[PATCH Part2 v6 42/49] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event

Ashish Kalra
2022-06-20T23:17:58Z

From: Brijesh Singh <brijesh.singh@amd.com>

Version 2 of GHCB specification added the support for two SNP Guest
Request Message NAE events. The events allows for an SEV-SNP guest to
make request to the SEV-SNP firmware through hypervisor using the
SNP_GUEST_REQUEST API define in the SEV-SNP firmware specification.

The SNP_EXT_GUEST_REQUEST is similar to SNP_GUEST_REQUEST with the
difference of an additional certificate blob that can be passed through
the SNP_SET_CONFIG ioctl defined in the CCP driver. The CCP driver
provides snp_guest_ext_guest_request() that is used by the KVM to get
both the report and certificate data at once.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/kvm/svm/sev.c | 196 +++++++++++++++++++++++++++++++++++++++--
arch/x86/kvm/svm/svm.h | 2 +
2 files changed, 192 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 7fc0fad87054..089af21a4efe 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -343,6 +343,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)

spin_lock_init(&sev->psc_lock);
ret = sev_snp_init(&argp->error);
+ mutex_init(&sev->guest_req_lock);
} else {
ret = sev_platform_init(&argp->error);
}
@@ -1884,23 +1885,39 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)

static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
+ void *context = NULL, *certs_data = NULL, *resp_page = NULL;
+ struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
struct sev_data_snp_gctx_create data = {};
- void *context;
int rc;

+ /* Allocate memory used for the certs data in SNP guest request */
+ certs_data = kmalloc(SEV_FW_BLOB_MAX_SIZE, GFP_KERNEL_ACCOUNT);
+ if (!certs_data)
+ return NULL;
+
/* Allocate memory for context page */
context = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);
if (!context)
- return NULL;
+ goto e_free;
+
+ /* Allocate a firmware buffer used during the guest command handling. */
+ resp_page = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);
+ if (!resp_page)
+ goto e_free;

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;
- }
+ if (rc)
+ goto e_free;
+
+ sev->snp_certs_data = certs_data;

return context;
+
+e_free:
+ snp_free_firmware_page(context);
+ kfree(certs_data);
+ return NULL;
}

static int snp_bind_asid(struct kvm *kvm, int *error)
@@ -2565,6 +2582,8 @@ static int snp_decommission_context(struct kvm *kvm)
snp_free_firmware_page(sev->snp_context);
sev->snp_context = NULL;

+ kfree(sev->snp_certs_data);
+
return 0;
}

@@ -3077,6 +3096,8 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm, u64 *exit_code)
case SVM_VMGEXIT_UNSUPPORTED_EVENT:
case SVM_VMGEXIT_HV_FEATURES:
case SVM_VMGEXIT_PSC:
+ case SVM_VMGEXIT_GUEST_REQUEST:
+ case SVM_VMGEXIT_EXT_GUEST_REQUEST:
break;
default:
reason = GHCB_ERR_INVALID_EVENT;
@@ -3502,6 +3523,155 @@ static unsigned long snp_handle_page_state_change(struct vcpu_svm *svm)
return rc ? map_to_psc_vmgexit_code(rc) : 0;
}

+static unsigned long snp_setup_guest_buf(struct vcpu_svm *svm,
+ struct sev_data_snp_guest_request *data,
+ gpa_t req_gpa, gpa_t resp_gpa)
+{
+ struct kvm_vcpu *vcpu = &svm->vcpu;
+ struct kvm *kvm = vcpu->kvm;
+ kvm_pfn_t req_pfn, resp_pfn;
+ struct kvm_sev_info *sev;
+
+ sev = &to_kvm_svm(kvm)->sev_info;
+
+ if (!IS_ALIGNED(req_gpa, PAGE_SIZE) || !IS_ALIGNED(resp_gpa, PAGE_SIZE))
+ return SEV_RET_INVALID_PARAM;
+
+ req_pfn = gfn_to_pfn(kvm, gpa_to_gfn(req_gpa));
+ if (is_error_noslot_pfn(req_pfn))
+ return SEV_RET_INVALID_ADDRESS;
+
+ resp_pfn = gfn_to_pfn(kvm, gpa_to_gfn(resp_gpa));
+ if (is_error_noslot_pfn(resp_pfn))
+ return SEV_RET_INVALID_ADDRESS;
+
+ if (rmp_make_private(resp_pfn, 0, PG_LEVEL_4K, 0, true))
+ return SEV_RET_INVALID_ADDRESS;
+
+ data->gctx_paddr = __psp_pa(sev->snp_context);
+ data->req_paddr = __sme_set(req_pfn << PAGE_SHIFT);
+ data->res_paddr = __sme_set(resp_pfn << PAGE_SHIFT);
+
+ return 0;
+}
+
+static void snp_cleanup_guest_buf(struct sev_data_snp_guest_request *data, unsigned long *rc)
+{
+ u64 pfn = __sme_clr(data->res_paddr) >> PAGE_SHIFT;
+ int ret;
+
+ ret = snp_page_reclaim(pfn);
+ if (ret)
+ *rc = SEV_RET_INVALID_ADDRESS;
+
+ ret = rmp_make_shared(pfn, PG_LEVEL_4K);
+ if (ret)
+ *rc = SEV_RET_INVALID_ADDRESS;
+}
+
+static void snp_handle_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa)
+{
+ struct sev_data_snp_guest_request data = {0};
+ struct kvm_vcpu *vcpu = &svm->vcpu;
+ struct kvm *kvm = vcpu->kvm;
+ struct kvm_sev_info *sev;
+ unsigned long rc;
+ int err;
+
+ if (!sev_snp_guest(vcpu->kvm)) {
+ rc = SEV_RET_INVALID_GUEST;
+ goto e_fail;
+ }
+
+ sev = &to_kvm_svm(kvm)->sev_info;
+
+ mutex_lock(&sev->guest_req_lock);
+
+ rc = snp_setup_guest_buf(svm, &data, req_gpa, resp_gpa);
+ if (rc)
+ goto unlock;
+
+ rc = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, &err);
+ if (rc)
+ /* use the firmware error code */
+ rc = err;
+
+ snp_cleanup_guest_buf(&data, &rc);
+
+unlock:
+ mutex_unlock(&sev->guest_req_lock);
+
+e_fail:
+ svm_set_ghcb_sw_exit_info_2(vcpu, rc);
+}
+
+static void snp_handle_ext_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t resp_gpa)
+{
+ struct sev_data_snp_guest_request req = {0};
+ struct kvm_vcpu *vcpu = &svm->vcpu;
+ struct kvm *kvm = vcpu->kvm;
+ unsigned long data_npages;
+ struct kvm_sev_info *sev;
+ unsigned long rc, err;
+ u64 data_gpa;
+
+ if (!sev_snp_guest(vcpu->kvm)) {
+ rc = SEV_RET_INVALID_GUEST;
+ goto e_fail;
+ }
+
+ sev = &to_kvm_svm(kvm)->sev_info;
+
+ data_gpa = vcpu->arch.regs[VCPU_REGS_RAX];
+ data_npages = vcpu->arch.regs[VCPU_REGS_RBX];
+
+ if (!IS_ALIGNED(data_gpa, PAGE_SIZE)) {
+ rc = SEV_RET_INVALID_ADDRESS;
+ goto e_fail;
+ }
+
+ /* Verify that requested blob will fit in certificate buffer */
+ if ((data_npages << PAGE_SHIFT) > SEV_FW_BLOB_MAX_SIZE) {
+ rc = SEV_RET_INVALID_PARAM;
+ goto e_fail;
+ }
+
+ mutex_lock(&sev->guest_req_lock);
+
+ rc = snp_setup_guest_buf(svm, &req, req_gpa, resp_gpa);
+ if (rc)
+ goto unlock;
+
+ rc = snp_guest_ext_guest_request(&req, (unsigned long)sev->snp_certs_data,
+ &data_npages, &err);
+ if (rc) {
+ /*
+ * If buffer length is small then return the expected
+ * length in rbx.
+ */
+ if (err == SNP_GUEST_REQ_INVALID_LEN)
+ vcpu->arch.regs[VCPU_REGS_RBX] = data_npages;
+
+ /* pass the firmware error code */
+ rc = err;
+ goto cleanup;
+ }
+
+ /* Copy the certificate blob in the guest memory */
+ if (data_npages &&
+ kvm_write_guest(kvm, data_gpa, sev->snp_certs_data, data_npages << PAGE_SHIFT))
+ rc = SEV_RET_INVALID_ADDRESS;
+
+cleanup:
+ snp_cleanup_guest_buf(&req, &rc);
+
+unlock:
+ mutex_unlock(&sev->guest_req_lock);
+
+e_fail:
+ svm_set_ghcb_sw_exit_info_2(vcpu, rc);
+}
+
static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
{
struct vmcb_control_area *control = &svm->vmcb->control;
@@ -3753,6 +3923,20 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
svm_set_ghcb_sw_exit_info_2(vcpu, rc);
break;
}
+ case SVM_VMGEXIT_GUEST_REQUEST: {
+ snp_handle_guest_request(svm, control->exit_info_1, control->exit_info_2);
+
+ ret = 1;
+ break;
+ }
+ case SVM_VMGEXIT_EXT_GUEST_REQUEST: {
+ snp_handle_ext_guest_request(svm,
+ control->exit_info_1,
+ control->exit_info_2);
+
+ ret = 1;
+ break;
+ }
case SVM_VMGEXIT_UNSUPPORTED_EVENT:
vcpu_unimpl(vcpu,
"vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 3fd95193ed8d..3be24da1a743 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -98,6 +98,8 @@ struct kvm_sev_info {
u64 snp_init_flags;
void *snp_context; /* SNP guest context page */
spinlock_t psc_lock;
+ void *snp_certs_data;
+ struct mutex guest_req_lock;
};

struct kvm_svm {
--
2.25.1