[PATCH RFC v8 33/56] KVM: SVM: Add KVM_SNP_INIT command

From: Michael Roth
Date: Mon Feb 20 2023 - 13:54:22 EST

From: Brijesh Singh <brijesh.singh@xxxxxxx>

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 <papaluri@xxxxxxx>
Signed-off-by: Pavan Kumar Paluri <papaluri@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
.../virt/kvm/x86/amd-memory-encryption.rst | 27 ++++++++++++
arch/x86/include/asm/svm.h | 1 +
arch/x86/kvm/svm/sev.c | 44 ++++++++++++++++++-
arch/x86/kvm/svm/svm.h | 4 ++
include/uapi/linux/kvm.h | 13 ++++++
5 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
index 935aaeb97fe6..2432213bd0ea 100644
--- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
@@ -434,6 +434,33 @@ 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 cb1ee53ad3b1..c18d78d5e505 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -278,6 +278,7 @@ enum avic_ipi_failure_cause {
#define AVIC_HPA_MASK ~((0xFFFULL << 52) | 0xFFF)
#define VMCB_AVIC_APIC_BAR_MASK 0xFFFFFFFFFF000ULL

+#define SVM_SEV_FEAT_SNP_ACTIVE BIT(0)

struct vmcb_seg {
u16 selector;
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 51db01b282eb..a8efe1f6bf77 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -243,6 +243,25 @@ 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)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
@@ -256,13 +275,23 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
return ret;

sev->active = true;
- sev->es_active = argp->id == KVM_SEV_ES_INIT;
+ sev->es_active = (argp->id == KVM_SEV_ES_INIT || argp->id == KVM_SEV_SNP_INIT);
+ sev->snp_active = argp->id == KVM_SEV_SNP_INIT;
asid = sev_asid_new(sev);
if (asid < 0)
goto e_no_asid;
sev->asid = asid;

- ret = sev_platform_init(&argp->error);
+ if (sev->snp_active) {
+ ret = verify_snp_init_flags(kvm, argp);
+ if (ret)
+ goto e_free;
+
+ ret = sev_snp_init(&argp->error, false);
+ } else {
+ ret = sev_platform_init(&argp->error);
+ }
+
if (ret)
goto e_free;

@@ -277,6 +306,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
sev_asid_free(sev);
sev->asid = 0;
e_no_asid:
+ sev->snp_active = false;
sev->es_active = false;
sev->active = false;
return ret;
@@ -749,6 +779,10 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
save->xss = svm->vcpu.arch.ia32_xss;
save->dr6 = svm->vcpu.arch.dr6;

+ /* Enable the SEV-SNP feature */
+ if (sev_snp_guest(svm->vcpu.kvm))
+ save->sev_features |= SVM_SEV_FEAT_SNP_ACTIVE;
+
pr_debug("Virtual Machine Save Area (VMSA):\n");
print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, save, sizeof(*save), false);

@@ -2001,6 +2035,12 @@ int sev_mem_enc_ioctl(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 8eb1b51e92f5..56a5c96d8a36 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -73,6 +73,9 @@ 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 */
@@ -88,6 +91,7 @@ struct kvm_sev_info {
struct list_head mirror_entry; /* Use as a list entry of mirrors */
struct misc_cg *misc_cg; /* For misc cgroup accounting */
atomic_t migration_in_progress;
+ u64 snp_init_flags;
};

struct kvm_svm {
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 2fba29125ec2..499cc323f793 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1917,6 +1917,9 @@ enum sev_cmd_id {
/* Guest Migration Extension */
KVM_SEV_SEND_CANCEL,

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

@@ -2013,6 +2016,16 @@ 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)
--
2.25.1