[PATCH RFC v9 50/51] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event

Michael Roth
2023-06-12T04:58:16Z

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.

Co-developed-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
[mdr: ensure FW command failures are indicated to guest]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
arch/x86/kvm/svm/sev.c | 175 +++++++++++++++++++++++++++++++++++
arch/x86/kvm/svm/svm.h | 1 +
drivers/crypto/ccp/sev-dev.c | 15 +++
include/linux/psp-sev.h | 1 +
4 files changed, 192 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index bdf32aa971d8..9f7defce1988 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -328,6 +328,8 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
ret = verify_snp_init_flags(kvm, argp);
if (ret)
goto e_free;
+
+ mutex_init(&sev->guest_req_lock);
}

ret = sev_platform_init(&argp->error);
@@ -2321,8 +2323,10 @@ static int snp_get_instance_certs(struct kvm *kvm, struct kvm_sev_cmd *argp)

static void snp_replace_certs(struct kvm_sev_info *sev, struct sev_snp_certs *snp_certs)
{
+ mutex_lock(&sev->guest_req_lock);
sev_snp_certs_put(sev->snp_certs);
sev->snp_certs = snp_certs;
+ mutex_unlock(&sev->guest_req_lock);
}

static int snp_set_instance_certs(struct kvm *kvm, struct kvm_sev_cmd *argp)
@@ -3171,6 +3175,8 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
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;
@@ -3604,6 +3610,163 @@ static int sev_snp_ap_creation(struct vcpu_svm *svm)
return ret;
}

+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)
+ /* Ensure an error value is returned to guest. */
+ rc = err ? err : SEV_RET_INVALID_ADDRESS;
+
+ snp_cleanup_guest_buf(&data, &rc);
+
+unlock:
+ mutex_unlock(&sev->guest_req_lock);
+
+e_fail:
+ ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, 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 sev_snp_certs *snp_certs = NULL;
+ struct kvm_vcpu *vcpu = &svm->vcpu;
+ struct kvm *kvm = vcpu->kvm;
+ unsigned long data_npages;
+ struct kvm_sev_info *sev;
+ unsigned long exitcode = 0;
+ u64 data_gpa;
+ int err, rc;
+
+ 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)) {
+ exitcode = SEV_RET_INVALID_ADDRESS;
+ goto e_fail;
+ }
+
+ mutex_lock(&sev->guest_req_lock);
+
+ rc = snp_setup_guest_buf(svm, &req, req_gpa, resp_gpa);
+ if (rc)
+ goto unlock;
+
+ /*
+ * If a VMM-specific certificate blob hasn't been provided, grab the
+ * host-wide one.
+ */
+ snp_certs = sev_snp_certs_get(sev->snp_certs);
+ if (!snp_certs)
+ snp_certs = sev_snp_global_certs_get();
+
+ /*
+ * If there is a host-wide or VMM-specific certificate blob available,
+ * make sure the guest has allocated enough space to store it.
+ * Otherwise, inform the guest how much space is needed.
+ */
+ if (snp_certs && (data_npages << PAGE_SHIFT) < snp_certs->len) {
+ vcpu->arch.regs[VCPU_REGS_RBX] = snp_certs->len >> PAGE_SHIFT;
+ exitcode = SNP_GUEST_REQ_INVALID_LEN;
+ goto cleanup;
+ }
+
+ rc = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &req, &err);
+ if (rc) {
+ /* pass the firmware error code */
+ exitcode = err;
+ goto cleanup;
+ }
+
+ /* Copy the certificate blob in the guest memory */
+ if (sev->snp_certs &&
+ kvm_write_guest(kvm, data_gpa, sev->snp_certs->data, sev->snp_certs->len))
+ exitcode = SEV_RET_INVALID_ADDRESS;
+
+cleanup:
+ sev_snp_certs_put(snp_certs);
+ snp_cleanup_guest_buf(&req, &exitcode);
+
+unlock:
+ mutex_unlock(&sev->guest_req_lock);
+
+e_fail:
+ ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, exitcode);
+}
+
static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
{
struct vmcb_control_area *control = &svm->vmcb->control;
@@ -3863,6 +4026,18 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
SVM_EVTINJ_VALID);
}

+ ret = 1;
+ 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:
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 72be0c440b16..31cd8b3e6877 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -96,6 +96,7 @@ struct kvm_sev_info {
void *snp_context; /* SNP guest context page */
u64 sev_features; /* Features set at VMSA creation */
struct sev_snp_certs *snp_certs;
+ struct mutex guest_req_lock; /* Lock for guest request handling */
};

struct kvm_svm {
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 175c24163ba0..096ba15d0740 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -2109,6 +2109,21 @@ void sev_snp_certs_put(struct sev_snp_certs *certs)
}
EXPORT_SYMBOL_GPL(sev_snp_certs_put);

+struct sev_snp_certs *sev_snp_global_certs_get(void)
+{
+ struct sev_device *sev;
+
+ if (!psp_master || !psp_master->sev_data)
+ return NULL;
+
+ sev = psp_master->sev_data;
+ if (!sev->snp_initialized)
+ return NULL;
+
+ return sev_snp_certs_get(sev->snp_certs);
+}
+EXPORT_SYMBOL_GPL(sev_snp_global_certs_get);
+
static void sev_exit(struct kref *ref)
{
misc_deregister(&misc_dev->misc);
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 7b65dd5808a1..1235eb3110cb 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -33,6 +33,7 @@ struct sev_snp_certs {
struct sev_snp_certs *sev_snp_certs_new(void *data, u32 len);
struct sev_snp_certs *sev_snp_certs_get(struct sev_snp_certs *certs);
void sev_snp_certs_put(struct sev_snp_certs *certs);
+struct sev_snp_certs *sev_snp_global_certs_get(void);

/**
* SEV platform state
--
2.25.1