KVM: SEV: Add KVM_SEV_SNP_LAUNCH_START command

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. Other commands can then at that point be
used to load/encrypt data into the guest's initial launch image.

For more information see the SEV-SNP specification.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Co-developed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Message-ID: <20240501085210.2213060-6-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
index 9677a0714a39d0ab9c8e6d1543e6477a9ad6e0fc..dd179e162a8794c0bc273bbf30504dd9e72f38fb 100644 (file)
--- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
@@ -466,6 +466,30 @@ issued by the hypervisor to make the guest ready for execution.
 
 Returns: 0 on success, -negative on error
 
+18. KVM_SEV_SNP_LAUNCH_START
+----------------------------
+
+The KVM_SNP_LAUNCH_START command is used for creating the memory encryption
+context for the SEV-SNP guest. It must be called prior to issuing
+KVM_SEV_SNP_LAUNCH_UPDATE or KVM_SEV_SNP_LAUNCH_FINISH;
+
+Parameters (in): struct  kvm_sev_snp_launch_start
+
+Returns: 0 on success, -negative on error
+
+::
+
+        struct kvm_sev_snp_launch_start {
+                __u64 policy;           /* Guest policy to use. */
+                __u8 gosvw[16];         /* Guest OS visible workarounds. */
+                __u16 flags;            /* Must be zero. */
+                __u8 pad0[6];
+                __u64 pad1[4];
+        };
+
+See SNP_LAUNCH_START in the SEV-SNP specification [snp-fw-abi]_ for further
+details on the input parameters in ``struct kvm_sev_snp_launch_start``.
+
 Device attribute API
 ====================
 
@@ -497,9 +521,11 @@ References
 ==========
 
 
-See [white-paper]_, [api-spec]_, [amd-apm]_ and [kvm-forum]_ for more info.
+See [white-paper]_, [api-spec]_, [amd-apm]_, [kvm-forum]_, and [snp-fw-abi]_
+for more info.
 
 .. [white-paper] https://developer.amd.com/wordpress/media/2013/12/AMD_Memory_Encryption_Whitepaper_v7-Public.pdf
 .. [api-spec] https://support.amd.com/TechDocs/55766_SEV-KM_API_Specification.pdf
 .. [amd-apm] https://support.amd.com/TechDocs/24593.pdf (section 15.34)
 .. [kvm-forum]  https://www.linux-kvm.org/images/7/74/02x08A-Thomas_Lendacky-AMDs_Virtualizatoin_Memory_Encryption_Technology.pdf
+.. [snp-fw-abi] https://www.amd.com/system/files/TechDocs/56860.pdf

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index d2ae5fcc02759813a3a2f9981c3afd437b92f24a..693a80ffe40a4b14facc2bbdc7e0039dd48fbeac 100644 (file)
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -697,6 +697,9 @@ enum sev_cmd_id {
        /* Second time is the charm; improved versions of the above ioctls.  */
        KVM_SEV_INIT2,
 
+       /* SNP-specific commands */
+       KVM_SEV_SNP_LAUNCH_START = 100,
+
        KVM_SEV_NR_MAX,
 };
 
@@ -824,6 +827,14 @@ struct kvm_sev_receive_update_data {
        __u32 pad2;
 };
 
+struct kvm_sev_snp_launch_start {
+       __u64 policy;
+       __u8 gosvw[16];
+       __u16 flags;
+       __u8 pad0[6];
+       __u64 pad1[4];
+};
+
 #define KVM_X2APIC_API_USE_32BIT_IDS            (1ULL << 0)
 #define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK  (1ULL << 1)
 

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index b3345d45b989ad08803864ce768eadef97ae24c4..b372ae5c8c585d683e9e347fba9b0c7e97c72116 100644 (file)
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -25,6 +25,7 @@
 #include <asm/fpu/xcr.h>
 #include <asm/fpu/xstate.h>
 #include <asm/debugreg.h>
+#include <asm/sev.h>
 
 #include "mmu.h"
 #include "x86.h"
@@ -59,6 +60,21 @@ static u64 sev_supported_vmsa_features;
 #define AP_RESET_HOLD_NAE_EVENT                1
 #define AP_RESET_HOLD_MSR_PROTO                2
 
+/* As defined by SEV-SNP Firmware ABI, under "Guest Policy". */
+#define SNP_POLICY_MASK_API_MINOR      GENMASK_ULL(7, 0)
+#define SNP_POLICY_MASK_API_MAJOR      GENMASK_ULL(15, 8)
+#define SNP_POLICY_MASK_SMT            BIT_ULL(16)
+#define SNP_POLICY_MASK_RSVD_MBO       BIT_ULL(17)
+#define SNP_POLICY_MASK_DEBUG          BIT_ULL(19)
+#define SNP_POLICY_MASK_SINGLE_SOCKET  BIT_ULL(20)
+
+#define SNP_POLICY_MASK_VALID          (SNP_POLICY_MASK_API_MINOR      | \
+                                        SNP_POLICY_MASK_API_MAJOR      | \
+                                        SNP_POLICY_MASK_SMT            | \
+                                        SNP_POLICY_MASK_RSVD_MBO       | \
+                                        SNP_POLICY_MASK_DEBUG          | \
+                                        SNP_POLICY_MASK_SINGLE_SOCKET)
+
 static u8 sev_enc_bit;
 static DECLARE_RWSEM(sev_deactivate_lock);
 static DEFINE_MUTEX(sev_bitmap_lock);
@@ -69,6 +85,8 @@ static unsigned int nr_asids;
 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;
@@ -95,12 +113,17 @@ static int sev_flush_asids(unsigned int min_asid, unsigned int max_asid)
        down_write(&sev_deactivate_lock);
 
        wbinvd_on_all_cpus();
-       ret = sev_guest_df_flush(&error);
+
+       if (sev_snp_enabled)
+               ret = sev_do_cmd(SEV_CMD_SNP_DF_FLUSH, NULL, &error);
+       else
+               ret = sev_guest_df_flush(&error);
 
        up_write(&sev_deactivate_lock);
 
        if (ret)
-               pr_err("SEV: DF_FLUSH failed, ret=%d, error=%#x\n", ret, error);
+               pr_err("SEV%s: DF_FLUSH failed, ret=%d, error=%#x\n",
+                      sev_snp_enabled ? "-SNP" : "", ret, error);
 
        return ret;
 }
@@ -1998,6 +2021,106 @@ int sev_dev_get_attr(u32 group, u64 attr, u64 *val)
        }
 }
 
+/*
+ * The guest context contains all the information, keys and metadata
+ * associated with the guest that the firmware tracks to implement SEV
+ * and SNP features. The firmware stores the guest context in hypervisor
+ * provide page via the SNP_GCTX_CREATE command.
+ */
+static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+       struct sev_data_snp_addr data = {};
+       void *context;
+       int rc;
+
+       /* Allocate memory for context page */
+       context = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);
+       if (!context)
+               return NULL;
+
+       data.address = __psp_pa(context);
+       rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_GCTX_CREATE, &data, &argp->error);
+       if (rc) {
+               pr_warn("Failed to create SEV-SNP context, rc %d fw_error %d",
+                       rc, argp->error);
+               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, u64_to_user_ptr(argp->data), sizeof(params)))
+               return -EFAULT;
+
+       /* Don't allow userspace to allocate memory for more than 1 SNP context. */
+       if (sev->snp_context)
+               return -EINVAL;
+
+       sev->snp_context = snp_context_create(kvm, argp);
+       if (!sev->snp_context)
+               return -ENOTTY;
+
+       if (params.flags)
+               return -EINVAL;
+
+       if (params.policy & ~SNP_POLICY_MASK_VALID)
+               return -EINVAL;
+
+       /* Check for policy bits that must be set */
+       if (!(params.policy & SNP_POLICY_MASK_RSVD_MBO) ||
+           !(params.policy & SNP_POLICY_MASK_SMT))
+               return -EINVAL;
+
+       if (params.policy & SNP_POLICY_MASK_SINGLE_SOCKET)
+               return -EINVAL;
+
+       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) {
+               pr_debug("%s: SEV_CMD_SNP_LAUNCH_START firmware command failed, rc %d\n",
+                        __func__, rc);
+               goto e_free_context;
+       }
+
+       sev->fd = argp->sev_fd;
+       rc = snp_bind_asid(kvm, &argp->error);
+       if (rc) {
+               pr_debug("%s: Failed to bind ASID to SEV-SNP context, rc %d\n",
+                        __func__, rc);
+               goto e_free_context;
+       }
+
+       return 0;
+
+e_free_context:
+       snp_decommission_context(kvm);
+
+       return rc;
+}
+
 int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
 {
        struct kvm_sev_cmd sev_cmd;
@@ -2021,6 +2144,15 @@ int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
                goto out;
        }
 
+       /*
+        * Once KVM_SEV_INIT2 initializes a KVM instance as an SNP guest, only
+        * allow the use of SNP-specific commands.
+        */
+       if (sev_snp_guest(kvm) && sev_cmd.id < KVM_SEV_SNP_LAUNCH_START) {
+               r = -EPERM;
+               goto out;
+       }
+
        switch (sev_cmd.id) {
        case KVM_SEV_ES_INIT:
                if (!sev_es_enabled) {
@@ -2085,6 +2217,9 @@ int sev_mem_enc_ioctl(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;
@@ -2280,6 +2415,31 @@ e_source_fput:
        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_addr data = {};
+       int ret;
+
+       /* If context is not created then do nothing */
+       if (!sev->snp_context)
+               return 0;
+
+       /* Do the decommision, which will unbind the ASID from the SNP context */
+       data.address = __sme_pa(sev->snp_context);
+       down_write(&sev_deactivate_lock);
+       ret = sev_do_cmd(SEV_CMD_SNP_DECOMMISSION, &data, NULL);
+       up_write(&sev_deactivate_lock);
+
+       if (WARN_ONCE(ret, "Failed to release guest context, ret %d", ret))
+               return ret;
+
+       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;
@@ -2321,7 +2481,17 @@ void sev_vm_destroy(struct kvm *kvm)
                }
        }
 
-       sev_unbind_asid(kvm, sev->handle);
+       if (sev_snp_guest(kvm)) {
+               /*
+                * Decomission handles unbinding of the ASID. If it fails for
+                * some unexpected reason, just leak the ASID.
+                */
+               if (snp_decommission_context(kvm))
+                       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 583e035d38f80d1339fd340029d2397defdf894a..305772d36490c6849a223309d964950c1c8d27e5 100644 (file)
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -93,6 +93,7 @@ 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;
+       void *snp_context;      /* SNP guest context page */
 };
 
 struct kvm_svm {