virt: sev-guest: Consolidate SNP guest messaging parameters to a struct

Add a snp_guest_req structure to eliminate the need to pass a long list of
parameters. This structure will be used to call the SNP Guest message
request API, simplifying the function arguments.

Update the snp_issue_guest_request() prototype to include the new guest
request structure.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20241009092850.197575-5-nikunj@amd.com

1 files changed, 54 insertions, 30 deletions

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index a33daff516ed..2a1b542168b1 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -177,7 +177,7 @@ static struct aesgcm_ctx *snp_init_crypto(u8 *key, size_t keylen)
 	return ctx;
 }
 
-static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
+static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_req *req)
 {
 	struct snp_guest_msg *resp_msg = &snp_dev->secret_response;
 	struct snp_guest_msg *req_msg = &snp_dev->secret_request;
@@ -206,20 +206,19 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload,
 	 * If the message size is greater than our buffer length then return
 	 * an error.
 	 */
-	if (unlikely((resp_msg_hdr->msg_sz + ctx->authsize) > sz))
+	if (unlikely((resp_msg_hdr->msg_sz + ctx->authsize) > req->resp_sz))
 		return -EBADMSG;
 
 	/* Decrypt the payload */
 	memcpy(iv, &resp_msg_hdr->msg_seqno, min(sizeof(iv), sizeof(resp_msg_hdr->msg_seqno)));
-	if (!aesgcm_decrypt(ctx, payload, resp_msg->payload, resp_msg_hdr->msg_sz,
+	if (!aesgcm_decrypt(ctx, req->resp_buf, resp_msg->payload, resp_msg_hdr->msg_sz,
 			    &resp_msg_hdr->algo, AAD_LEN, iv, resp_msg_hdr->authtag))
 		return -EBADMSG;
 
 	return 0;
 }
 
-static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
-			void *payload, size_t sz)
+static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, struct snp_guest_req *req)
 {
 	struct snp_guest_msg *msg = &snp_dev->secret_request;
 	struct snp_guest_msg_hdr *hdr = &msg->hdr;
@@ -231,11 +230,11 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
 	hdr->algo = SNP_AEAD_AES_256_GCM;
 	hdr->hdr_version = MSG_HDR_VER;
 	hdr->hdr_sz = sizeof(*hdr);
-	hdr->msg_type = type;
-	hdr->msg_version = version;
+	hdr->msg_type = req->msg_type;
+	hdr->msg_version = req->msg_version;
 	hdr->msg_seqno = seqno;
-	hdr->msg_vmpck = vmpck_id;
-	hdr->msg_sz = sz;
+	hdr->msg_vmpck = req->vmpck_id;
+	hdr->msg_sz = req->req_sz;
 
 	/* Verify the sequence number is non-zero */
 	if (!hdr->msg_seqno)
@@ -244,17 +243,17 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
 	pr_debug("request [seqno %lld type %d version %d sz %d]\n",
 		 hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
 
-	if (WARN_ON((sz + ctx->authsize) > sizeof(msg->payload)))
+	if (WARN_ON((req->req_sz + ctx->authsize) > sizeof(msg->payload)))
 		return -EBADMSG;
 
 	memcpy(iv, &hdr->msg_seqno, min(sizeof(iv), sizeof(hdr->msg_seqno)));
-	aesgcm_encrypt(ctx, msg->payload, payload, sz, &hdr->algo, AAD_LEN,
-		       iv, hdr->authtag);
+	aesgcm_encrypt(ctx, msg->payload, req->req_buf, req->req_sz, &hdr->algo,
+		       AAD_LEN, iv, hdr->authtag);
 
 	return 0;
 }
 
-static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
+static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req,
 				  struct snp_guest_request_ioctl *rio)
 {
 	unsigned long req_start = jiffies;
@@ -269,7 +268,7 @@ retry_request:
 	 * sequence number must be incremented or the VMPCK must be deleted to
 	 * prevent reuse of the IV.
 	 */
-	rc = snp_issue_guest_request(exit_code, &snp_dev->input, rio);
+	rc = snp_issue_guest_request(req, &snp_dev->input, rio);
 	switch (rc) {
 	case -ENOSPC:
 		/*
@@ -280,7 +279,7 @@ retry_request:
 		 * IV reuse.
 		 */
 		override_npages = snp_dev->input.data_npages;
-		exit_code	= SVM_VMGEXIT_GUEST_REQUEST;
+		req->exit_code	= SVM_VMGEXIT_GUEST_REQUEST;
 
 		/*
 		 * Override the error to inform callers the given extended
@@ -340,10 +339,8 @@ retry_request:
 	return rc;
 }
 
-static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
-				struct snp_guest_request_ioctl *rio, u8 type,
-				void *req_buf, size_t req_sz, void *resp_buf,
-				u32 resp_sz)
+static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req,
+				  struct snp_guest_request_ioctl *rio)
 {
 	u64 seqno;
 	int rc;
@@ -357,7 +354,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
 
 	/* Encrypt the userspace provided payload in snp_dev->secret_request. */
-	rc = enc_payload(snp_dev, seqno, rio->msg_version, type, req_buf, req_sz);
+	rc = enc_payload(snp_dev, seqno, req);
 	if (rc)
 		return rc;
 
@@ -368,7 +365,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 	memcpy(snp_dev->request, &snp_dev->secret_request,
 	       sizeof(snp_dev->secret_request));
 
-	rc = __handle_guest_request(snp_dev, exit_code, rio);
+	rc = __handle_guest_request(snp_dev, req, rio);
 	if (rc) {
 		if (rc == -EIO &&
 		    rio->exitinfo2 == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
@@ -382,7 +379,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
 		return rc;
 	}
 
-	rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
+	rc = verify_and_dec_payload(snp_dev, req);
 	if (rc) {
 		dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
 		snp_disable_vmpck(snp_dev);
@@ -401,6 +398,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
 {
 	struct snp_report_req *report_req = &snp_dev->req.report;
 	struct snp_report_resp *report_resp;
+	struct snp_guest_req req = {};
 	int rc, resp_len;
 
 	lockdep_assert_held(&snp_cmd_mutex);
@@ -421,8 +419,16 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
 	if (!report_resp)
 		return -ENOMEM;
 
-	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg, SNP_MSG_REPORT_REQ,
-				  report_req, sizeof(*report_req), report_resp->data, resp_len);
+	req.msg_version = arg->msg_version;
+	req.msg_type = SNP_MSG_REPORT_REQ;
+	req.vmpck_id = vmpck_id;
+	req.req_buf = report_req;
+	req.req_sz = sizeof(*report_req);
+	req.resp_buf = report_resp->data;
+	req.resp_sz = resp_len;
+	req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;
+
+	rc = snp_send_guest_request(snp_dev, &req, arg);
 	if (rc)
 		goto e_free;
 
@@ -438,6 +444,7 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
 {
 	struct snp_derived_key_req *derived_key_req = &snp_dev->req.derived_key;
 	struct snp_derived_key_resp derived_key_resp = {0};
+	struct snp_guest_req req = {};
 	int rc, resp_len;
 	/* Response data is 64 bytes and max authsize for GCM is 16 bytes. */
 	u8 buf[64 + 16];
@@ -460,8 +467,16 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
 			   sizeof(*derived_key_req)))
 		return -EFAULT;
 
-	rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg, SNP_MSG_KEY_REQ,
-				  derived_key_req, sizeof(*derived_key_req), buf, resp_len);
+	req.msg_version = arg->msg_version;
+	req.msg_type = SNP_MSG_KEY_REQ;
+	req.vmpck_id = vmpck_id;
+	req.req_buf = derived_key_req;
+	req.req_sz = sizeof(*derived_key_req);
+	req.resp_buf = buf;
+	req.resp_sz = resp_len;
+	req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;
+
+	rc = snp_send_guest_request(snp_dev, &req, arg);
 	if (rc)
 		return rc;
 
@@ -482,6 +497,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
 {
 	struct snp_ext_report_req *report_req = &snp_dev->req.ext_report;
 	struct snp_report_resp *report_resp;
+	struct snp_guest_req req = {};
 	int ret, npages = 0, resp_len;
 	sockptr_t certs_address;
 
@@ -529,9 +545,17 @@ cmd:
 		return -ENOMEM;
 
 	snp_dev->input.data_npages = npages;
-	ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg, SNP_MSG_REPORT_REQ,
-				   &report_req->data, sizeof(report_req->data),
-				   report_resp->data, resp_len);
+
+	req.msg_version = arg->msg_version;
+	req.msg_type = SNP_MSG_REPORT_REQ;
+	req.vmpck_id = vmpck_id;
+	req.req_buf = &report_req->data;
+	req.req_sz = sizeof(report_req->data);
+	req.resp_buf = report_resp->data;
+	req.resp_sz = resp_len;
+	req.exit_code = SVM_VMGEXIT_EXT_GUEST_REQUEST;
+
+	ret = snp_send_guest_request(snp_dev, &req, arg);
 
 	/* If certs length is invalid then copy the returned length */
 	if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) {
@@ -1057,7 +1081,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 	misc->name = DEVICE_NAME;
 	misc->fops = &snp_guest_fops;
 
-	/* initial the input address for guest request */
+	/* Initialize the input addresses for guest request */
 	snp_dev->input.req_gpa = __pa(snp_dev->request);
 	snp_dev->input.resp_gpa = __pa(snp_dev->response);
 	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);