Re: [PATCH v2 03/11] virt: sev-guest: Add snp_guest_req structure

From: Tom Lendacky
Date: Mon Apr 03 2023 - 15:59:09 EST

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On 3/26/23 09:46, Nikunj A Dadhania wrote:

Add a snp_guest_req structure to simplify the function arguments. The
structure will be used to call the SNP Guest message request API
instead of passing a long list of parameters.

Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
---
drivers/virt/coco/sev-guest/sev-guest.c | 87 ++++++++++++++-----------
drivers/virt/coco/sev-guest/sev-guest.h | 19 ++++++
2 files changed, 68 insertions(+), 38 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 6ae197b57644..ec93dee330f2 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -60,16 +60,6 @@ static inline unsigned int get_ctx_authsize(struct snp_guest_dev *snp_dev)
return 0;
}
-static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
-{
- char zero_key[VMPCK_KEY_LEN] = {0};
-
- if (snp_dev->vmpck)
- return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
-
- return true;
-}
-

This change seems separate from the changes for snp_guest_req.

/*
* If an error is received from the host or AMD Secure Processor (ASP) there
* are two options. Either retry the exact same encrypted request or discontinue
@@ -198,8 +188,9 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload,
struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
struct aesgcm_ctx *ctx = snp_dev->ctx;
- dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
- resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
+ pr_debug("response [seqno %lld type %d version %d sz %d]\n",
+ resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version,
+ resp_hdr->msg_sz);

Again, not related to the purpose of this patch.

/* Verify that the sequence counter is incremented by 1 */
if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
@@ -221,34 +212,34 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload,
return dec_payload(ctx, resp, payload, resp_hdr->msg_sz);
}
-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, u8 __vmpck_id)

Can the vmpck_id be part of the snp_guest_req structure?

{
- struct snp_guest_msg *req = snp_dev->request;
- struct snp_guest_msg_hdr *hdr = &req->hdr;
+ struct snp_guest_msg *msg = snp_dev->request;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
- memset(req, 0, sizeof(*req));
+ memset(msg, 0, sizeof(*msg));
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 = __vmpck_id;
+ hdr->msg_sz = req->req_sz;
/* Verify the sequence number is non-zero */
if (!hdr->msg_seqno)
return -ENOSR;
- dev_dbg(snp_dev->dev, "request [seqno %lld type %d version %d sz %d]\n",
+ pr_debug("request [seqno %lld type %d version %d sz %d]\n",

Unrelated change.

hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
- return __enc_payload(snp_dev->ctx, req, payload, sz);
+ return __enc_payload(snp_dev->ctx, msg, req->req_buf, req->req_sz);
}
-static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, __u64 *fw_err)
+static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req)
{
unsigned long err = 0xff, override_err = 0;
unsigned long req_start = jiffies;
@@ -262,7 +253,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
* 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, &err);
+ rc = snp_issue_guest_request(req->exit_code, &snp_dev->input, &err);
switch (rc) {
case -ENOSPC:
/*
@@ -273,7 +264,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
* 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
@@ -314,8 +305,8 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
*/
snp_inc_msg_seqno(snp_dev);
- if (fw_err)
- *fw_err = override_err ?: err;
+ if (req->fw_err)
+ *req->fw_err = override_err ?: err;
if (override_npages)
snp_dev->input.data_npages = override_npages;
@@ -332,13 +323,14 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
return rc;
}
-static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
- u8 type, void *req_buf, size_t req_sz, void *resp_buf,
- u32 resp_sz, __u64 *fw_err)
+static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req)
{
u64 seqno;
int rc;
+ if (!snp_dev || !req)
+ return -ENODEV;

This seems unrelated, at least the check for snp_dev. And looking at the only caller, a guest request is always provided. So this seems unnecessary - at least at this point in the series.

+
/* Get message sequence and verify that its a non-zero */
seqno = snp_get_msg_seqno(snp_dev);
if (!seqno)
@@ -347,21 +339,22 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
/* Encrypt the userspace provided payload */
- rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
+ rc = enc_payload(snp_dev, seqno, req, vmpck_id);
if (rc)
return rc;
- rc = __handle_guest_request(snp_dev, exit_code, fw_err);
+ rc = __handle_guest_request(snp_dev, req);
if (rc) {
- if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN)
+ if (rc == -EIO && *req->fw_err == SNP_GUEST_REQ_INVALID_LEN)
return rc;
- dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n", rc, *fw_err);
+ dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n",
+ rc, *req->fw_err);
snp_disable_vmpck(snp_dev);
return rc;
}
- rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
+ rc = verify_and_dec_payload(snp_dev, req->resp_buf, req->resp_sz);

Can't you just pass req here?

if (rc) {
dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
snp_disable_vmpck(snp_dev);
@@ -371,6 +364,24 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
return 0;
}
+
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, u8 msg_version,
+ u8 msg_type, void *req_buf, size_t req_sz, void *resp_buf,
+ u32 resp_sz, __u64 *fw_err)
+{
+ struct snp_guest_req guest_req = {
+ .msg_version = msg_version,
+ .msg_type = msg_type,
+ .req_buf = req_buf,
+ .req_sz = req_sz,
+ .resp_buf = resp_buf,
+ .resp_sz = resp_sz,
+ .fw_err = fw_err,
+ .exit_code = exit_code,
+ };

Add a blank line here.

Thanks,
Tom

+ return snp_send_guest_request(snp_dev, &guest_req);
+}
+
static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
{
struct snp_report_resp *resp;
@@ -544,7 +555,7 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
mutex_lock(&snp_dev->cmd_mutex);
/* Check if the VMPCK is not empty */
- if (is_vmpck_empty(snp_dev)) {
+ if (is_vmpck_empty(snp_dev->vmpck)) {
dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
mutex_unlock(&snp_dev->cmd_mutex);
return -ENOTTY;
@@ -678,7 +689,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
}
/* Verify that VMPCK is not zero. */
- if (is_vmpck_empty(snp_dev)) {
+ if (is_vmpck_empty(snp_dev->vmpck)) {
dev_err(dev, "vmpck id %d is null\n", vmpck_id);
goto e_unmap;
}
diff --git a/drivers/virt/coco/sev-guest/sev-guest.h b/drivers/virt/coco/sev-guest/sev-guest.h
index ceb798a404d6..d245578d988e 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.h
+++ b/drivers/virt/coco/sev-guest/sev-guest.h
@@ -63,4 +63,23 @@ struct snp_guest_msg {
u8 payload[4000];
} __packed;
+struct snp_guest_req {
+ void *req_buf, *resp_buf;
+ size_t req_sz, resp_sz;
+ u64 exit_code;
+ u64 *fw_err;
+ u8 msg_version;
+ u8 msg_type;
+};
+
+static inline bool is_vmpck_empty(u8 *vmpck)
+{
+ char zero_key[VMPCK_KEY_LEN] = {0};
+
+ if (vmpck)
+ return !memcmp(vmpck, zero_key, VMPCK_KEY_LEN);
+
+ return true;
+}
+
#endif /* __VIRT_SEVGUEST_H__ */

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Next in thread: Nikunj A. Dadhania: "Re: [PATCH v2 03/11] virt: sev-guest: Add snp_guest_req structure"
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