diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 70d5650d8d95..18b64b7005e7 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2089,6 +2089,7 @@ static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		goto e_free;
 
 	sev->snp_certs_data = certs_data;
+	sev->snp_certs_len = 0;
 
 	return context;
 
@@ -2404,6 +2405,86 @@ static int snp_launch_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int snp_get_instance_certs(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct kvm_sev_snp_get_certs params;
+
+	if (!sev_snp_guest(kvm))
+		return -ENOTTY;
+
+	if (!sev->snp_context)
+		return -EINVAL;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
+			   sizeof(params)))
+		return -EFAULT;
+
+	/* No instance certs set. */
+	if (!sev->snp_certs_len)
+		return -ENOENT;
+
+	if (params.certs_len < sev->snp_certs_len) {
+		/* Output buffer too small. Return the required size. */
+		params.certs_len = sev->snp_certs_len;
+
+		if (copy_to_user((void __user *)(uintptr_t)argp->data, &params,
+				 sizeof(params)))
+			return -EFAULT;
+
+		return -EINVAL;
+	}
+
+	if (copy_to_user((void __user *)(uintptr_t)params.certs_uaddr,
+			 sev->snp_certs_data, sev->snp_certs_len))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int snp_set_instance_certs(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	unsigned long length = SEV_FW_BLOB_MAX_SIZE;
+	void *to_certs = sev->snp_certs_data;
+	struct kvm_sev_snp_set_certs params;
+
+	if (!sev_snp_guest(kvm))
+		return -ENOTTY;
+
+	if (!sev->snp_context)
+		return -EINVAL;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
+			   sizeof(params)))
+		return -EFAULT;
+
+	if (params.certs_len > SEV_FW_BLOB_MAX_SIZE)
+		return -EINVAL;
+
+	/*
+	 * Setting a length of 0 is the same as "uninstalling" instance-
+	 * specific certificates.
+	 */
+	if (params.certs_len == 0) {
+		sev->snp_certs_len = 0;
+		return 0;
+	}
+
+	/* Page-align the length */
+	length = (params.certs_len + PAGE_SIZE - 1) & PAGE_MASK;
+
+	if (copy_from_user(to_certs,
+			   (void __user *)(uintptr_t)params.certs_uaddr,
+			   params.certs_len)) {
+		return -EFAULT;
+	}
+
+	sev->snp_certs_len = length;
+
+	return 0;
+}
+
 int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -2503,6 +2584,12 @@ int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
 	case KVM_SEV_SNP_LAUNCH_FINISH:
 		r = snp_launch_finish(kvm, &sev_cmd);
 		break;
+	case KVM_SEV_SNP_GET_CERTS:
+		r = snp_get_instance_certs(kvm, &sev_cmd);
+		break;
+	case KVM_SEV_SNP_SET_CERTS:
+		r = snp_set_instance_certs(kvm, &sev_cmd);
+		break;
 	default:
 		r = -EINVAL;
 		goto out;
@@ -3550,8 +3637,28 @@ static void snp_handle_ext_guest_request(struct vcpu_svm *svm, gpa_t req_gpa, gp
 	if (rc)
 		goto unlock;
 
-	rc = snp_guest_ext_guest_request(&req, (unsigned long)sev->snp_certs_data,
-					 &data_npages, &err);
+	/*
+	 * If the VMM has overridden the certs, then change the error message
+	 * if the size is inappropriate for the override. Otherwise, use a
+	 * regular guest request and copy back the instance certs.
+	 */
+	if (sev->snp_certs_len) {
+		if ((data_npages << PAGE_SHIFT) < sev->snp_certs_len) {
+			rc = -EINVAL;
+			err = SNP_GUEST_REQ_INVALID_LEN;
+			goto datalen;
+		}
+		rc = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &req,
+				   (int *)&err);
+	} else {
+		rc = snp_guest_ext_guest_request(&req,
+						 (unsigned long)sev->snp_certs_data,
+						 &data_npages, &err);
+	}
+datalen:
+	if (sev->snp_certs_len)
+		data_npages = sev->snp_certs_len >> PAGE_SHIFT;
+
 	if (rc) {
 		/*
 		 * If buffer length is small then return the expected
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 221b38d3c845..dced46559508 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -94,6 +94,7 @@ struct kvm_sev_info {
 	u64 snp_init_flags;
 	void *snp_context;      /* SNP guest context page */
 	void *snp_certs_data;
+	unsigned int snp_certs_len; /* Size of instance override for certs */
 	struct mutex guest_req_lock; /* Lock for guest request handling */
 
 	u64 sev_features;	/* Features set at VMSA creation */
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 92116e2b74fd..3b28b78938f6 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -22,7 +22,7 @@
 #define __psp_pa(x)	__pa(x)
 #endif
 
-#define SEV_FW_BLOB_MAX_SIZE	0x4000	/* 16KB */
+#define SEV_FW_BLOB_MAX_SIZE	0x5000	/* 20KB */
 
 /**
  * SEV platform state
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6e684bf5f723..ad7e24e43547 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1928,6 +1928,8 @@ enum sev_cmd_id {
 	KVM_SEV_SNP_LAUNCH_START,
 	KVM_SEV_SNP_LAUNCH_UPDATE,
 	KVM_SEV_SNP_LAUNCH_FINISH,
+	KVM_SEV_SNP_GET_CERTS,
+	KVM_SEV_SNP_SET_CERTS,
 
 	KVM_SEV_NR_MAX,
 };
@@ -2075,6 +2077,16 @@ struct kvm_sev_snp_launch_finish {
 	__u8 pad[6];
 };
 
+struct kvm_sev_snp_get_certs {
+	__u64 certs_uaddr;
+	__u64 certs_len;
+};
+
+struct kvm_sev_snp_set_certs {
+	__u64 certs_uaddr;
+	__u64 certs_len;
+};
+
 #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)
