[PATCH Part2 v5 24/45] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command

Brijesh Singh
2021-08-20T16:00:30Z

KVM_SEV_SNP_LAUNCH_START begins the launch process for an SEV-SNP guest.
The command initializes a cryptographic digest context used to construct
the measurement of the guest. If the guest is expected to be migrated,
the command also binds a migration agent (MA) to the guest.

For more information see the SEV-SNP specification.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
.../virt/kvm/amd-memory-encryption.rst | 24 ++++
arch/x86/kvm/svm/sev.c | 116 +++++++++++++++++-
arch/x86/kvm/svm/svm.h | 1 +
include/uapi/linux/kvm.h | 10 ++
4 files changed, 148 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index 7b1d32fb99a8..937af3447954 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst
@@ -454,6 +454,30 @@ The flags bitmap is defined as::
If the specified flags is not supported then return -EOPNOTSUPP, and the supported
flags are returned.

+19. KVM_SNP_LAUNCH_START
+------------------------
+
+The KVM_SNP_LAUNCH_START command is used for creating the memory encryption
+context for the SEV-SNP guest. To create the encryption context, user must
+provide a guest policy, migration agent (if any) and guest OS visible
+workarounds value as defined SEV-SNP specification.
+
+Parameters (in): struct kvm_snp_launch_start
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_snp_launch_start {
+ __u64 policy; /* Guest policy to use. */
+ __u64 ma_uaddr; /* userspace address of migration agent */
+ __u8 ma_en; /* 1 if the migtation agent is enabled */
+ __u8 imi_en; /* set IMI to 1. */
+ __u8 gosvw[16]; /* guest OS visible workarounds */
+ };
+
+See the SEV-SNP specification for further detail on the launch input.
+
References
==========

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 93da463545ef..dbf04a52b23d 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -21,6 +21,7 @@

#include <asm/pkru.h>
#include <asm/trapnr.h>
+#include <asm/sev.h>

#include "x86.h"
#include "svm.h"
@@ -74,6 +75,8 @@ static unsigned long sev_me_mask;
static unsigned long *sev_asid_bitmap;
static unsigned long *sev_reclaim_asid_bitmap;

+static int snp_decommission_context(struct kvm *kvm);
+
struct enc_region {
struct list_head list;
unsigned long npages;
@@ -85,7 +88,7 @@ struct enc_region {
/* Called with the sev_bitmap_lock held, or on shutdown */
static int sev_flush_asids(int min_asid, int max_asid)
{
- int ret, pos, error = 0;
+ int ret, pos, error = 0, ret_snp = 0, error_snp = 0;

/* Check if there are any ASIDs to reclaim before performing a flush */
pos = find_next_bit(sev_reclaim_asid_bitmap, max_asid, min_asid);
@@ -101,12 +104,18 @@ static int sev_flush_asids(int min_asid, int max_asid)
wbinvd_on_all_cpus();
ret = sev_guest_df_flush(&error);

+ if (sev_snp_enabled)
+ ret_snp = snp_guest_df_flush(&error_snp);
+
up_write(&sev_deactivate_lock);

if (ret)
pr_err("SEV: DF_FLUSH failed, ret=%d, error=%#x\n", ret, error);

- return ret;
+ if (ret_snp)
+ pr_err("SEV: SNP_DF_FLUSH failed, ret=%d, error=%#x\n", ret_snp, error_snp);
+
+ return ret || ret_snp;
}

static inline bool is_mirroring_enc_context(struct kvm *kvm)
@@ -1543,6 +1552,74 @@ static int sev_receive_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
return sev_issue_cmd(kvm, SEV_CMD_RECEIVE_FINISH, &data, &argp->error);
}

+static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+ struct sev_data_snp_gctx_create data = {};
+ void *context;
+ int rc;
+
+ /* Allocate memory for context page */
+ context = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);
+ if (!context)
+ return NULL;
+
+ data.gctx_paddr = __psp_pa(context);
+ rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_GCTX_CREATE, &data, &argp->error);
+ if (rc) {
+ snp_free_firmware_page(context);
+ return NULL;
+ }
+
+ return context;
+}
+
+static int snp_bind_asid(struct kvm *kvm, int *error)
+{
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ struct sev_data_snp_activate data = {0};
+
+ data.gctx_paddr = __psp_pa(sev->snp_context);
+ data.asid = sev_get_asid(kvm);
+ return sev_issue_cmd(kvm, SEV_CMD_SNP_ACTIVATE, &data, error);
+}
+
+static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ struct sev_data_snp_launch_start start = {0};
+ struct kvm_sev_snp_launch_start params;
+ int rc;
+
+ if (!sev_snp_guest(kvm))
+ return -ENOTTY;
+
+ if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+ return -EFAULT;
+
+ sev->snp_context = snp_context_create(kvm, argp);
+ if (!sev->snp_context)
+ return -ENOTTY;
+
+ start.gctx_paddr = __psp_pa(sev->snp_context);
+ start.policy = params.policy;
+ memcpy(start.gosvw, params.gosvw, sizeof(params.gosvw));
+ rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_START, &start, &argp->error);
+ if (rc)
+ goto e_free_context;
+
+ sev->fd = argp->sev_fd;
+ rc = snp_bind_asid(kvm, &argp->error);
+ if (rc)
+ goto e_free_context;
+
+ return 0;
+
+e_free_context:
+ snp_decommission_context(kvm);
+
+ return rc;
+}
+
int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -1632,6 +1709,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
case KVM_SEV_RECEIVE_FINISH:
r = sev_receive_finish(kvm, &sev_cmd);
break;
+ case KVM_SEV_SNP_LAUNCH_START:
+ r = snp_launch_start(kvm, &sev_cmd);
+ break;
default:
r = -EINVAL;
goto out;
@@ -1825,6 +1905,28 @@ int svm_vm_copy_asid_from(struct kvm *kvm, unsigned int source_fd)
return ret;
}

+static int snp_decommission_context(struct kvm *kvm)
+{
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+ struct sev_data_snp_decommission data = {};
+ int ret;
+
+ /* If context is not created then do nothing */
+ if (!sev->snp_context)
+ return 0;
+
+ data.gctx_paddr = __sme_pa(sev->snp_context);
+ ret = snp_guest_decommission(&data, NULL);
+ if (WARN_ONCE(ret, "failed to release guest context"))
+ return ret;
+
+ /* free the context page now */
+ snp_free_firmware_page(sev->snp_context);
+ sev->snp_context = NULL;
+
+ return 0;
+}
+
void sev_vm_destroy(struct kvm *kvm)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
@@ -1863,7 +1965,15 @@ void sev_vm_destroy(struct kvm *kvm)

mutex_unlock(&kvm->lock);

- sev_unbind_asid(kvm, sev->handle);
+ if (sev_snp_guest(kvm)) {
+ if (snp_decommission_context(kvm)) {
+ WARN_ONCE(1, "Failed to free SNP guest context, leaking asid!\n");
+ return;
+ }
+ } else {
+ sev_unbind_asid(kvm, sev->handle);
+ }
+
sev_asid_free(sev);
}

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 57c3c404b0b3..85417c44812d 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -85,6 +85,7 @@ struct kvm_sev_info {
struct kvm *enc_context_owner; /* Owner of copied encryption context */
struct misc_cg *misc_cg; /* For misc cgroup accounting */
u64 snp_init_flags;
+ void *snp_context; /* SNP guest context page */
};

struct kvm_svm {
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 944e2bf601fe..e6416e58cd9a 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1714,6 +1714,7 @@ enum sev_cmd_id {

/* SNP specific commands */
KVM_SEV_SNP_INIT,
+ KVM_SEV_SNP_LAUNCH_START,

KVM_SEV_NR_MAX,
};
@@ -1821,6 +1822,15 @@ struct kvm_snp_init {
__u64 flags;
};

+struct kvm_sev_snp_launch_start {
+ __u64 policy;
+ __u64 ma_uaddr;
+ __u8 ma_en;
+ __u8 imi_en;
+ __u8 gosvw[16];
+ __u8 pad[6];
+};
+
#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