[PATCH Part2 RFC v3 18/37] KVM: SVM: Add initial SEV-SNP support

Brijesh Singh
2021-06-02T14:16:44Z

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
integrity protection to help prevent malicious hypervisor-based attacks
such as data replay, memory re-mapping, and more, to create an isolated
execution environment.

The SNP feature can be enabled in the KVM by passing the sev-snp module
parameter.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/kvm/svm/sev.c | 18 ++++++++++++++++++
arch/x86/kvm/svm/svm.h | 12 ++++++++++++
2 files changed, 30 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 411ed72f63af..abca2b9dee83 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -52,9 +52,14 @@ module_param_named(sev, sev_enabled, bool, 0444);
/* enable/disable SEV-ES support */
static bool sev_es_enabled = true;
module_param_named(sev_es, sev_es_enabled, bool, 0444);
+
+/* enable/disable SEV-SNP support */
+static bool sev_snp_enabled = true;
+module_param_named(sev_snp, sev_snp_enabled, bool, 0444);
#else
#define sev_enabled false
#define sev_es_enabled false
+#define sev_snp_enabled false
#endif /* CONFIG_KVM_AMD_SEV */

#define AP_RESET_HOLD_NONE 0
@@ -1825,6 +1830,7 @@ 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;

@@ -1888,9 +1894,21 @@ void __init sev_hardware_setup(void)
pr_info("SEV-ES supported: %u ASIDs\n", sev_es_asid_count);
sev_es_supported = true;

+ /* SEV-SNP support requested? */
+ if (!sev_snp_enabled)
+ goto out;
+
+ /* Is SEV-SNP enabled? */
+ if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
+ goto out;
+
+ pr_info("SEV-SNP supported: %u ASIDs\n", min_sev_asid - 1);
+ sev_snp_supported = true;
+
out:
sev_enabled = sev_supported;
sev_es_enabled = sev_es_supported;
+ sev_snp_enabled = sev_snp_supported;
#endif
}

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 1175edb02d33..b9ea99f8579e 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -58,6 +58,7 @@ 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 */
@@ -232,6 +233,17 @@ static inline bool sev_es_guest(struct kvm *kvm)
#endif
}

+static inline bool sev_snp_guest(struct kvm *kvm)
+{
+#ifdef CONFIG_KVM_AMD_SEV
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+
+ return sev_es_guest(kvm) && sev->snp_active;
+#else
+ return false;
+#endif
+}
+
static inline void vmcb_mark_all_dirty(struct vmcb *vmcb)
{
vmcb->control.clean = 0;
--
2.17.1