linux-kernel - [PATCH Part2 RFC v2 19/37] KVM: SVM: Add initial SEV-SNP support

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Date:   Fri, 30 Apr 2021 07:38:04 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     tglx@...utronix.de, bp@...en8.de, jroedel@...e.de,
        thomas.lendacky@....com, pbonzini@...hat.com, mingo@...hat.com,
        dave.hansen@...el.com, rientjes@...gle.com, seanjc@...gle.com,
        peterz@...radead.org, hpa@...or.com, tony.luck@...el.com,
        Brijesh Singh <brijesh.singh@....com>
Subject: [PATCH Part2 RFC v2 19/37] KVM: SVM: Add initial SEV-SNP support

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@....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 b750e435626a..200d227f9232 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
@@ -1826,6 +1831,7 @@ 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;
 
@@ -1889,9 +1895,21 @@ 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 894e828227d9..85a2d5857ffb 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