Enhanced SMT Protection (ESMTP) protects an SEV-SNP guest from sibling side channels by requiring that, while a vCPU is in guest mode, its SMT sibling thread is either idle in host mode or executing a vCPU the guest has declared to be a legal sibling.
Add an "esmtp" property to request and use it to advertize this feature for KVM to write it into the launch-time VMSAs. Sample command-line: -object sev-snp-guest,id=sev0,policy=0xb0000,cbitpos=51,reduced-phys-bits=1,esmtp=on Signed-off-by: Pratik R. Sampat <[email protected]> --- qapi/qom.json | 9 ++++++++- target/i386/sev.c | 15 +++++++++++++++ target/i386/sev.h | 1 + 3 files changed, 24 insertions(+), 1 deletion(-) diff --git a/qapi/qom.json b/qapi/qom.json index 4a9b7f908844..010c5cc2bb82 100644 --- a/qapi/qom.json +++ b/qapi/qom.json @@ -1119,6 +1119,12 @@ # @tsc-frequency: set secure TSC frequency. Only valid if Secure TSC # is enabled (default: zero) (since 11.1) # +# @esmtp: Enable Enhanced SMT Protection support for the guest. Adds +# corresponding VMSA feature bit to KVM_SEV_INIT2 vmsa_features so +# the host applies it to each vCPU's VMSA. Opt-in feature as it +# provides additional protection but with runtime overhead. +# (default: false) (since 11.2) +# # Since: 9.1 ## { 'struct': 'SevSnpGuestProperties', @@ -1132,7 +1138,8 @@ '*host-data': 'str', '*vcek-disabled': 'bool', '*secure-tsc': 'bool', - '*tsc-frequency': 'uint32' } } + '*tsc-frequency': 'uint32', + '*esmtp': 'bool' } } ## # @TdxGuestProperties: diff --git a/target/i386/sev.c b/target/i386/sev.c index cc16c6b07123..0b5767057175 100644 --- a/target/i386/sev.c +++ b/target/i386/sev.c @@ -3255,6 +3255,18 @@ sev_snp_guest_set_tsc_frequency(Object *obj, Visitor *v, const char *name, SEV_SNP_GUEST(obj)->tsc_khz = value / 1000; } +static bool +sev_snp_guest_get_esmtp(Object *obj, Error **errp) +{ + return is_sev_feature_set(SEV_COMMON(obj), SVM_SEV_FEAT_ESMTP); +} + +static void +sev_snp_guest_set_esmtp(Object *obj, bool value, Error **errp) +{ + sev_set_feature(SEV_COMMON(obj), SVM_SEV_FEAT_ESMTP, value); +} + static void sev_snp_guest_class_init(ObjectClass *oc, const void *data) { @@ -3296,6 +3308,9 @@ sev_snp_guest_class_init(ObjectClass *oc, const void *data) object_class_property_add(oc, "tsc-frequency", "uint32", sev_snp_guest_get_tsc_frequency, sev_snp_guest_set_tsc_frequency, NULL, NULL); + object_class_property_add_bool(oc, "esmtp", + sev_snp_guest_get_esmtp, + sev_snp_guest_set_esmtp); } static void diff --git a/target/i386/sev.h b/target/i386/sev.h index 7725f92e1959..6b4128dea4ae 100644 --- a/target/i386/sev.h +++ b/target/i386/sev.h @@ -49,6 +49,7 @@ bool sev_snp_enabled(void); #define SVM_SEV_FEAT_SNP_ACTIVE BIT(0) #define SVM_SEV_FEAT_DEBUG_SWAP BIT(5) #define SVM_SEV_FEAT_SECURE_TSC BIT(9) +#define SVM_SEV_FEAT_ESMTP BIT(17) typedef struct SevKernelLoaderContext { char *setup_data; -- 2.43.0
