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x86/sev: Do not handle #VC for DR7 read/write

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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 <aik@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Carlos Bilbao <carlos.bilbao@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Link: https://lore.kernel.org/r/20230816022122.981998-1-aik@amd.com
This commit is contained in:
Alexey Kardashevskiy 2023-08-16 12:21:22 +10:00 committed by Borislav Petkov (AMD)
parent 2ccdd1b13c
commit e221804dad
2 changed files with 7 additions and 1 deletions
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2
arch/x86/boot/compressed/sev.c
View File

@ -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)
{

6
arch/x86/kernel/sev.c
View File

@ -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;