Date:   Mon, 20 Jun 2022 23:13:18 +0000
From:   Ashish Kalra <Ashish.Kalra@....com>
To:     <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <kvm@...r.kernel.org>, <linux-coco@...ts.linux.dev>,
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Subject: [PATCH Part2 v6 42/49] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event

From: Brijesh Singh <brijesh.singh@....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@....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

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