[PATCH Part2 RFC v4 22/40] KVM: SVM: Add KVM_SNP_INIT command

[Brijesh Singh]

The KVM_SNP_INIT command is used by the hypervisor to initialize the
SEV-SNP platform context. In a typical workflow, this command should be the
first command issued. When creating SEV-SNP guest, the VMM must use this
command instead of the KVM_SEV_INIT or KVM_SEV_ES_INIT.

The flags value must be zero, it will be extended in future SNP support to
communicate the optional features (such as restricted INT injection etc).

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
 .../virt/kvm/amd-memory-encryption.rst        | 16 ++++++++
 arch/x86/kvm/svm/sev.c                        | 37 ++++++++++++++++++-
 include/uapi/linux/kvm.h                      |  7 ++++
 3 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index 5c081c8c7164..75ca60b6d40a 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst
@@ -427,6 +427,22 @@ issued by the hypervisor to make the guest ready for execution.
 
 Returns: 0 on success, -negative on error
 
+18. KVM_SNP_INIT
+----------------
+
+The KVM_SNP_INIT command can be used by the hypervisor to initialize SEV-SNP
+context. In a typical workflow, this command should be the first command issued.
+
+Parameters (in): struct kvm_snp_init
+
+Returns: 0 on success, -negative on error
+
+::
+
+        struct kvm_snp_init {
+                __u64 flags;    /* must be zero */
+        };
+
 References
 ==========
 
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index abca2b9dee83..be31221f0a47 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -228,10 +228,24 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
 	sev_guest_decommission(&decommission, NULL);
 }
 
+static int verify_snp_init_flags(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_snp_init params;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+		return -EFAULT;
+
+	if (params.flags)
+		return -EINVAL;
+
+	return 0;
+}
+
 static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
 {
+	bool es_active = (argp->id == KVM_SEV_ES_INIT || argp->id == KVM_SEV_SNP_INIT);
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
-	bool es_active = argp->id == KVM_SEV_ES_INIT;
+	bool snp_active = argp->id == KVM_SEV_SNP_INIT;
 	int asid, ret;
 
 	if (kvm->created_vcpus)
@@ -242,12 +256,22 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		return ret;
 
 	sev->es_active = es_active;
+	sev->snp_active = snp_active;
 	asid = sev_asid_new(sev);
 	if (asid < 0)
 		goto e_no_asid;
 	sev->asid = asid;
 
-	ret = sev_platform_init(&argp->error);
+	if (snp_active) {
+		ret = verify_snp_init_flags(kvm, argp);
+		if (ret)
+			goto e_free;
+
+		ret = sev_snp_init(&argp->error);
+	} else {
+		ret = sev_platform_init(&argp->error);
+	}
+
 	if (ret)
 		goto e_free;
 
@@ -591,6 +615,9 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
 	save->pkru = svm->vcpu.arch.pkru;
 	save->xss  = svm->vcpu.arch.ia32_xss;
 
+	if (sev_snp_guest(svm->vcpu.kvm))
+		save->sev_features |= SVM_SEV_FEATURES_SNP_ACTIVE;
+
 	return 0;
 }
 
@@ -1523,6 +1550,12 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 	}
 
 	switch (sev_cmd.id) {
+	case KVM_SEV_SNP_INIT:
+		if (!sev_snp_enabled) {
+			r = -ENOTTY;
+			goto out;
+		}
+		fallthrough;
 	case KVM_SEV_ES_INIT:
 		if (!sev_es_enabled) {
 			r = -ENOTTY;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 3fd9a7e9d90c..989a64aa1ae5 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1678,6 +1678,9 @@ enum sev_cmd_id {
 	/* Guest Migration Extension */
 	KVM_SEV_SEND_CANCEL,
 
+	/* SNP specific commands */
+	KVM_SEV_SNP_INIT = 256,
+
 	KVM_SEV_NR_MAX,
 };
 
@@ -1774,6 +1777,10 @@ struct kvm_sev_receive_update_data {
 	__u32 trans_len;
 };
 
+struct kvm_snp_init {
+	__u64 flags;
+};
+
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
 #define KVM_DEV_ASSIGN_MASK_INTX	(1 << 2)
-- 
2.17.1