On 9/9/21 10:32 PM, Marc Orr wrote:

On Fri, Aug 20, 2021 at 9:00 AM Brijesh Singh [off-list ref] wrote:

quoted

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).

Co-developed-by: Pavan Kumar Paluri <redacted>
Signed-off-by: Pavan Kumar Paluri <redacted>
Signed-off-by: Brijesh Singh <redacted>
---
 .../virt/kvm/amd-memory-encryption.rst        | 27 ++++++++++++
 arch/x86/include/asm/svm.h                    |  2 +
 arch/x86/kvm/svm/sev.c                        | 44 ++++++++++++++++++-
 arch/x86/kvm/svm/svm.h                        |  4 ++
 include/uapi/linux/kvm.h                      | 13 ++++++
 5 files changed, 88 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index 5c081c8c7164..7b1d32fb99a8 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst

@@ -427,6 +427,33 @@ 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/out): struct kvm_snp_init
+
+Returns: 0 on success, -negative on error
+
+::
+
+        struct kvm_snp_init {
+                __u64 flags;
+        };
+
+The flags bitmap is defined as::
+
+   /* enable the restricted injection */
+   #define KVM_SEV_SNP_RESTRICTED_INJET   (1<<0)
+
+   /* enable the restricted injection timer */
+   #define KVM_SEV_SNP_RESTRICTED_TIMER_INJET   (1<<1)
+
+If the specified flags is not supported then return -EOPNOTSUPP, and the supported
+flags are returned.
+
 References
 ==========

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index 44a3f920f886..a39e31845a33 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h

@@ -218,6 +218,8 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 #define SVM_NESTED_CTL_SEV_ENABLE      BIT(1)
 #define SVM_NESTED_CTL_SEV_ES_ENABLE   BIT(2)

+#define SVM_SEV_FEAT_SNP_ACTIVE                BIT(0)
+
 struct vmcb_seg {
        u16 selector;
        u16 attrib;

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 50fddbe56981..93da463545ef 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c

@@ -235,10 +235,30 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
        sev_decommission(handle);
 }

+static int verify_snp_init_flags(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+       struct kvm_snp_init params;
+       int ret = 0;
+
+       if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+               return -EFAULT;
+
+       if (params.flags & ~SEV_SNP_SUPPORTED_FLAGS)
+               ret = -EOPNOTSUPP;
+
+       params.flags = SEV_SNP_SUPPORTED_FLAGS;
+
+       if (copy_to_user((void __user *)(uintptr_t)argp->data, &params, sizeof(params)))
+               ret = -EFAULT;
+
+       return ret;
+}
+
 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)

@@ -249,12 +269,22 @@ 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;

@@ -600,6 +630,10 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
        save->pkru = svm->vcpu.arch.pkru;
        save->xss  = svm->vcpu.arch.ia32_xss;

+       /* Enable the SEV-SNP feature */
+       if (sev_snp_guest(svm->vcpu.kvm))
+               save->sev_features |= SVM_SEV_FEAT_SNP_ACTIVE;
+
        return 0;
 }

@@ -1532,6 +1566,12 @@ 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/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 01953522097d..57c3c404b0b3 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h

@@ -69,6 +69,9 @@ enum {
 /* TPR and CR2 are always written before VMRUN */
 #define VMCB_ALWAYS_DIRTY_MASK ((1U << VMCB_INTR) | (1U << VMCB_CR2))

+/* Supported init feature flags */
+#define SEV_SNP_SUPPORTED_FLAGS                0x0
+
 struct kvm_sev_info {
        bool active;            /* SEV enabled guest */
        bool es_active;         /* SEV-ES enabled guest */

@@ -81,6 +84,7 @@ struct kvm_sev_info {
        u64 ap_jump_table;      /* SEV-ES AP Jump Table address */
        struct kvm *enc_context_owner; /* Owner of copied encryption context */
        struct misc_cg *misc_cg; /* For misc cgroup accounting */
+       u64 snp_init_flags;

This field never gets set anywhere. Should it get set in
`verify_snp_init_flags()`?

Actually the supported flag value is zero, so didn't update it. But to
make code cleaner I will set the flag after the negotiation.

quoted

 };

 struct kvm_svm {

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d9e4aabcb31a..944e2bf601fe 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h

@@ -1712,6 +1712,9 @@ enum sev_cmd_id {
        /* Guest Migration Extension */
        KVM_SEV_SEND_CANCEL,

+       /* SNP specific commands */
+       KVM_SEV_SNP_INIT,
+
        KVM_SEV_NR_MAX,
 };

@@ -1808,6 +1811,16 @@ struct kvm_sev_receive_update_data {
        __u32 trans_len;
 };

+/* enable the restricted injection */
+#define KVM_SEV_SNP_RESTRICTED_INJET   (1 << 0)
+
+/* enable the restricted injection timer */
+#define KVM_SEV_SNP_RESTRICTED_TIMER_INJET   (1 << 1)
+
+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