The hypervisor should not be intercepting RDTSC/RDTSCP when Secure TSC is enabled. A #VC exception will be generated if the RDTSC/RDTSCP instructions are being intercepted. If this should occur and Secure TSC is enabled, guest execution should be terminated as the guest cannot rely on the TSC value provided by the hypervisor. Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx> Tested-by: Peter Gonda <pgonda@xxxxxxxxxx> Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx> --- arch/x86/coco/sev/shared.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/coco/sev/shared.c b/arch/x86/coco/sev/shared.c index 96023bd978cc..2e4122f8aa6b 100644 --- a/arch/x86/coco/sev/shared.c +++ b/arch/x86/coco/sev/shared.c @@ -1141,6 +1141,16 @@ static enum es_result vc_handle_rdtsc(struct ghcb *ghcb, bool rdtscp = (exit_code == SVM_EXIT_RDTSCP); enum es_result ret; + /* + * The hypervisor should not be intercepting RDTSC/RDTSCP when Secure + * TSC is enabled. A #VC exception will be generated if the RDTSC/RDTSCP + * instructions are being intercepted. If this should occur and Secure + * TSC is enabled, guest execution should be terminated as the guest + * cannot rely on the TSC value provided by the hypervisor. + */ + if (sev_status & MSR_AMD64_SNP_SECURE_TSC) + return ES_VMM_ERROR; + ret = sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, 0, 0); if (ret != ES_OK) return ret; -- 2.34.1
