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

[Nikunj A. Dadhania]

On 4/4/2023 1:29 AM, Tom Lendacky wrote:
> 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.

Sure, will create a separate patch.

> 
>>   /*
>>    * 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.

The idea was to get rid of dev_dbg for the movement, will do in a separate 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?

Sure, that should be possible.

> 
>>   {
>> -    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.

Will move to a separate patch.

> 
>>           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.

Right, not necessary here, but will be needed when sev-guest driver calls this after the movement to sev.c. Otherwise, I will need to add this in the movement patch 5/11.

> 
>> +
>>       /* 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?

Yes, can do that.

> 
>>       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.

Sure.

Regards
Nikunj