Re: [PATCH v5 04/14] virt: sev-guest: Add SNP guest request structure
From: Nikunj A. Dadhania
Date: Thu Nov 02 2023 - 00:03:50 EST
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@xxxxxxx>
>
> 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