From e221804dad4e6fe3a0cf192ba3c42cd2f328bdac Mon Sep 17 00:00:00 2001 From: Alexey Kardashevskiy Date: Wed, 16 Aug 2023 12:21:22 +1000 Subject: [PATCH] x86/sev: Do not handle #VC for DR7 read/write With MSR_AMD64_SEV_DEBUG_SWAP enabled, the guest is not expected to receive a #VC for reads or writes of DR7. Update the SNP_FEATURES_PRESENT mask with MSR_AMD64_SNP_DEBUG_SWAP so an SNP guest doesn't gracefully terminate during SNP feature negotiation if MSR_AMD64_SEV_DEBUG_SWAP is enabled. Since a guest is not expected to receive a #VC on DR7 accesses when MSR_AMD64_SEV_DEBUG_SWAP is enabled, return an error from the #VC handler in this situation. Signed-off-by: Alexey Kardashevskiy Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Carlos Bilbao Reviewed-by: Tom Lendacky Reviewed-by: Pankaj Gupta Link: https://lore.kernel.org/r/20230816022122.981998-1-aik@amd.com --- arch/x86/boot/compressed/sev.c | 2 +- arch/x86/kernel/sev.c | 6 ++++++ 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c index c3e343bd4760e..e83e71089cf1c 100644 --- a/arch/x86/boot/compressed/sev.c +++ b/arch/x86/boot/compressed/sev.c @@ -365,7 +365,7 @@ static void enforce_vmpl0(void) * by the guest kernel. As and when a new feature is implemented in the * guest kernel, a corresponding bit should be added to the mask. */ -#define SNP_FEATURES_PRESENT (0) +#define SNP_FEATURES_PRESENT MSR_AMD64_SNP_DEBUG_SWAP void snp_check_features(void) { diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 1ee7bed453ded..d380c93994802 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -1575,6 +1575,9 @@ static enum es_result vc_handle_dr7_write(struct ghcb *ghcb, long val, *reg = vc_insn_get_rm(ctxt); enum es_result ret; + if (sev_status & MSR_AMD64_SNP_DEBUG_SWAP) + return ES_VMM_ERROR; + if (!reg) return ES_DECODE_FAILED; @@ -1612,6 +1615,9 @@ static enum es_result vc_handle_dr7_read(struct ghcb *ghcb, struct sev_es_runtime_data *data = this_cpu_read(runtime_data); long *reg = vc_insn_get_rm(ctxt); + if (sev_status & MSR_AMD64_SNP_DEBUG_SWAP) + return ES_VMM_ERROR; + if (!reg) return ES_DECODE_FAILED; -- 2.30.2