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virt: sev-guest: Carve out SNP message context structure

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Currently, the sev-guest driver is the only user of SNP guest messaging.
The snp_guest_dev structure holds all the allocated buffers, secrets page
and VMPCK details. In preparation for adding messaging allocation and
initialization APIs, decouple snp_guest_dev from messaging-related
information by carving out the guest message context
structure(snp_msg_desc).

Incorporate this newly added context into snp_send_guest_request() and all
related functions, replacing the use of the snp_guest_dev.

No functional change.

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/20241009092850.197575-7-nikunj@amd.com
This commit is contained in:
Nikunj A Dadhania 2024-10-09 14:58:37 +05:30 committed by Borislav Petkov (AMD)
parent ae596615d9
commit 0a895c0d9b
2 changed files with 108 additions and 91 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
arch/x86/include/asm/sev.h
View File

@ -234,6 +234,27 @@ struct snp_secrets_page {
u8 rsvd4[3744];
} __packed;
struct snp_msg_desc {
/* request and response are in unencrypted memory */
struct snp_guest_msg *request, *response;
/*
* Avoid information leakage by double-buffering shared messages
* in fields that are in regular encrypted memory.
*/
struct snp_guest_msg secret_request, secret_response;
struct snp_secrets_page *secrets;
struct snp_req_data input;
void *certs_data;
struct aesgcm_ctx *ctx;
u32 *os_area_msg_seqno;
u8 *vmpck;
};
/*
* The SVSM Calling Area (CA) related structures.
*/

178
drivers/virt/coco/sev-guest/sev-guest.c
View File

@ -40,26 +40,13 @@ struct snp_guest_dev {
struct device *dev;
struct miscdevice misc;
void *certs_data;
struct aesgcm_ctx *ctx;
/* request and response are in unencrypted memory */
struct snp_guest_msg *request, *response;
struct snp_msg_desc *msg_desc;
/*
* Avoid information leakage by double-buffering shared messages
* in fields that are in regular encrypted memory.
*/
struct snp_guest_msg secret_request, secret_response;
struct snp_secrets_page *secrets;
struct snp_req_data input;
union {
struct snp_report_req report;
struct snp_derived_key_req derived_key;
struct snp_ext_report_req ext_report;
} req;
u32 *os_area_msg_seqno;
u8 *vmpck;
};
/*
@ -76,12 +63,12 @@ MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.
/* Mutex to serialize the shared buffer access and command handling. */
static DEFINE_MUTEX(snp_cmd_mutex);
static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
static bool is_vmpck_empty(struct snp_msg_desc *mdesc)
{
char zero_key[VMPCK_KEY_LEN] = {0};
if (snp_dev->vmpck)
return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
if (mdesc->vmpck)
return !memcmp(mdesc->vmpck, zero_key, VMPCK_KEY_LEN);
return true;
}
@ -103,30 +90,30 @@ static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
* vulnerable. If the sequence number were incremented for a fresh IV the ASP
* will reject the request.
*/
static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
static void snp_disable_vmpck(struct snp_msg_desc *mdesc)
{
dev_alert(snp_dev->dev, "Disabling VMPCK%d communication key to prevent IV reuse.\n",
pr_alert("Disabling VMPCK%d communication key to prevent IV reuse.\n",
vmpck_id);
memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
snp_dev->vmpck = NULL;
memzero_explicit(mdesc->vmpck, VMPCK_KEY_LEN);
mdesc->vmpck = NULL;
}
static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
static inline u64 __snp_get_msg_seqno(struct snp_msg_desc *mdesc)
{
u64 count;
lockdep_assert_held(&snp_cmd_mutex);
/* Read the current message sequence counter from secrets pages */
count = *snp_dev->os_area_msg_seqno;
count = *mdesc->os_area_msg_seqno;
return count + 1;
}
/* Return a non-zero on success */
static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
static u64 snp_get_msg_seqno(struct snp_msg_desc *mdesc)
{
u64 count = __snp_get_msg_seqno(snp_dev);
u64 count = __snp_get_msg_seqno(mdesc);
/*
* The message sequence counter for the SNP guest request is a 64-bit
@ -137,20 +124,20 @@ static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
* invalid number and will fail the message request.
*/
if (count >= UINT_MAX) {
dev_err(snp_dev->dev, "request message sequence counter overflow\n");
pr_err("request message sequence counter overflow\n");
return 0;
}
return count;
}
static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
static void snp_inc_msg_seqno(struct snp_msg_desc *mdesc)
{
/*
* The counter is also incremented by the PSP, so increment it by 2
* and save in secrets page.
*/
*snp_dev->os_area_msg_seqno += 2;
*mdesc->os_area_msg_seqno += 2;
}
static inline struct snp_guest_dev *to_snp_dev(struct file *file)
@ -177,13 +164,13 @@ 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, struct snp_guest_req *req)
static int verify_and_dec_payload(struct snp_msg_desc *mdesc, 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;
struct snp_guest_msg *resp_msg = &mdesc->secret_response;
struct snp_guest_msg *req_msg = &mdesc->secret_request;
struct snp_guest_msg_hdr *req_msg_hdr = &req_msg->hdr;
struct snp_guest_msg_hdr *resp_msg_hdr = &resp_msg->hdr;
struct aesgcm_ctx *ctx = snp_dev->ctx;
struct aesgcm_ctx *ctx = mdesc->ctx;
u8 iv[GCM_AES_IV_SIZE] = {};
pr_debug("response [seqno %lld type %d version %d sz %d]\n",
@ -191,7 +178,7 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, struct snp_gues
resp_msg_hdr->msg_sz);
/* Copy response from shared memory to encrypted memory. */
memcpy(resp_msg, snp_dev->response, sizeof(*resp_msg));
memcpy(resp_msg, mdesc->response, sizeof(*resp_msg));
/* Verify that the sequence counter is incremented by 1 */
if (unlikely(resp_msg_hdr->msg_seqno != (req_msg_hdr->msg_seqno + 1)))
@ -218,11 +205,11 @@ static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, struct snp_gues
return 0;
}
static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, struct snp_guest_req *req)
static int enc_payload(struct snp_msg_desc *mdesc, u64 seqno, struct snp_guest_req *req)
{
struct snp_guest_msg *msg = &snp_dev->secret_request;
struct snp_guest_msg *msg = &mdesc->secret_request;
struct snp_guest_msg_hdr *hdr = &msg->hdr;
struct aesgcm_ctx *ctx = snp_dev->ctx;
struct aesgcm_ctx *ctx = mdesc->ctx;
u8 iv[GCM_AES_IV_SIZE] = {};
memset(msg, 0, sizeof(*msg));
@ -253,7 +240,7 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, struct snp_gues
return 0;
}
static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req,
static int __handle_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req,
struct snp_guest_request_ioctl *rio)
{
unsigned long req_start = jiffies;
@ -268,7 +255,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
* sequence number must be incremented or the VMPCK must be deleted to
* prevent reuse of the IV.
*/
rc = snp_issue_guest_request(req, &snp_dev->input, rio);
rc = snp_issue_guest_request(req, &mdesc->input, rio);
switch (rc) {
case -ENOSPC:
/*
@ -278,7 +265,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
* order to increment the sequence number and thus avoid
* IV reuse.
*/
override_npages = snp_dev->input.data_npages;
override_npages = mdesc->input.data_npages;
req->exit_code = SVM_VMGEXIT_GUEST_REQUEST;
/*
@ -318,7 +305,7 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
* structure and any failure will wipe the VMPCK, preventing further
* use anyway.
*/
snp_inc_msg_seqno(snp_dev);
snp_inc_msg_seqno(mdesc);
if (override_err) {
rio->exitinfo2 = override_err;
@ -334,12 +321,12 @@ static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
}
if (override_npages)
snp_dev->input.data_npages = override_npages;
mdesc->input.data_npages = override_npages;
return rc;
}
static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req,
static int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req,
struct snp_guest_request_ioctl *rio)
{
u64 seqno;
@ -348,21 +335,21 @@ static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
guard(mutex)(&snp_cmd_mutex);
/* Check if the VMPCK is not empty */
if (is_vmpck_empty(snp_dev)) {
dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
if (is_vmpck_empty(mdesc)) {
pr_err_ratelimited("VMPCK is disabled\n");
return -ENOTTY;
}
/* Get message sequence and verify that its a non-zero */
seqno = snp_get_msg_seqno(snp_dev);
seqno = snp_get_msg_seqno(mdesc);
if (!seqno)
return -EIO;
/* Clear shared memory's response for the host to populate. */
memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
memset(mdesc->response, 0, sizeof(struct snp_guest_msg));
/* Encrypt the userspace provided payload in snp_dev->secret_request. */
rc = enc_payload(snp_dev, seqno, req);
/* Encrypt the userspace provided payload in mdesc->secret_request. */
rc = enc_payload(mdesc, seqno, req);
if (rc)
return rc;
@ -370,27 +357,26 @@ static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_gues
* Write the fully encrypted request to the shared unencrypted
* request page.
*/
memcpy(snp_dev->request, &snp_dev->secret_request,
sizeof(snp_dev->secret_request));
memcpy(mdesc->request, &mdesc->secret_request,
sizeof(mdesc->secret_request));
rc = __handle_guest_request(snp_dev, req, rio);
rc = __handle_guest_request(mdesc, req, rio);
if (rc) {
if (rc == -EIO &&
rio->exitinfo2 == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
return rc;
dev_alert(snp_dev->dev,
"Detected error from ASP request. rc: %d, exitinfo2: 0x%llx\n",
rc, rio->exitinfo2);
pr_alert("Detected error from ASP request. rc: %d, exitinfo2: 0x%llx\n",
rc, rio->exitinfo2);
snp_disable_vmpck(snp_dev);
snp_disable_vmpck(mdesc);
return rc;
}
rc = verify_and_dec_payload(snp_dev, req);
rc = verify_and_dec_payload(mdesc, req);
if (rc) {
dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
snp_disable_vmpck(snp_dev);
pr_alert("Detected unexpected decode failure from ASP. rc: %d\n", rc);
snp_disable_vmpck(mdesc);
return rc;
}
@ -405,6 +391,7 @@ struct snp_req_resp {
static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
{
struct snp_report_req *report_req = &snp_dev->req.report;
struct snp_msg_desc *mdesc = snp_dev->msg_desc;
struct snp_report_resp *report_resp;
struct snp_guest_req req = {};
int rc, resp_len;
@ -420,7 +407,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
* response payload. Make sure that it has enough space to cover the
* authtag.
*/
resp_len = sizeof(report_resp->data) + snp_dev->ctx->authsize;
resp_len = sizeof(report_resp->data) + mdesc->ctx->authsize;
report_resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
if (!report_resp)
return -ENOMEM;
@ -434,7 +421,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
req.resp_sz = resp_len;
req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;
rc = snp_send_guest_request(snp_dev, &req, arg);
rc = snp_send_guest_request(mdesc, &req, arg);
if (rc)
goto e_free;
@ -450,6 +437,7 @@ 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_msg_desc *mdesc = snp_dev->msg_desc;
struct snp_guest_req req = {};
int rc, resp_len;
/* Response data is 64 bytes and max authsize for GCM is 16 bytes. */
@ -463,7 +451,7 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
* response payload. Make sure that it has enough space to cover the
* authtag.
*/
resp_len = sizeof(derived_key_resp.data) + snp_dev->ctx->authsize;
resp_len = sizeof(derived_key_resp.data) + mdesc->ctx->authsize;
if (sizeof(buf) < resp_len)
return -ENOMEM;
@ -480,7 +468,7 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
req.resp_sz = resp_len;
req.exit_code = SVM_VMGEXIT_GUEST_REQUEST;
rc = snp_send_guest_request(snp_dev, &req, arg);
rc = snp_send_guest_request(mdesc, &req, arg);
if (rc)
return rc;
@ -500,6 +488,7 @@ 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_msg_desc *mdesc = snp_dev->msg_desc;
struct snp_report_resp *report_resp;
struct snp_guest_req req = {};
int ret, npages = 0, resp_len;
@ -533,7 +522,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
* the host. If host does not supply any certs in it, then copy
* zeros to indicate that certificate data was not provided.
*/
memset(snp_dev->certs_data, 0, report_req->certs_len);
memset(mdesc->certs_data, 0, report_req->certs_len);
npages = report_req->certs_len >> PAGE_SHIFT;
cmd:
/*
@ -541,12 +530,12 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
* response payload. Make sure that it has enough space to cover the
* authtag.
*/
resp_len = sizeof(report_resp->data) + snp_dev->ctx->authsize;
resp_len = sizeof(report_resp->data) + mdesc->ctx->authsize;
report_resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
if (!report_resp)
return -ENOMEM;
snp_dev->input.data_npages = npages;
mdesc->input.data_npages = npages;
req.msg_version = arg->msg_version;
req.msg_type = SNP_MSG_REPORT_REQ;
@ -557,11 +546,11 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
req.resp_sz = resp_len;
req.exit_code = SVM_VMGEXIT_EXT_GUEST_REQUEST;
ret = snp_send_guest_request(snp_dev, &req, arg);
ret = snp_send_guest_request(mdesc, &req, arg);
/* If certs length is invalid then copy the returned length */
if (arg->vmm_error == SNP_GUEST_VMM_ERR_INVALID_LEN) {
report_req->certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
report_req->certs_len = mdesc->input.data_npages << PAGE_SHIFT;
if (copy_to_sockptr(io->req_data, report_req, sizeof(*report_req)))
ret = -EFAULT;
@ -570,7 +559,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
if (ret)
goto e_free;
if (npages && copy_to_sockptr(certs_address, snp_dev->certs_data, report_req->certs_len)) {
if (npages && copy_to_sockptr(certs_address, mdesc->certs_data, report_req->certs_len)) {
ret = -EFAULT;
goto e_free;
}
@ -994,6 +983,7 @@ static int __init sev_guest_probe(struct platform_device *pdev)
struct snp_secrets_page *secrets;
struct device *dev = &pdev->dev;
struct snp_guest_dev *snp_dev;
struct snp_msg_desc *mdesc;
struct miscdevice *misc;
void __iomem *mapping;
int ret;
@ -1018,43 +1008,47 @@ static int __init sev_guest_probe(struct platform_device *pdev)
if (!snp_dev)
goto e_unmap;
mdesc = devm_kzalloc(&pdev->dev, sizeof(struct snp_msg_desc), GFP_KERNEL);
if (!mdesc)
goto e_unmap;
/* Adjust the default VMPCK key based on the executing VMPL level */
if (vmpck_id == -1)
vmpck_id = snp_vmpl;
ret = -EINVAL;
snp_dev->vmpck = get_vmpck(vmpck_id, secrets, &snp_dev->os_area_msg_seqno);
if (!snp_dev->vmpck) {
mdesc->vmpck = get_vmpck(vmpck_id, secrets, &mdesc->os_area_msg_seqno);
if (!mdesc->vmpck) {
dev_err(dev, "Invalid VMPCK%d communication key\n", vmpck_id);
goto e_unmap;
}
/* Verify that VMPCK is not zero. */
if (is_vmpck_empty(snp_dev)) {
if (is_vmpck_empty(mdesc)) {
dev_err(dev, "Empty VMPCK%d communication key\n", vmpck_id);
goto e_unmap;
}
platform_set_drvdata(pdev, snp_dev);
snp_dev->dev = dev;
snp_dev->secrets = secrets;
mdesc->secrets = secrets;
/* Allocate the shared page used for the request and response message. */
snp_dev->request = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
if (!snp_dev->request)
mdesc->request = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
if (!mdesc->request)
goto e_unmap;
snp_dev->response = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
if (!snp_dev->response)
mdesc->response = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
if (!mdesc->response)
goto e_free_request;
snp_dev->certs_data = alloc_shared_pages(dev, SEV_FW_BLOB_MAX_SIZE);
if (!snp_dev->certs_data)
mdesc->certs_data = alloc_shared_pages(dev, SEV_FW_BLOB_MAX_SIZE);
if (!mdesc->certs_data)
goto e_free_response;
ret = -EIO;
snp_dev->ctx = snp_init_crypto(snp_dev->vmpck, VMPCK_KEY_LEN);
if (!snp_dev->ctx)
mdesc->ctx = snp_init_crypto(mdesc->vmpck, VMPCK_KEY_LEN);
if (!mdesc->ctx)
goto e_free_cert_data;
misc = &snp_dev->misc;
@ -1063,9 +1057,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
misc->fops = &snp_guest_fops;
/* 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);
mdesc->input.req_gpa = __pa(mdesc->request);
mdesc->input.resp_gpa = __pa(mdesc->response);
mdesc->input.data_gpa = __pa(mdesc->certs_data);
/* Set the privlevel_floor attribute based on the vmpck_id */
sev_tsm_ops.privlevel_floor = vmpck_id;
@ -1082,17 +1076,18 @@ static int __init sev_guest_probe(struct platform_device *pdev)
if (ret)
goto e_free_ctx;
snp_dev->msg_desc = mdesc;
dev_info(dev, "Initialized SEV guest driver (using VMPCK%d communication key)\n", vmpck_id);
return 0;
e_free_ctx:
kfree(snp_dev->ctx);
kfree(mdesc->ctx);
e_free_cert_data:
free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
free_shared_pages(mdesc->certs_data, SEV_FW_BLOB_MAX_SIZE);
e_free_response:
free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
free_shared_pages(mdesc->response, sizeof(struct snp_guest_msg));
e_free_request:
free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
free_shared_pages(mdesc->request, sizeof(struct snp_guest_msg));
e_unmap:
iounmap(mapping);
return ret;
@ -1101,11 +1096,12 @@ static int __init sev_guest_probe(struct platform_device *pdev)
static void __exit sev_guest_remove(struct platform_device *pdev)
{
struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
struct snp_msg_desc *mdesc = snp_dev->msg_desc;
free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
kfree(snp_dev->ctx);
free_shared_pages(mdesc->certs_data, SEV_FW_BLOB_MAX_SIZE);
free_shared_pages(mdesc->response, sizeof(struct snp_guest_msg));
free_shared_pages(mdesc->request, sizeof(struct snp_guest_msg));
kfree(mdesc->ctx);
misc_deregister(&snp_dev->misc);
}