Re: [PATCH v5 04/14] virt: sev-guest: Add SNP guest request structure

Nikunj A. Dadhania
2023-11-02T04:01:41Z

On 10/30/2023 11:46 PM, Tom Lendacky wrote:
> On 10/30/23 01:36, 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@amd.com>
>
> Some minor comments below.
>
>> ---
>>   .../x86/include/asm}/sev-guest.h              |  11 ++
>>   arch/x86/include/asm/sev.h                    |   8 --
>>   arch/x86/kernel/sev.c                         |  15 ++-
>>   drivers/virt/coco/sev-guest/sev-guest.c       | 103 +++++++++++-------
>>   4 files changed, 84 insertions(+), 53 deletions(-)
>>   rename {drivers/virt/coco/sev-guest => arch/x86/include/asm}/sev-guest.h (80%)
>>
>> diff --git a/drivers/virt/coco/sev-guest/sev-guest.h b/arch/x86/include/asm/sev-guest.h
>> similarity index 80%
>> rename from drivers/virt/coco/sev-guest/sev-guest.h
>> rename to arch/x86/include/asm/sev-guest.h
>> index ceb798a404d6..22ef97b55069 100644
>> --- a/drivers/virt/coco/sev-guest/sev-guest.h
>> +++ b/arch/x86/include/asm/sev-guest.h
>> @@ -63,4 +63,15 @@ struct snp_guest_msg {
>>       u8 payload[4000];
>>   } __packed;
>>   +struct snp_guest_req {
>> +    void *req_buf, *resp_buf, *data;
>> +    size_t req_sz, resp_sz, *data_npages;
>
> For structures like this, I find it easier to group things and keep it one item per line, e.g.:

Ok, I will change that.

>     void *req_buf;
>     size_t req_sz;
>
>     void *resp_buf;
>     size_t resp_sz;
>
>     void *data;
>     size_t *data_npages;
>
> And does data_npages have to be a pointer?

Going through the code again, you are right, it need not be a pointer.

> It looks like you can just use this variable as the address on the GHCB call and then set it appropriately without all the indirection, right?

I can use the data_npages value directly in the GHCB call, am I missing something.

@@ -2192,8 +2199,8 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct sn
vc_ghcb_invalidate(ghcb);
if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
- ghcb_set_rax(ghcb, input->data_gpa);
- ghcb_set_rbx(ghcb, input->data_npages);
+ ghcb_set_rax(ghcb, __pa(req->data));
+ ghcb_set_rbx(ghcb, req->data_npages);
}
ret = sev_es_ghcb_hv_call(ghcb, &ctxt, exit_code, input->req_gpa, input->resp_gpa);
@@ -2212,7 +2219,7 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct sn
case SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN):
/* Number of expected pages are returned in RBX */
if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
- input->data_npages = ghcb_get_rbx(ghcb);
+ req->data_npages = ghcb_get_rbx(ghcb);
ret = -ENOSPC;
break;
}

>
>> +    u64 exit_code;
>> +    unsigned int vmpck_id;
>> +    u8 msg_version;
>> +    u8 msg_type;
>> +};
>> +
>> +int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_data *input,
>> +                struct snp_guest_request_ioctl *rio);
>>   #endif /* __VIRT_SEVGUEST_H__ */
>> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
>> index 5b4a1ce3d368..78465a8c7dc6 100644
>> --- a/arch/x86/include/asm/sev.h
>> +++ b/arch/x86/include/asm/sev.h
>> @@ -97,8 +97,6 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs);
>>   struct snp_req_data {
>>       unsigned long req_gpa;
>>       unsigned long resp_gpa;
>> -    unsigned long data_gpa;
>> -    unsigned int data_npages;
>>   };
>>     struct sev_guest_platform_data {
>> @@ -209,7 +207,6 @@ void snp_set_memory_private(unsigned long vaddr, unsigned long npages);
>>   void snp_set_wakeup_secondary_cpu(void);
>>   bool snp_init(struct boot_params *bp);
>>   void __init __noreturn snp_abort(void);
>> -int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio);
>>   void snp_accept_memory(phys_addr_t start, phys_addr_t end);
>>   u64 snp_get_unsupported_features(u64 status);
>>   u64 sev_get_status(void);
>> @@ -233,11 +230,6 @@ static inline void snp_set_memory_private(unsigned long vaddr, unsigned long npa
>>   static inline void snp_set_wakeup_secondary_cpu(void) { }
>>   static inline bool snp_init(struct boot_params *bp) { return false; }
>>   static inline void snp_abort(void) { }
>> -static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio)
>> -{
>> -    return -ENOTTY;
>> -}
>> -
>
> May want to mention in the commit message why this can be deleted vs changed.

Sure will do. It has been moved to sev-guest.h now.

>
>>   static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
>>   static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
>>   static inline u64 sev_get_status(void) { return 0; }
>> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
>> index 6395bfd87b68..f8caf0a73052 100644
>> --- a/arch/x86/kernel/sev.c
>> +++ b/arch/x86/kernel/sev.c
>> @@ -28,6 +28,7 @@
>>   #include <asm/cpu_entry_area.h>
>>   #include <asm/stacktrace.h>
>>   #include <asm/sev.h>
>> +#include <asm/sev-guest.h>
>>   #include <asm/insn-eval.h>
>>   #include <asm/fpu/xcr.h>
>>   #include <asm/processor.h>
>> @@ -2167,15 +2168,21 @@ static int __init init_sev_config(char *str)
>>   }
>>   __setup("sev=", init_sev_config);
>>   -int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio)
>> +int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_data *input,
>> +                struct snp_guest_request_ioctl *rio)
>>   {
>>       struct ghcb_state state;
>>       struct es_em_ctxt ctxt;
>>       unsigned long flags;
>>       struct ghcb *ghcb;
>> +    u64 exit_code;
>>       int ret;
>>         rio->exitinfo2 = SEV_RET_NO_FW_CALL;
>> +    if (!req)
>> +        return -EINVAL;
>> +
>> +    exit_code = req->exit_code;
>>         /*
>>        * __sev_get_ghcb() needs to run with IRQs disabled because it is using
>> @@ -2192,8 +2199,8 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct sn
>>       vc_ghcb_invalidate(ghcb);
>>         if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
>> -        ghcb_set_rax(ghcb, input->data_gpa);
>> -        ghcb_set_rbx(ghcb, input->data_npages);
>> +        ghcb_set_rax(ghcb, __pa(req->data));
>> +        ghcb_set_rbx(ghcb, *req->data_npages);
>>       }
>>         ret = sev_es_ghcb_hv_call(ghcb, &ctxt, exit_code, input->req_gpa, input->resp_gpa);
>> @@ -2212,7 +2219,7 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct sn
>>       case SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN):
>>           /* Number of expected pages are returned in RBX */
>>           if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
>> -            input->data_npages = ghcb_get_rbx(ghcb);
>> +            *req->data_npages = ghcb_get_rbx(ghcb);
>>               ret = -ENOSPC;
>>               break;
>>           }
>> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
>> index 49bafd2e9f42..5801dd52ffdf 100644
>> --- a/drivers/virt/coco/sev-guest/sev-guest.c
>> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
>> @@ -23,8 +23,7 @@
>>     #include <asm/svm.h>
>>   #include <asm/sev.h>
>> -
>> -#include "sev-guest.h"
>> +#include <asm/sev-guest.h>
>>     #define DEVICE_NAME    "sev-guest"
>>   @@ -192,7 +191,7 @@ static int dec_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
>>           return -EBADMSG;
>>   }
>>   -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 *guest_req)
>>   {
>>       struct snp_guest_msg *resp = &snp_dev->secret_response;
>>       struct snp_guest_msg *req = &snp_dev->secret_request;
>> @@ -220,29 +219,28 @@ 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_hdr->msg_sz + ctx->authsize) > sz))
>> +    if (unlikely((resp_hdr->msg_sz + ctx->authsize) > guest_req->resp_sz))
>>           return -EBADMSG;
>>         /* Decrypt the payload */
>> -    return dec_payload(ctx, resp, payload, resp_hdr->msg_sz);
>> +    return dec_payload(ctx, resp, guest_req->resp_buf, 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)
>>   {
>> -    struct snp_guest_msg *req = &snp_dev->secret_request;
>> -    struct snp_guest_msg_hdr *hdr = &req->hdr;
>> +    struct snp_guest_msg *msg = &snp_dev->secret_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 = req->vmpck_id;
>> +    hdr->msg_sz = req->req_sz;
>>         /* Verify the sequence number is non-zero */
>>       if (!hdr->msg_seqno)
>> @@ -251,10 +249,10 @@ 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);
>>   -    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,
>> +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 +267,7 @@ 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, rio);
>> +    rc = snp_issue_guest_request(req, &snp_dev->input, rio);
>>       switch (rc) {
>>       case -ENOSPC:
>>           /*
>> @@ -279,8 +277,8 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
>>            * order to increment the sequence number and thus avoid
>>            * IV reuse.
>>            */
>> -        override_npages = snp_dev->input.data_npages;
>> -        exit_code    = SVM_VMGEXIT_GUEST_REQUEST;
>> +        override_npages = *req->data_npages;
>> +        req->exit_code    = SVM_VMGEXIT_GUEST_REQUEST;
>>             /*
>>            * Override the error to inform callers the given extended
>> @@ -335,15 +333,13 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
>>       }
>>         if (override_npages)
>> -        snp_dev->input.data_npages = override_npages;
>> +        *req->data_npages = override_npages;
>>         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 +353,7 @@ 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 +364,7 @@ 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))
>> @@ -377,12 +373,11 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
>>           dev_alert(snp_dev->dev,
>>                 "Detected error from ASP request. rc: %d, exitinfo2: 0x%llx\n",
>>                 rc, rio->exitinfo2);
>> -
>>           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);
>>       if (rc) {
>>           dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
>>           snp_disable_vmpck(snp_dev);
>> @@ -394,6 +389,7 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
>>     static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
>>   {
>> +    struct snp_guest_req guest_req = {0};
>>       struct snp_report_resp *resp;
>>       struct snp_report_req req;
>>       int rc, resp_len;
>> @@ -416,9 +412,16 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
>>       if (!resp)
>>           return -ENOMEM;
>>   -    rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
>> -                  SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
>> -                  resp_len);
>> +    guest_req.msg_version = arg->msg_version;
>> +    guest_req.msg_type = SNP_MSG_REPORT_REQ;
>> +    guest_req.vmpck_id = vmpck_id;
>> +    guest_req.req_buf = &req;
>> +    guest_req.req_sz = sizeof(req);
>> +    guest_req.resp_buf = resp->data;
>> +    guest_req.resp_sz = resp_len;
>> +    guest_req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;
>> +
>> +    rc = snp_send_guest_request(snp_dev, &guest_req, arg);
>>       if (rc)
>>           goto e_free;
>>   @@ -433,6 +436,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
>>   static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
>>   {
>>       struct snp_derived_key_resp resp = {0};
>> +    struct snp_guest_req guest_req = {0};
>>       struct snp_derived_key_req req;
>>       int rc, resp_len;
>>       /* Response data is 64 bytes and max authsize for GCM is 16 bytes. */
>> @@ -455,8 +459,16 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
>>       if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
>>           return -EFAULT;
>>   -    rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg,
>> -                  SNP_MSG_KEY_REQ, &req, sizeof(req), buf, resp_len);
>> +    guest_req.msg_version = arg->msg_version;
>> +    guest_req.msg_type = SNP_MSG_KEY_REQ;
>> +    guest_req.vmpck_id = vmpck_id;
>> +    guest_req.req_buf = &req;
>> +    guest_req.req_sz = sizeof(req);
>> +    guest_req.resp_buf = buf;
>> +    guest_req.resp_sz = resp_len;
>> +    guest_req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;
>> +
>> +    rc = snp_send_guest_request(snp_dev, &guest_req, arg);
>>       if (rc)
>>           return rc;
>>   @@ -472,9 +484,11 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
>>     static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
>>   {
>> +    struct snp_guest_req guest_req = {0};
>>       struct snp_ext_report_req req;
>>       struct snp_report_resp *resp;
>> -    int ret, npages = 0, resp_len;
>> +    int ret, resp_len;
>> +    size_t npages = 0;
>
> This becomes unnecessary if you don't define data_npages as a pointer in the snp_guest_req structure.

Right, I will change that.

>
> Thanks,
> Tom

Thanks
Nikunj