[PATCH Part2 RFC v3 20/37] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command

Brijesh Singh
2021-06-02T14:13:10Z

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>
---
arch/x86/kvm/svm/sev.c | 132 ++++++++++++++++++++++++++++++++++++++-
arch/x86/kvm/svm/svm.h | 1 +
include/uapi/linux/kvm.h | 9 +++
3 files changed, 141 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0cd0078baf75..dac71bdedac4 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -20,6 +20,7 @@
#include <asm/fpu/internal.h>

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

#include "x86.h"
#include "svm.h"
@@ -75,6 +76,8 @@ 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;
@@ -1508,6 +1511,100 @@ 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 = {};
+ int asid = sev_get_asid(kvm);
+ int ret, retry_count = 0;
+
+ /* Activate ASID on the given context */
+ data.gctx_paddr = __psp_pa(sev->snp_context);
+ data.asid = asid;
+again:
+ ret = sev_issue_cmd(kvm, SEV_CMD_SNP_ACTIVATE, &data, error);
+
+ /* Check if the DF_FLUSH is required, and try again */
+ if (ret && (*error == SEV_RET_DFFLUSH_REQUIRED) && (!retry_count)) {
+ /* Guard DEACTIVATE against WBINVD/DF_FLUSH used in ASID recycling */
+ down_read(&sev_deactivate_lock);
+ wbinvd_on_all_cpus();
+ ret = snp_guest_df_flush(error);
+ up_read(&sev_deactivate_lock);
+
+ if (ret)
+ return ret;
+
+ /* only one retry */
+ retry_count = 1;
+
+ goto again;
+ }
+
+ return ret;
+}
+
+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 = {};
+ 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;
+
+ /* Initialize the guest context */
+ sev->snp_context = snp_context_create(kvm, argp);
+ if (!sev->snp_context)
+ return -ENOTTY;
+
+ /* Issue the LAUNCH_START command */
+ 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;
+
+ /* Bind ASID to this guest */
+ 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;
@@ -1597,6 +1694,9 @@ 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;
@@ -1790,6 +1890,28 @@ 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 (ret)
+ 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;
@@ -1828,7 +1950,15 @@ 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)) {
+ pr_err("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 b9ea99f8579e..bc5582b44356 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -67,6 +67,7 @@ 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 */
+ 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 f3a86d3a8f04..56ab5576741e 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1680,6 +1680,7 @@ enum sev_cmd_id {

/* SNP specific commands */
KVM_SEV_SNP_INIT = 255,
+ KVM_SEV_SNP_LAUNCH_START,

KVM_SEV_NR_MAX,
};
@@ -1777,6 +1778,14 @@ struct kvm_sev_receive_update_data {
__u32 trans_len;
};

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