[PATCH v5 07/14] x86/sev: Move and reorganize sev guest request api

Nikunj A Dadhania
2023-10-30T06:38:34Z

For enabling Secure TSC, SEV-SNP guests need to communicate with the
AMD Security Processor early during boot. Many of the required
functions are implemented in the sev-guest driver and therefore not
available at early boot. Move the required functions and provide an
API to the driver to assign key and send guest request.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/sev-guest.h | 84 +++-
arch/x86/include/asm/sev.h | 10 -
arch/x86/kernel/sev.c | 466 ++++++++++++++++++++++-
drivers/virt/coco/sev-guest/Kconfig | 1 -
drivers/virt/coco/sev-guest/sev-guest.c | 486 +-----------------------
6 files changed, 555 insertions(+), 493 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 66bfabae8814..245a18f6910a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1509,6 +1509,7 @@ config AMD_MEM_ENCRYPT
select ARCH_HAS_CC_PLATFORM
select X86_MEM_ENCRYPT
select UNACCEPTED_MEMORY
+ select CRYPTO_LIB_AESGCM
help
Say yes to enable support for the encryption of system memory.
This requires an AMD processor that supports Secure Memory
diff --git a/arch/x86/include/asm/sev-guest.h b/arch/x86/include/asm/sev-guest.h
index 22ef97b55069..e6f94208173d 100644
--- a/arch/x86/include/asm/sev-guest.h
+++ b/arch/x86/include/asm/sev-guest.h
@@ -11,6 +11,11 @@
#define __VIRT_SEVGUEST_H__

#include <linux/types.h>
+#include <linux/miscdevice.h>
+#include <asm/sev.h>
+
+#define SNP_REQ_MAX_RETRY_DURATION (60*HZ)
+#define SNP_REQ_RETRY_DELAY (2*HZ)

#define MAX_AUTHTAG_LEN 32
#define AUTHTAG_LEN 16
@@ -58,11 +63,45 @@ struct snp_guest_msg_hdr {
u8 rsvd3[35];
} __packed;

+/* SNP Guest message request */
+struct snp_req_data {
+ unsigned long req_gpa;
+ unsigned long resp_gpa;
+};
+
struct snp_guest_msg {
struct snp_guest_msg_hdr hdr;
u8 payload[4000];
} __packed;

+struct sev_guest_platform_data {
+ /* request and response are in unencrypted memory */
+ struct snp_guest_msg *request, *response;
+
+ struct snp_secrets_page_layout *layout;
+ struct snp_req_data input;
+};
+
+struct snp_guest_dev {
+ struct device *dev;
+ struct miscdevice misc;
+
+ /* Mutex to serialize the shared buffer access and command handling. */
+ struct mutex cmd_mutex;
+
+ void *certs_data;
+ struct aesgcm_ctx *ctx;
+
+ /*
+ * 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 sev_guest_platform_data *pdata;
+ unsigned int vmpck_id;
+};
+
struct snp_guest_req {
void *req_buf, *resp_buf, *data;
size_t req_sz, resp_sz, *data_npages;
@@ -72,6 +111,47 @@ struct snp_guest_req {
u8 msg_type;
};

-int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_data *input,
- struct snp_guest_request_ioctl *rio);
+int snp_setup_psp_messaging(struct snp_guest_dev *snp_dev);
+int snp_send_guest_request(struct snp_guest_dev *dev, struct snp_guest_req *req,
+ struct snp_guest_request_ioctl *rio);
+bool snp_assign_vmpck(struct snp_guest_dev *dev, unsigned int vmpck_id);
+bool snp_is_vmpck_empty(unsigned int vmpck_id);
+
+static void free_shared_pages(void *buf, size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ int ret;
+
+ if (!buf)
+ return;
+
+ ret = set_memory_encrypted((unsigned long)buf, npages);
+ if (ret) {
+ WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
+ return;
+ }
+
+ __free_pages(virt_to_page(buf), get_order(sz));
+}
+
+static void *alloc_shared_pages(size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ struct page *page;
+ int ret;
+
+ page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
+ if (!page)
+ return NULL;
+
+ ret = set_memory_decrypted((unsigned long)page_address(page), npages);
+ if (ret) {
+ pr_err("%s: failed to mark page shared, ret=%d\n", __func__, ret);
+ __free_pages(page, get_order(sz));
+ return NULL;
+ }
+
+ return page_address(page);
+}
+
#endif /* __VIRT_SEVGUEST_H__ */
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 78465a8c7dc6..783150458864 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -93,16 +93,6 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs);

#define RMPADJUST_VMSA_PAGE_BIT BIT(16)

-/* SNP Guest message request */
-struct snp_req_data {
- unsigned long req_gpa;
- unsigned long resp_gpa;
-};
-
-struct sev_guest_platform_data {
- u64 secrets_gpa;
-};
-
/*
* The secrets page contains 96-bytes of reserved field that can be used by
* the guest OS. The guest OS uses the area to save the message sequence
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index fd3b822fa9e7..fb3b1feb1b84 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -24,6 +24,7 @@
#include <linux/io.h>
#include <linux/psp-sev.h>
#include <uapi/linux/sev-guest.h>
+#include <crypto/gcm.h>

#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
@@ -941,6 +942,457 @@ static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa)
free_page((unsigned long)vmsa);
}

+static struct sev_guest_platform_data *platform_data;
+
+static inline u8 *snp_get_vmpck(unsigned int vmpck_id)
+{
+ if (!platform_data)
+ return NULL;
+
+ return platform_data->layout->vmpck0 + vmpck_id * VMPCK_KEY_LEN;
+}
+
+static inline u32 *snp_get_os_area_msg_seqno(unsigned int vmpck_id)
+{
+ if (!platform_data)
+ return NULL;
+
+ return &platform_data->layout->os_area.msg_seqno_0 + vmpck_id;
+}
+
+bool snp_is_vmpck_empty(unsigned int vmpck_id)
+{
+ char zero_key[VMPCK_KEY_LEN] = {0};
+ u8 *key = snp_get_vmpck(vmpck_id);
+
+ if (key)
+ return !memcmp(key, zero_key, VMPCK_KEY_LEN);
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(snp_is_vmpck_empty);
+
+/*
+ * 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
+ * using the VMPCK.
+ *
+ * This is because in the current encryption scheme GHCB v2 uses AES-GCM to
+ * encrypt the requests. The IV for this scheme is the sequence number. GCM
+ * cannot tolerate IV reuse.
+ *
+ * The ASP FW v1.51 only increments the sequence numbers on a successful
+ * guest<->ASP back and forth and only accepts messages at its exact sequence
+ * number.
+ *
+ * So if the sequence number were to be reused the encryption scheme is
+ * 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)
+{
+ u8 *key = snp_get_vmpck(snp_dev->vmpck_id);
+
+ pr_alert("Disabling vmpck_id %d to prevent IV reuse.\n", snp_dev->vmpck_id);
+ memzero_explicit(key, VMPCK_KEY_LEN);
+}
+
+static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u32 *os_area_msg_seqno = snp_get_os_area_msg_seqno(snp_dev->vmpck_id);
+ u64 count;
+
+ if (!os_area_msg_seqno) {
+ pr_err("SNP unable to get message sequence counter\n");
+ return 0;
+ }
+
+ lockdep_assert_held(&snp_dev->cmd_mutex);
+
+ /* Read the current message sequence counter from secrets pages */
+ count = *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)
+{
+ u64 count = __snp_get_msg_seqno(snp_dev);
+
+ /*
+ * The message sequence counter for the SNP guest request is a 64-bit
+ * value but the version 2 of GHCB specification defines a 32-bit storage
+ * for it. If the counter exceeds the 32-bit value then return zero.
+ * The caller should check the return value, but if the caller happens to
+ * not check the value and use it, then the firmware treats zero as an
+ * invalid number and will fail the message request.
+ */
+ if (count >= UINT_MAX) {
+ pr_err("SNP request message sequence counter overflow\n");
+ return 0;
+ }
+
+ return count;
+}
+
+static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u32 *os_area_msg_seqno = snp_get_os_area_msg_seqno(snp_dev->vmpck_id);
+
+ if (!os_area_msg_seqno) {
+ pr_err("SNP unable to get message sequence counter\n");
+ return;
+ }
+
+ /*
+ * The counter is also incremented by the PSP, so increment it by 2
+ * and save in secrets page.
+ */
+ *os_area_msg_seqno += 2;
+}
+
+static struct aesgcm_ctx *snp_init_crypto(unsigned int vmpck_id)
+{
+ struct aesgcm_ctx *ctx;
+ u8 *key;
+
+ if (snp_is_vmpck_empty(vmpck_id)) {
+ pr_err("SNP: vmpck id %d is null\n", vmpck_id);
+ return NULL;
+ }
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
+ if (!ctx)
+ return NULL;
+
+ key = snp_get_vmpck(vmpck_id);
+ if (aesgcm_expandkey(ctx, key, VMPCK_KEY_LEN, AUTHTAG_LEN)) {
+ pr_err("SNP: crypto init failed\n");
+ kfree(ctx);
+ return NULL;
+ }
+
+ return ctx;
+}
+
+int snp_setup_psp_messaging(struct snp_guest_dev *snp_dev)
+{
+ struct sev_guest_platform_data *pdata;
+ int ret;
+
+ if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
+ pr_err("SNP not supported\n");
+ return 0;
+ }
+
+ if (platform_data) {
+ pr_debug("SNP platform data already initialized.\n");
+ goto create_ctx;
+ }
+
+ if (!secrets_pa) {
+ pr_err("SNP no secrets page\n");
+ return -ENODEV;
+ }
+
+ pdata = kzalloc(sizeof(struct sev_guest_platform_data), GFP_KERNEL);
+ if (!pdata) {
+ pr_err("SNP alloc failed\n");
+ return -ENOMEM;
+ }
+
+ pdata->layout = (__force void *)ioremap_encrypted(secrets_pa, PAGE_SIZE);
+ if (!pdata->layout) {
+ pr_err("Unable to locate AP jump table address: failed to map the SNP secrets page.\n");
+ goto e_free_pdata;
+ }
+
+ ret = -ENOMEM;
+ /* Allocate the shared page used for the request and response message. */
+ pdata->request = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!pdata->request)
+ goto e_unmap;
+
+ pdata->response = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!pdata->response)
+ goto e_free_request;
+
+ /* initial the input address for guest request */
+ pdata->input.req_gpa = __pa(pdata->request);
+ pdata->input.resp_gpa = __pa(pdata->response);
+ platform_data = pdata;
+
+create_ctx:
+ ret = -EIO;
+ snp_dev->ctx = snp_init_crypto(snp_dev->vmpck_id);
+ if (!snp_dev->ctx) {
+ pr_err("SNP init crypto failed\n");
+ platform_data = NULL;
+ goto e_free_response;
+ }
+
+ snp_dev->pdata = platform_data;
+ return 0;
+
+e_free_response:
+ free_shared_pages(pdata->response, sizeof(struct snp_guest_msg));
+e_free_request:
+ free_shared_pages(pdata->request, sizeof(struct snp_guest_msg));
+e_unmap:
+ iounmap(pdata->layout);
+e_free_pdata:
+ kfree(pdata);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(snp_setup_psp_messaging);
+
+static int __enc_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+ u8 iv[GCM_AES_IV_SIZE] = {};
+
+ if (WARN_ON((hdr->msg_sz + ctx->authsize) > sizeof(msg->payload)))
+ return -EBADMSG;
+
+ memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+ aesgcm_encrypt(ctx, msg->payload, plaintext, len, &hdr->algo, AAD_LEN,
+ iv, hdr->authtag);
+ return 0;
+}
+
+static int dec_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+ u8 iv[GCM_AES_IV_SIZE] = {};
+
+ memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+ if (aesgcm_decrypt(ctx, plaintext, msg->payload, len, &hdr->algo,
+ AAD_LEN, iv, hdr->authtag))
+ return 0;
+ else
+ return -EBADMSG;
+}
+
+static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_req *guest_req,
+ struct sev_guest_platform_data *pdata)
+{
+ struct snp_guest_msg *resp = &snp_dev->secret_response;
+ struct snp_guest_msg *req = &snp_dev->secret_request;
+ struct snp_guest_msg_hdr *req_hdr = &req->hdr;
+ struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
+ struct aesgcm_ctx *ctx = snp_dev->ctx;
+
+ 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);
+
+ /* Copy response from shared memory to encrypted memory. */
+ memcpy(resp, pdata->response, sizeof(*resp));
+
+ /* Verify that the sequence counter is incremented by 1 */
+ if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
+ return -EBADMSG;
+
+ /* Verify response message type and version number. */
+ if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
+ resp_hdr->msg_version != req_hdr->msg_version)
+ return -EBADMSG;
+
+ /*
+ * If the message size is greater than our buffer length then return
+ * an error.
+ */
+ if (unlikely((resp_hdr->msg_sz + ctx->authsize) > guest_req->resp_sz))
+ return -EBADMSG;
+
+ 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, struct snp_guest_req *req)
+{
+ struct snp_guest_msg *msg = &snp_dev->secret_request;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+
+ 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 = req->msg_type;
+ hdr->msg_version = req->msg_version;
+ hdr->msg_seqno = seqno;
+ hdr->msg_vmpck = req->vmpck_id;
+ hdr->msg_sz = req->req_sz;
+
+ /* Verify the sequence number is non-zero */
+ if (!hdr->msg_seqno)
+ return -ENOSR;
+
+ 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, msg, req->req_buf, req->req_sz);
+}
+
+static int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_data *input,
+ struct snp_guest_request_ioctl *rio);
+
+static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req,
+ struct snp_guest_request_ioctl *rio,
+ struct sev_guest_platform_data *pdata)
+{
+ unsigned long req_start = jiffies;
+ unsigned int override_npages = 0;
+ u64 override_err = 0;
+ int rc;
+
+retry_request:
+ /*
+ * Call firmware to process the request. In this function the encrypted
+ * message enters shared memory with the host. So after this call the
+ * sequence number must be incremented or the VMPCK must be deleted to
+ * prevent reuse of the IV.
+ */
+ rc = snp_issue_guest_request(req, &pdata->input, rio);
+ switch (rc) {
+ case -ENOSPC:
+ /*
+ * If the extended guest request fails due to having too
+ * small of a certificate data buffer, retry the same
+ * guest request without the extended data request in
+ * order to increment the sequence number and thus avoid
+ * IV reuse.
+ */
+ override_npages = *req->data_npages;
+ req->exit_code = SVM_VMGEXIT_GUEST_REQUEST;
+
+ /*
+ * Override the error to inform callers the given extended
+ * request buffer size was too small and give the caller the
+ * required buffer size.
+ */
+ override_err = SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN);
+
+ /*
+ * If this call to the firmware succeeds, the sequence number can
+ * be incremented allowing for continued use of the VMPCK. If
+ * there is an error reflected in the return value, this value
+ * is checked further down and the result will be the deletion
+ * of the VMPCK and the error code being propagated back to the
+ * user as an ioctl() return code.
+ */
+ goto retry_request;
+
+ /*
+ * The host may return SNP_GUEST_REQ_ERR_BUSY if the request has been
+ * throttled. Retry in the driver to avoid returning and reusing the
+ * message sequence number on a different message.
+ */
+ case -EAGAIN:
+ if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) {
+ rc = -ETIMEDOUT;
+ break;
+ }
+ schedule_timeout_killable(SNP_REQ_RETRY_DELAY);
+ goto retry_request;
+ }
+
+ /*
+ * Increment the message sequence number. There is no harm in doing
+ * this now because decryption uses the value stored in the response
+ * structure and any failure will wipe the VMPCK, preventing further
+ * use anyway.
+ */
+ snp_inc_msg_seqno(snp_dev);
+
+ if (override_err) {
+ rio->exitinfo2 = override_err;
+
+ /*
+ * If an extended guest request was issued and the supplied certificate
+ * buffer was not large enough, a standard guest request was issued to
+ * prevent IV reuse. If the standard request was successful, return -EIO
+ * back to the caller as would have originally been returned.
+ */
+ if (!rc && override_err == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
+ rc = -EIO;
+ }
+
+ if (override_npages)
+ *req->data_npages = override_npages;
+
+ return rc;
+}
+
+int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req,
+ struct snp_guest_request_ioctl *rio)
+{
+ struct sev_guest_platform_data *pdata;
+ u64 seqno;
+ int rc;
+
+ if (!snp_dev || !snp_dev->pdata || !req || !rio)
+ return -ENODEV;
+
+ pdata = snp_dev->pdata;
+
+ /* Get message sequence and verify that its a non-zero */
+ seqno = snp_get_msg_seqno(snp_dev);
+ if (!seqno)
+ return -EIO;
+
+ /* Clear shared memory's response for the host to populate. */
+ memset(pdata->response, 0, sizeof(struct snp_guest_msg));
+
+ /* Encrypt the userspace provided payload in pdata->secret_request. */
+ rc = enc_payload(snp_dev, seqno, req);
+ if (rc)
+ return rc;
+
+ /*
+ * Write the fully encrypted request to the shared unencrypted
+ * request page.
+ */
+ memcpy(pdata->request, &snp_dev->secret_request, sizeof(snp_dev->secret_request));
+
+ rc = __handle_guest_request(snp_dev, req, rio, pdata);
+ if (rc) {
+ if (rc == -EIO &&
+ rio->exitinfo2 == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
+ return rc;
+
+ pr_alert("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, req, pdata);
+ if (rc) {
+ pr_alert("Detected unexpected decode failure from ASP. rc: %d\n", rc);
+ snp_disable_vmpck(snp_dev);
+ return rc;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(snp_send_guest_request);
+
+bool snp_assign_vmpck(struct snp_guest_dev *dev, unsigned int vmpck_id)
+{
+ if (WARN_ON(vmpck_id > 3))
+ return false;
+
+ dev->vmpck_id = vmpck_id;
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(snp_assign_vmpck);
+
static int wakeup_cpu_via_vmgexit(int apic_id, unsigned long start_ip)
{
struct sev_es_save_area *cur_vmsa, *vmsa;
@@ -2150,8 +2602,8 @@ static int __init init_sev_config(char *str)
}
__setup("sev=", init_sev_config);

-int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_data *input,
- struct snp_guest_request_ioctl *rio)
+static 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;
@@ -2218,7 +2670,6 @@ int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_data *inpu

return ret;
}
-EXPORT_SYMBOL_GPL(snp_issue_guest_request);

static struct platform_device sev_guest_device = {
.name = "sev-guest",
@@ -2227,18 +2678,9 @@ static struct platform_device sev_guest_device = {

static int __init snp_init_platform_device(void)
{
- struct sev_guest_platform_data data;
-
if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
return -ENODEV;

- if (!secrets_pa)
- return -ENODEV;
-
- data.secrets_gpa = secrets_pa;
- if (platform_device_add_data(&sev_guest_device, &data, sizeof(data)))
- return -ENODEV;
-
if (platform_device_register(&sev_guest_device))
return -ENODEV;

diff --git a/drivers/virt/coco/sev-guest/Kconfig b/drivers/virt/coco/sev-guest/Kconfig
index bcc760bfb468..c130456ad401 100644
--- a/drivers/virt/coco/sev-guest/Kconfig
+++ b/drivers/virt/coco/sev-guest/Kconfig
@@ -2,7 +2,6 @@ config SEV_GUEST
tristate "AMD SEV Guest driver"
default m
depends on AMD_MEM_ENCRYPT
- select CRYPTO_LIB_AESGCM
help
SEV-SNP firmware provides the guest a mechanism to communicate with
the PSP without risk from a malicious hypervisor who wishes to read,
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 4dd094c73e2f..062ff12b030e 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -27,32 +27,6 @@

#define DEVICE_NAME "sev-guest"

-#define SNP_REQ_MAX_RETRY_DURATION (60*HZ)
-#define SNP_REQ_RETRY_DELAY (2*HZ)
-
-struct snp_guest_dev {
- struct device *dev;
- struct miscdevice misc;
-
- /* Mutex to serialize the shared buffer access and command handling. */
- struct mutex cmd_mutex;
-
- void *certs_data;
- struct aesgcm_ctx *ctx;
- /* 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_layout *layout;
- struct snp_req_data input;
- unsigned int vmpck_id;
-};
-
static u32 vmpck_id;
module_param(vmpck_id, uint, 0444);
MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
@@ -60,95 +34,6 @@ 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 inline u8 *snp_get_vmpck(struct snp_guest_dev *snp_dev)
-{
- return snp_dev->layout->vmpck0 + snp_dev->vmpck_id * VMPCK_KEY_LEN;
-}
-
-static inline u32 *snp_get_os_area_msg_seqno(struct snp_guest_dev *snp_dev)
-{
- return &snp_dev->layout->os_area.msg_seqno_0 + snp_dev->vmpck_id;
-}
-
-static bool snp_is_vmpck_empty(struct snp_guest_dev *snp_dev)
-{
- char zero_key[VMPCK_KEY_LEN] = {0};
- u8 *key = snp_get_vmpck(snp_dev);
-
- return !memcmp(key, zero_key, VMPCK_KEY_LEN);
-}
-
-/*
- * 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
- * using the VMPCK.
- *
- * This is because in the current encryption scheme GHCB v2 uses AES-GCM to
- * encrypt the requests. The IV for this scheme is the sequence number. GCM
- * cannot tolerate IV reuse.
- *
- * The ASP FW v1.51 only increments the sequence numbers on a successful
- * guest<->ASP back and forth and only accepts messages at its exact sequence
- * number.
- *
- * So if the sequence number were to be reused the encryption scheme is
- * 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)
-{
- u8 *key = snp_get_vmpck(snp_dev);
-
- dev_alert(snp_dev->dev, "Disabling vmpck_id %d to prevent IV reuse.\n",
- snp_dev->vmpck_id);
- memzero_explicit(key, VMPCK_KEY_LEN);
-}
-
-static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
-{
- u32 *os_area_msg_seqno = snp_get_os_area_msg_seqno(snp_dev);
- u64 count;
-
- lockdep_assert_held(&snp_dev->cmd_mutex);
-
- /* Read the current message sequence counter from secrets pages */
- count = *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)
-{
- u64 count = __snp_get_msg_seqno(snp_dev);
-
- /*
- * The message sequence counter for the SNP guest request is a 64-bit
- * value but the version 2 of GHCB specification defines a 32-bit storage
- * for it. If the counter exceeds the 32-bit value then return zero.
- * The caller should check the return value, but if the caller happens to
- * not check the value and use it, then the firmware treats zero as an
- * invalid number and will fail the message request.
- */
- if (count >= UINT_MAX) {
- dev_err(snp_dev->dev, "request message sequence counter overflow\n");
- return 0;
- }
-
- return count;
-}
-
-static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
-{
- u32 *os_area_msg_seqno = snp_get_os_area_msg_seqno(snp_dev);
-
- /*
- * The counter is also incremented by the PSP, so increment it by 2
- * and save in secrets page.
- */
- *os_area_msg_seqno += 2;
-}
-
static inline struct snp_guest_dev *to_snp_dev(struct file *file)
{
struct miscdevice *dev = file->private_data;
@@ -156,255 +41,6 @@ static inline struct snp_guest_dev *to_snp_dev(struct file *file)
return container_of(dev, struct snp_guest_dev, misc);
}

-static struct aesgcm_ctx *snp_init_crypto(struct snp_guest_dev *snp_dev)
-{
- struct aesgcm_ctx *ctx;
- u8 *key;
-
- if (snp_is_vmpck_empty(snp_dev)) {
- pr_err("SNP: vmpck id %d is null\n", snp_dev->vmpck_id);
- return NULL;
- }
-
- ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
- if (!ctx)
- return NULL;
-
- key = snp_get_vmpck(snp_dev);
- if (aesgcm_expandkey(ctx, key, VMPCK_KEY_LEN, AUTHTAG_LEN)) {
- pr_err("SNP: crypto init failed\n");
- kfree(ctx);
- return NULL;
- }
-
- return ctx;
-}
-
-static int __enc_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
- void *plaintext, size_t len)
-{
- struct snp_guest_msg_hdr *hdr = &msg->hdr;
- u8 iv[GCM_AES_IV_SIZE] = {};
-
- if (WARN_ON((hdr->msg_sz + ctx->authsize) > sizeof(msg->payload)))
- return -EBADMSG;
-
- memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
- aesgcm_encrypt(ctx, msg->payload, plaintext, len, &hdr->algo, AAD_LEN,
- iv, hdr->authtag);
- return 0;
-}
-
-static int dec_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
- void *plaintext, size_t len)
-{
- struct snp_guest_msg_hdr *hdr = &msg->hdr;
- u8 iv[GCM_AES_IV_SIZE] = {};
-
- memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
- if (aesgcm_decrypt(ctx, plaintext, msg->payload, len, &hdr->algo,
- AAD_LEN, iv, hdr->authtag))
- return 0;
- else
- return -EBADMSG;
-}
-
-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;
- struct snp_guest_msg_hdr *req_hdr = &req->hdr;
- struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
- struct aesgcm_ctx *ctx = snp_dev->ctx;
-
- 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);
-
- /* Copy response from shared memory to encrypted memory. */
- memcpy(resp, snp_dev->response, sizeof(*resp));
-
- /* Verify that the sequence counter is incremented by 1 */
- if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
- return -EBADMSG;
-
- /* Verify response message type and version number. */
- if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
- resp_hdr->msg_version != req_hdr->msg_version)
- return -EBADMSG;
-
- /*
- * If the message size is greater than our buffer length then return
- * an error.
- */
- if (unlikely((resp_hdr->msg_sz + ctx->authsize) > guest_req->resp_sz))
- return -EBADMSG;
-
- /* Decrypt the payload */
- 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, struct snp_guest_req *req)
-{
- struct snp_guest_msg *msg = &snp_dev->secret_request;
- struct snp_guest_msg_hdr *hdr = &msg->hdr;
-
- 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 = req->msg_type;
- hdr->msg_version = req->msg_version;
- hdr->msg_seqno = seqno;
- hdr->msg_vmpck = req->vmpck_id;
- hdr->msg_sz = req->req_sz;
-
- /* Verify the sequence number is non-zero */
- if (!hdr->msg_seqno)
- return -ENOSR;
-
- 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, msg, req->req_buf, req->req_sz);
-}
-
-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;
- unsigned int override_npages = 0;
- u64 override_err = 0;
- int rc;
-
-retry_request:
- /*
- * Call firmware to process the request. In this function the encrypted
- * message enters shared memory with the host. So after this call the
- * 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);
- switch (rc) {
- case -ENOSPC:
- /*
- * If the extended guest request fails due to having too
- * small of a certificate data buffer, retry the same
- * guest request without the extended data request in
- * order to increment the sequence number and thus avoid
- * IV reuse.
- */
- override_npages = *req->data_npages;
- req->exit_code = SVM_VMGEXIT_GUEST_REQUEST;
-
- /*
- * Override the error to inform callers the given extended
- * request buffer size was too small and give the caller the
- * required buffer size.
- */
- override_err = SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN);
-
- /*
- * If this call to the firmware succeeds, the sequence number can
- * be incremented allowing for continued use of the VMPCK. If
- * there is an error reflected in the return value, this value
- * is checked further down and the result will be the deletion
- * of the VMPCK and the error code being propagated back to the
- * user as an ioctl() return code.
- */
- goto retry_request;
-
- /*
- * The host may return SNP_GUEST_VMM_ERR_BUSY if the request has been
- * throttled. Retry in the driver to avoid returning and reusing the
- * message sequence number on a different message.
- */
- case -EAGAIN:
- if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) {
- rc = -ETIMEDOUT;
- break;
- }
- schedule_timeout_killable(SNP_REQ_RETRY_DELAY);
- goto retry_request;
- }
-
- /*
- * Increment the message sequence number. There is no harm in doing
- * this now because decryption uses the value stored in the response
- * structure and any failure will wipe the VMPCK, preventing further
- * use anyway.
- */
- snp_inc_msg_seqno(snp_dev);
-
- if (override_err) {
- rio->exitinfo2 = override_err;
-
- /*
- * If an extended guest request was issued and the supplied certificate
- * buffer was not large enough, a standard guest request was issued to
- * prevent IV reuse. If the standard request was successful, return -EIO
- * back to the caller as would have originally been returned.
- */
- if (!rc && override_err == SNP_GUEST_VMM_ERR(SNP_GUEST_VMM_ERR_INVALID_LEN))
- rc = -EIO;
- }
-
- if (override_npages)
- *req->data_npages = override_npages;
-
- return rc;
-}
-
-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;
-
- /* Get message sequence and verify that its a non-zero */
- seqno = snp_get_msg_seqno(snp_dev);
- if (!seqno)
- return -EIO;
-
- /* Clear shared memory's response for the host to populate. */
- 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, req);
- if (rc)
- return rc;
-
- /*
- * Write the fully encrypted request to the shared unencrypted
- * request page.
- */
- memcpy(snp_dev->request, &snp_dev->secret_request,
- sizeof(snp_dev->secret_request));
-
- 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))
- return rc;
-
- 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, req);
- if (rc) {
- dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
- snp_disable_vmpck(snp_dev);
- return rc;
- }
-
- return 0;
-}
-
static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
{
struct snp_guest_req guest_req = {0};
@@ -604,7 +240,7 @@ 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 (snp_is_vmpck_empty(snp_dev)) {
+ if (snp_is_vmpck_empty(snp_dev->vmpck_id)) {
dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
mutex_unlock(&snp_dev->cmd_mutex);
return -ENOTTY;
@@ -632,147 +268,63 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
return ret;
}

-static void free_shared_pages(void *buf, size_t sz)
-{
- unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
- int ret;
-
- if (!buf)
- return;
-
- ret = set_memory_encrypted((unsigned long)buf, npages);
- if (ret) {
- WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
- return;
- }
-
- __free_pages(virt_to_page(buf), get_order(sz));
-}
-
-static void *alloc_shared_pages(struct device *dev, size_t sz)
-{
- unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
- struct page *page;
- int ret;
-
- page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
- if (!page)
- return NULL;
-
- ret = set_memory_decrypted((unsigned long)page_address(page), npages);
- if (ret) {
- dev_err(dev, "failed to mark page shared, ret=%d\n", ret);
- __free_pages(page, get_order(sz));
- return NULL;
- }
-
- return page_address(page);
-}
-
static const struct file_operations snp_guest_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = snp_guest_ioctl,
};

-bool snp_assign_vmpck(struct snp_guest_dev *dev, int vmpck_id)
-{
- if (WARN_ON(vmpck_id > 3))
- return false;
-
- dev->vmpck_id = vmpck_id;
-
- return true;
-}
-
static int __init sev_guest_probe(struct platform_device *pdev)
{
- struct snp_secrets_page_layout *layout;
- struct sev_guest_platform_data *data;
struct device *dev = &pdev->dev;
struct snp_guest_dev *snp_dev;
struct miscdevice *misc;
- void __iomem *mapping;
int ret;

if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
return -ENODEV;

- if (!dev->platform_data)
- return -ENODEV;
-
- data = (struct sev_guest_platform_data *)dev->platform_data;
- mapping = ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
- if (!mapping)
- return -ENODEV;
-
- layout = (__force void *)mapping;
-
- ret = -ENOMEM;
snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
if (!snp_dev)
- goto e_unmap;
+ return -ENOMEM;

- ret = -EINVAL;
- snp_dev->layout = layout;
if (!snp_assign_vmpck(snp_dev, vmpck_id)) {
dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
- goto e_unmap;
+ ret = -EINVAL;
+ goto e_free_snpdev;
}

- /* Verify that VMPCK is not zero. */
- if (snp_is_vmpck_empty(snp_dev)) {
- dev_err(dev, "vmpck id %d is null\n", vmpck_id);
- goto e_unmap;
+ if (snp_setup_psp_messaging(snp_dev)) {
+ dev_err(dev, "Unable to setup PSP messaging vmpck id %d\n", snp_dev->vmpck_id);
+ ret = -ENODEV;
+ goto e_free_snpdev;
}

mutex_init(&snp_dev->cmd_mutex);
platform_set_drvdata(pdev, snp_dev);
snp_dev->dev = dev;

- /* 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)
- goto e_unmap;
-
- snp_dev->response = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
- if (!snp_dev->response)
- goto e_free_request;
-
- snp_dev->certs_data = alloc_shared_pages(dev, SEV_FW_BLOB_MAX_SIZE);
+ snp_dev->certs_data = alloc_shared_pages(SEV_FW_BLOB_MAX_SIZE);
if (!snp_dev->certs_data)
- goto e_free_response;
-
- ret = -EIO;
- snp_dev->ctx = snp_init_crypto(snp_dev);
- if (!snp_dev->ctx)
- goto e_free_cert_data;
+ goto e_free_ctx;

misc = &snp_dev->misc;
misc->minor = MISC_DYNAMIC_MINOR;
misc->name = DEVICE_NAME;
misc->fops = &snp_guest_fops;

- /* initial the input address for guest request */
- snp_dev->input.req_gpa = __pa(snp_dev->request);
- snp_dev->input.resp_gpa = __pa(snp_dev->response);
-
ret = misc_register(misc);
if (ret)
- goto e_free_ctx;
+ goto e_free_cert_data;

- dev_info(dev, "Initialized SEV guest driver (using vmpck_id %d)\n", vmpck_id);
+ dev_info(dev, "Initialized SEV guest driver (using vmpck_id %d)\n", snp_dev->vmpck_id);
return 0;

-e_free_ctx:
- kfree(snp_dev->ctx);
e_free_cert_data:
free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
-e_free_response:
- free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
-e_free_request:
- free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
-e_unmap:
- iounmap(mapping);
+ e_free_ctx:
+ kfree(snp_dev->ctx);
+e_free_snpdev:
+ kfree(snp_dev);
return ret;
}

@@ -780,11 +332,9 @@ static int __exit sev_guest_remove(struct platform_device *pdev)
{
struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);

- 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);
misc_deregister(&snp_dev->misc);
+ kfree(snp_dev->ctx);
+ kfree(snp_dev);

return 0;
}
--
2.34.1