Re: [PATCH v2 05/11] x86/sev: Move and reorganize sev guest request api
From: Tom Lendacky
Date: Mon Apr 03 2023 - 17:01:49 EST
On 3/26/23 09:46, Nikunj A Dadhania wrote:
For enabling Secure TSC, SEV-SNP guests need to communicate with the
security coprocessor really early during boot. Lot of the required
s/security coprocessor really/AMD Secure Processor/
s/Lot/Many/
functions are implemented in the sev-guest driver. Move the required
... in the sev-guest driver and therefore not available at early boot.
functions and provide API to the driver to assign VM communications
s/provide API/provide an API/
s/to assign.*//
key and send guest request.
Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
---
arch/x86/Kconfig | 1 +
.../x86/include/asm}/sev-guest.h | 6 +
arch/x86/include/asm/sev.h | 22 +
arch/x86/kernel/sev.c | 437 ++++++++++++++++-
drivers/virt/coco/sev-guest/Kconfig | 1 -
drivers/virt/coco/sev-guest/sev-guest.c | 455 ++----------------
6 files changed, 487 insertions(+), 435 deletions(-)
rename {drivers/virt/coco/sev-guest => arch/x86/include/asm}/sev-guest.h (86%)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a825bf031f49..42c52bfd2bac 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1545,6 +1545,7 @@ config AMD_MEM_ENCRYPT
select INSTRUCTION_DECODER
select ARCH_HAS_CC_PLATFORM
select X86_MEM_ENCRYPT
+ 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/drivers/virt/coco/sev-guest/sev-guest.h b/arch/x86/include/asm/sev-guest.h
similarity index 86%
rename from drivers/virt/coco/sev-guest/sev-guest.h
rename to arch/x86/include/asm/sev-guest.h
index d245578d988e..834cdae302ad 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.h
+++ b/arch/x86/include/asm/sev-guest.h
@@ -12,6 +12,9 @@
#include <linux/types.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
#define AAD_LEN 48
@@ -72,6 +75,9 @@ struct snp_guest_req {
u8 msg_type;
};
+int snp_send_guest_request(struct snp_guest_dev *dev, struct snp_guest_req *req);
+bool snp_assign_vmpck(struct snp_guest_dev *dev, int vmpck_id);
+
static inline bool is_vmpck_empty(u8 *vmpck)
{
char zero_key[VMPCK_KEY_LEN] = {0};
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ebc271bb6d8e..36868e21c3e0 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -9,6 +9,7 @@
#define __ASM_ENCRYPTED_STATE_H
#include <linux/types.h>
+#include <linux/miscdevice.h>
#include <asm/insn.h>
#include <asm/sev-common.h>
#include <asm/bootparam.h>
@@ -96,6 +97,27 @@ struct snp_req_data {
struct sev_guest_platform_data {
u64 secrets_gpa;
+
+ void *certs_data;
+ struct aesgcm_ctx *ctx;
+ struct snp_guest_msg *req, *resp;
+ struct snp_secrets_page_layout *layout;
+ struct snp_req_data input;
+ u8 *vmpck0;
Isn't this unneeded? You have the vmpck and vmpck_id in the snp_guest_dev
struct which will be set based on the module parameter, so vmpck0 and
associated checks shouldn't be needed.
+};
+
+struct snp_guest_dev {
+ struct device *dev;
+ struct miscdevice misc;
+
+ /* Mutex to serialize the shared buffer access and command handling. */
+ struct mutex cmd_mutex;
+
+ struct sev_guest_platform_data *pdata;
+
+ u32 *os_area_msg_seqno;
+ u8 *vmpck;
+ u8 vmpck_id;
};
/*
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 3f664ab277c4..c5ca97aab8c1 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -22,10 +22,13 @@
#include <linux/efi.h>
#include <linux/platform_device.h>
#include <linux/io.h>
+#include <linux/psp-sev.h>
+#include <crypto/gcm.h>
#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>
@@ -982,6 +985,427 @@ static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa)
free_page((unsigned long)vmsa);
}
+static struct sev_guest_platform_data *platform_data;
+
+/*
+ * 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)
+{
+ pr_alert("Disabling vmpck_id %d to prevent IV reuse.\n", snp_dev->vmpck_id);
+ memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
+ snp_dev->vmpck = NULL;
+}
+
+static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u64 count;
+
+ lockdep_assert_held(&snp_dev->cmd_mutex);
+
+ /* Read the current message sequence counter from secrets pages */
+ count = *snp_dev->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)
+{
+ /*
+ * 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;
+}
+
+static struct aesgcm_ctx *snp_init_crypto(u8 *key, size_t keylen)
+{
+ struct aesgcm_ctx *ctx;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
+ if (!ctx)
+ return NULL;
+
+ if (aesgcm_expandkey(ctx, key, keylen, AUTHTAG_LEN)) {
+ pr_err("SNP: crypto init failed\n");
+ kfree(ctx);
+ return NULL;
+ }
+
+ return ctx;
+}
+
+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);
+}
+
+static int snp_setup_psp_messaging(struct sev_guest_platform_data *pdata)
+{
+ u64 gpa;
+ int ret;
+
+ if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+ return -ENODEV;
+
+ gpa = get_secrets_page();
+ if (!gpa)
+ return -ENODEV;
+
+ pdata->layout = (__force void *)ioremap_encrypted(gpa, PAGE_SIZE);
+ if (!pdata->layout) {
+ pr_err("Unable to locate AP jump table address: failed to map the SNP secrets page.\n");
+ return -ENODEV;
+ }
+
+ ret = -EINVAL;
+ pdata->vmpck0 = pdata->layout->vmpck0;
+
+ /* Verify that VMPCK is not zero. */
+ if (is_vmpck_empty(pdata->vmpck0)) {
+ pr_err("vmpck id 0 is null\n");
+ goto e_unmap;
+ }
+
+ ret = -ENOMEM;
+ /* Allocate the shared page used for the request and response message. */
+ pdata->req = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!pdata->req)
+ goto e_unmap;
+
+ pdata->resp = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!pdata->resp)
+ goto e_free_request;
+
+ pdata->certs_data = alloc_shared_pages(SEV_FW_BLOB_MAX_SIZE);
+ if (!pdata->certs_data)
+ goto e_free_response;
+
+ ret = -EIO;
+ pdata->ctx = snp_init_crypto(pdata->vmpck0, VMPCK_KEY_LEN);
+ if (!pdata->ctx)
+ goto e_free_cert_data;
+
+ /* initial the input address for guest request */
+ pdata->input.req_gpa = __pa(pdata->req);
+ pdata->input.resp_gpa = __pa(pdata->resp);
+ pdata->input.data_gpa = __pa(pdata->certs_data);
+
+ return 0;
+
+e_free_cert_data:
+ free_shared_pages(pdata->certs_data, SEV_FW_BLOB_MAX_SIZE);
+e_free_response:
+ free_shared_pages(pdata->resp, sizeof(struct snp_guest_msg));
+e_free_request:
+ free_shared_pages(pdata->req, sizeof(struct snp_guest_msg));
+e_unmap:
+ iounmap(pdata->layout);
+
+ return ret;
+}
+
+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 sev_guest_platform_data *pdata,
+ void *payload, u32 sz)
+{
+ struct snp_guest_msg *resp = pdata->resp;
+ struct snp_guest_msg *req = pdata->req;
+ struct snp_guest_msg_hdr *req_hdr = &req->hdr;
+ struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
+ struct aesgcm_ctx *ctx = pdata->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);
+
+ /* 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) > sz))
+ return -EBADMSG;
+
+ return dec_payload(ctx, resp, payload, resp_hdr->msg_sz);
+}
+
+static int enc_payload(struct sev_guest_platform_data *pdata, u64 seqno,
+ struct snp_guest_req *req, u8 vmpck_id)
+{
+ struct snp_guest_msg *msg = pdata->req;
+ 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 = 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(pdata->ctx, msg, req->req_buf, req->req_sz);
+}
+
+static int __handle_guest_request(struct snp_guest_dev *snp_dev,
+ struct sev_guest_platform_data *pdata,
+ struct snp_guest_req *req)
+{
+ unsigned long err = 0xff, override_err = 0;
+ unsigned long req_start = jiffies;
+ unsigned int override_npages = 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->exit_code, &pdata->input, &err);
+ 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 = pdata->input.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_REQ_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_EBUSY 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 (req->fw_err)
+ *req->fw_err = override_err ?: err;
+
+ if (override_npages)
+ pdata->input.data_npages = override_npages;
+
+ /*
+ * 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_REQ_INVALID_LEN)
+ return -EIO;
+
+ return rc;
+}
+
+int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req)
+{
+ struct sev_guest_platform_data *pdata;
+ u64 seqno;
+ int rc;
+
+ if (!snp_dev || !snp_dev->pdata || !req)
+ 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;
+
+ memset(pdata->resp, 0, sizeof(struct snp_guest_msg));
+
+ /* Encrypt the provided payload */
+ rc = enc_payload(pdata, seqno, req, snp_dev->vmpck_id);
+ if (rc)
+ return rc;
+
+ rc = __handle_guest_request(snp_dev, pdata, req);
+ if (rc) {
+ if (rc == -EIO && *req->fw_err == SNP_GUEST_REQ_INVALID_LEN)
+ return rc;
+
+ pr_alert("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(pdata, req->resp_buf, req->resp_sz);
+ 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, int vmpck_id)
+{
+ struct sev_guest_platform_data *pdata = dev->pdata;
+
+ if (!pdata || WARN_ON(vmpck_id > 3))
+ return false;
+
+ dev->vmpck_id = vmpck_id;
+ dev->vmpck = pdata->layout->vmpck0 + vmpck_id * VMPCK_KEY_LEN;
+ dev->os_area_msg_seqno = &pdata->layout->os_area.msg_seqno_0 + 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;
@@ -2247,18 +2671,17 @@ static struct platform_device sev_guest_device = {
static int __init snp_init_platform_device(void)
{
- struct sev_guest_platform_data data;
- u64 gpa;
-
if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
return -ENODEV;
- gpa = get_secrets_page();
- if (!gpa)
+ platform_data = kzalloc(sizeof(*platform_data), GFP_KERNEL);
+ if (!platform_data)
+ return -ENOMEM;
+
+ if (snp_setup_psp_messaging(platform_data))
This shouldn't be done here (or yet) since you only moving the routines.
The sev-guest driver should call this regardless of the vmpck_id value.
return -ENODEV;
- data.secrets_gpa = gpa;
- if (platform_device_add_data(&sev_guest_device, &data, sizeof(data)))
+ if (platform_device_add_data(&sev_guest_device, platform_data, sizeof(*platform_data)))
return -ENODEV;
if (platform_device_register(&sev_guest_device))
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 4901ebc8fa1a..a011df21c03a 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -24,110 +24,25 @@
#include <asm/svm.h>
#include <asm/sev.h>
-#include "sev-guest.h"
+#include <asm/sev-guest.h>
#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;
- struct snp_guest_msg *request, *response;
- struct snp_secrets_page_layout *layout;
- struct snp_req_data input;
- u32 *os_area_msg_seqno;
- u8 *vmpck;
- u8 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.");
static inline unsigned int get_ctx_authsize(struct snp_guest_dev *snp_dev)
{
- if (snp_dev && snp_dev->ctx)
- return snp_dev->ctx->authsize;
+ struct sev_guest_platform_data *pdata = snp_dev->pdata;
+
+ if (pdata && pdata->ctx)
+ return pdata->ctx->authsize;
WARN_ONCE(1, "Unable to get crypto authsize\n");
return 0;
}
-/*
- * 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)
-{
- dev_alert(snp_dev->dev, "Disabling vmpck_id %d to prevent IV reuse.\n",
- snp_dev->vmpck_id);
- memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
- snp_dev->vmpck = NULL;
-}
-
-static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
-{
- u64 count;
-
- lockdep_assert_held(&snp_dev->cmd_mutex);
-
- /* Read the current message sequence counter from secrets pages */
- count = *snp_dev->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)
-{
- /*
- * 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;
-}
-
static inline struct snp_guest_dev *to_snp_dev(struct file *file)
{
struct miscdevice *dev = file->private_data;
@@ -135,236 +50,6 @@ 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(u8 *key, size_t keylen)
-{
- struct aesgcm_ctx *ctx;
-
- ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
- if (!ctx)
- return NULL;
-
- if (aesgcm_expandkey(ctx, key, keylen, 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, void *payload, u32 sz)
-{
- struct snp_guest_msg *resp = snp_dev->response;
- struct snp_guest_msg *req = snp_dev->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);
-
- /* 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) > sz))
- return -EBADMSG;
-
- /* Decrypt the payload */
- return dec_payload(ctx, resp, payload, resp_hdr->msg_sz);
-}
-
-static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno,
- struct snp_guest_req *req, u8 __vmpck_id)
-{
- struct snp_guest_msg *msg = snp_dev->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 = __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)
-{
- unsigned long err = 0xff, override_err = 0;
- unsigned long req_start = jiffies;
- unsigned int override_npages = 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->exit_code, &snp_dev->input, &err);
- 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 = snp_dev->input.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_REQ_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_EBUSY 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 (req->fw_err)
- *req->fw_err = override_err ?: err;
-
- if (override_npages)
- snp_dev->input.data_npages = override_npages;
-
- /*
- * 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_REQ_INVALID_LEN)
- return -EIO;
-
- return rc;
-}
-
-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;
-
- /* Get message sequence and verify that its a non-zero */
- seqno = snp_get_msg_seqno(snp_dev);
- if (!seqno)
- return -EIO;
-
- memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
-
- /* Encrypt the userspace provided payload */
- rc = enc_payload(snp_dev, seqno, req, snp_dev->vmpck_id);
- if (rc)
- return rc;
-
- rc = __handle_guest_request(snp_dev, req);
- if (rc) {
- 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, *req->fw_err);
- snp_disable_vmpck(snp_dev);
- return rc;
- }
-
- rc = verify_and_dec_payload(snp_dev, req->resp_buf, req->resp_sz);
- 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 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)
@@ -463,12 +148,14 @@ 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 sev_guest_platform_data *pdata;
struct snp_ext_report_req req;
struct snp_report_resp *resp;
int ret, npages = 0, resp_len;
lockdep_assert_held(&snp_dev->cmd_mutex);
+ pdata = snp_dev->pdata;
if (!arg->req_data || !arg->resp_data)
return -EINVAL;
@@ -492,7 +179,7 @@ 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, req.certs_len);
+ memset(pdata->certs_data, 0, req.certs_len);
npages = req.certs_len >> PAGE_SHIFT;
cmd:
/*
@@ -505,14 +192,14 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
if (!resp)
return -ENOMEM;
- snp_dev->input.data_npages = npages;
+ pdata->input.data_npages = npages;
ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
SNP_MSG_REPORT_REQ, &req.data,
sizeof(req.data), resp->data, resp_len, &arg->fw_err);
/* If certs length is invalid then copy the returned length */
if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
- req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
+ req.certs_len = pdata->input.data_npages << PAGE_SHIFT;
if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
ret = -EFAULT;
@@ -522,7 +209,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
goto e_free;
if (npages &&
- copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
+ copy_to_user((void __user *)req.certs_address, pdata->certs_data,
req.certs_len)) {
ret = -EFAULT;
goto e_free;
@@ -583,68 +270,17 @@ 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;
- dev->vmpck = dev->layout->vmpck0 + vmpck_id * VMPCK_KEY_LEN;
- dev->os_area_msg_seqno = &dev->layout->os_area.msg_seqno_0 + 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 sev_guest_platform_data *pdata;
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))
@@ -653,80 +289,48 @@ static int __init sev_guest_probe(struct platform_device *pdev)
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;
+ pdata = (struct sev_guest_platform_data *)dev->platform_data;
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;
+ snp_dev->pdata = pdata;
if (!snp_assign_vmpck(snp_dev, vmpck_id)) {
dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
- goto e_unmap;
+ goto e_free_snpdev;
}
/* Verify that VMPCK is not zero. */
if (is_vmpck_empty(snp_dev->vmpck)) {
dev_err(dev, "vmpck id %d is null\n", vmpck_id);
- goto e_unmap;
+ goto e_free_snpdev;
+ }
+
+ /* Skip VMPCK0 initialization as the key is already initialized during early boot */
+ if (vmpck_id && aesgcm_expandkey(pdata->ctx, snp_dev->vmpck, VMPCK_KEY_LEN, AUTHTAG_LEN)) {
See previous comment. The sev-guest driver should be setting up everything
private to it no matter the vmpck to be used.
Thanks,
Tom
+ 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);
- if (!snp_dev->certs_data)
- goto e_free_response;
-
- ret = -EIO;
- snp_dev->ctx = snp_init_crypto(snp_dev->vmpck, VMPCK_KEY_LEN);
- if (!snp_dev->ctx)
- goto e_free_cert_data;
-
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);
- snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
-
- ret = misc_register(misc);
+ ret = misc_register(misc);
if (ret)
- goto e_free_ctx;
+ goto e_free_snpdev;
dev_info(dev, "Initialized SEV guest driver (using vmpck_id %d)\n", 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_snpdev:
+ kfree(snp_dev);
return ret;
}
@@ -734,11 +338,8 @@ 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);
return 0;
}