[PATCH v11 14/35] KVM: SEV: Add initial SEV-SNP support

Michael Roth
2023-12-30T17:26:29Z

From: Brijesh Singh <brijesh.singh@amd.com>

The next generation of SEV is called SEV-SNP (Secure Nested Paging).
SEV-SNP builds upon existing SEV and SEV-ES functionality while adding
new hardware-based security protection. SEV-SNP adds strong memory
encryption and integrity protection to help prevent malicious
hypervisor-based attacks such as data replay, memory re-mapping, and
more, to create an isolated execution environment.

Implement some initial infrastructure in KVM to check/report when SNP is
enabled on the system.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
[mdr: commit fixups, use similar ASID reporting as with SEV/SEV-ES]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
arch/x86/kvm/svm/sev.c | 10 ++++++++++
arch/x86/kvm/svm/svm.h | 8 ++++++++
2 files changed, 18 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index d6e206d21750..18c09863377b 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -59,10 +59,13 @@ module_param_named(sev_es, sev_es_enabled, bool, 0444);
/* enable/disable SEV-ES DebugSwap support */
static bool sev_es_debug_swap_enabled = true;
module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
+
+static bool sev_snp_enabled;
#else
#define sev_enabled false
#define sev_es_enabled false
#define sev_es_debug_swap_enabled false
+#define sev_snp_enabled false
#endif /* CONFIG_KVM_AMD_SEV */

#define AP_RESET_HOLD_NONE 0
@@ -2189,6 +2192,7 @@ void __init sev_hardware_setup(void)
{
#ifdef CONFIG_KVM_AMD_SEV
unsigned int eax, ebx, ecx, edx, sev_asid_count, sev_es_asid_count;
+ bool sev_snp_supported = false;
bool sev_es_supported = false;
bool sev_supported = false;

@@ -2267,6 +2271,7 @@ void __init sev_hardware_setup(void)
sev_es_asid_count = min_sev_asid - 1;
WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count));
sev_es_supported = true;
+ sev_snp_supported = sev_snp_enabled && cpu_feature_enabled(X86_FEATURE_SEV_SNP);

out:
if (boot_cpu_has(X86_FEATURE_SEV))
@@ -2277,12 +2282,17 @@ void __init sev_hardware_setup(void)
pr_info("SEV-ES %s (ASIDs %u - %u)\n",
sev_es_supported ? "enabled" : "disabled",
min_sev_asid > 1 ? 1 : 0, min_sev_asid - 1);
+ if (boot_cpu_has(X86_FEATURE_SEV_SNP))
+ pr_info("SEV-SNP %s (ASIDs %u - %u)\n",
+ sev_snp_supported ? "enabled" : "disabled",
+ min_sev_asid > 1 ? 1 : 0, min_sev_asid - 1);

sev_enabled = sev_supported;
sev_es_enabled = sev_es_supported;
if (!sev_es_enabled || !cpu_feature_enabled(X86_FEATURE_DEBUG_SWAP) ||
!cpu_feature_enabled(X86_FEATURE_NO_NESTED_DATA_BP))
sev_es_debug_swap_enabled = false;
+ sev_snp_enabled = sev_snp_supported;
#endif
}

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index d0f8167ada7c..a3e27c82866b 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -79,6 +79,7 @@ enum {
struct kvm_sev_info {
bool active; /* SEV enabled guest */
bool es_active; /* SEV-ES enabled guest */
+ bool snp_active; /* SEV-SNP enabled guest */
unsigned int asid; /* ASID used for this guest */
unsigned int handle; /* SEV firmware handle */
int fd; /* SEV device fd */
@@ -341,6 +342,13 @@ static __always_inline bool sev_es_guest(struct kvm *kvm)
#endif
}

+static __always_inline bool sev_snp_guest(struct kvm *kvm)
+{
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+
+ return sev_es_guest(kvm) && sev->snp_active;
+}
+
static inline void vmcb_mark_all_dirty(struct vmcb *vmcb)
{
vmcb->control.clean = 0;
--
2.25.1