Version 2 of the GHCB specification added the advertisement of features
that are supported by the hypervisor. If hypervisor supports the SEV-SNP
then it must set the SEV-SNP features bit to indicate that the base
SEV-SNP is supported.
Check the SEV-SNP feature while establishing the GHCB, if failed,
terminate the guest.
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
arch/x86/boot/compressed/sev.c | 17 +++++++++++++++--
arch/x86/include/asm/sev-common.h | 3 +++
arch/x86/kernel/sev.c | 12 ++++++++++--
3 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 78f8502e09b5..e525fa74a551 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -119,11 +119,24 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
/* Include code for early handlers */
#include "../../kernel/sev-shared.c"
-static bool early_setup_sev_es(void)
+static inline bool sev_snp_enabled(void)
+{
+ return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
+}
+
+static bool do_early_sev_setup(void)
{
if (!sev_es_negotiate_protocol())
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
+ /*
+ * SNP is supported in v2 of the GHCB spec which mandates support for HV
+ * features. If SEV-SNP is enabled, then check if the hypervisor supports
+ * the SEV-SNP features.
+ */
+ if (sev_snp_enabled() && !(sev_hv_features & GHCB_HV_FT_SNP))
+ sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
+
if (set_page_decrypted((unsigned long)&boot_ghcb_page))
return false;
@@ -174,7 +187,7 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
struct es_em_ctxt ctxt;
enum es_result result;
- if (!boot_ghcb && !early_setup_sev_es())
+ if (!boot_ghcb && !do_early_sev_setup())
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
vc_ghcb_invalidate(boot_ghcb);
diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index 891569c07ed7..f80a3cde2086 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -64,6 +64,8 @@
/* GHCBData[63:12] */ \
(((u64)(v) & GENMASK_ULL(63, 12)) >> 12)
+#define GHCB_HV_FT_SNP BIT_ULL(0)
+
#define GHCB_MSR_TERM_REQ 0x100
#define GHCB_MSR_TERM_REASON_SET_POS 12
#define GHCB_MSR_TERM_REASON_SET_MASK 0xf
@@ -80,6 +82,7 @@
#define SEV_TERM_SET_GEN 0
#define GHCB_SEV_ES_GEN_REQ 0
#define GHCB_SEV_ES_PROT_UNSUPPORTED 1
+#define GHCB_SNP_UNSUPPORTED 2
/* Linux-specific reason codes (used with reason set 1) */
#define SEV_TERM_SET_LINUX 1
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index fb48e4ddd474..80a41e413cb8 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -627,12 +627,20 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
* This function runs on the first #VC exception after the kernel
* switched to virtual addresses.
*/
-static bool __init sev_es_setup_ghcb(void)
+static bool __init setup_ghcb(void)
{
/* First make sure the hypervisor talks a supported protocol. */
if (!sev_es_negotiate_protocol())
return false;
+ /*
+ * SNP is supported in v2 of the GHCB spec which mandates support for HV
+ * features. If SEV-SNP is enabled, then check if the hypervisor supports
+ * the SEV-SNP features.
+ */
+ if (cc_platform_has(CC_ATTR_SEV_SNP) && !(sev_hv_features & GHCB_HV_FT_SNP))
+ sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
+
/*
* Clear the boot_ghcb. The first exception comes in before the bss
* section is cleared.
@@ -1453,7 +1461,7 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
enum es_result result;
/* Do initial setup or terminate the guest */
- if (unlikely(boot_ghcb == NULL && !sev_es_setup_ghcb()))
+ if (unlikely(!boot_ghcb && !setup_ghcb()))
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
vc_ghcb_invalidate(boot_ghcb);
--
2.25.1
