 0x00000007:0.edx, word 9 */ XEN_CPUFEATURE(AVX512_4VNNIW, 9*32+ 2) /*A AVX512 Neural Network Instructions */ XEN_CPUFEATURE(AVX512_4FMAPS, 9*32+ 3) /*A AVX512 Multiply Accumulation Single Precision */ +XEN_CPUFEATURE(MD_CLEAR, 9*32+10) /*A VERW clears microarchitectural buffers */ XEN_CPUFEATURE(TSX_FORCE_ABORT, 9*32+13) /* MSR_TSX_FORCE_ABORT.RTM_ABORT */ XEN_CPUFEATURE(IBRSB, 9*32+26) /*A IBRS and IBPB support (used by Intel) */ XEN_CPUFEATURE(STIBP, 9*32+27) /*A STIBP */