Re: [PATCH v9 41/43] virt: Add SEV-SNP guest driver

Peter Gonda
2022-02-01T20:33:35Z

On Fri, Jan 28, 2022 at 10:19 AM Brijesh Singh <brijesh.singh@amd.com> wrote:
>
> SEV-SNP specification provides the guest a mechanism to communicate with
> the PSP without risk from a malicious hypervisor who wishes to read, alter,
> drop or replay the messages sent. The driver uses snp_issue_guest_request()
> to issue GHCB SNP_GUEST_REQUEST or SNP_EXT_GUEST_REQUEST NAE events to
> submit the request to PSP.
>
> The PSP requires that all communication should be encrypted using key
> specified through the platform_data.
>
> The userspace can use SNP_GET_REPORT ioctl() to query the guest
> attestation report.
>
> See SEV-SNP spec section Guest Messages for more details.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

Reviewed-by: Peter Gonda <pgonda@google.com>

I'll try and do some basic functionality testing done with this later.

> ---
> Documentation/virt/coco/sevguest.rst | 81 ++++
> drivers/virt/Kconfig | 3 +
> drivers/virt/Makefile | 1 +
> drivers/virt/coco/sevguest/Kconfig | 12 +
> drivers/virt/coco/sevguest/Makefile | 2 +
> drivers/virt/coco/sevguest/sevguest.c | 605 ++++++++++++++++++++++++++
> drivers/virt/coco/sevguest/sevguest.h | 98 +++++
> include/uapi/linux/sev-guest.h | 50 +++
> 8 files changed, 852 insertions(+)
> create mode 100644 Documentation/virt/coco/sevguest.rst
> create mode 100644 drivers/virt/coco/sevguest/Kconfig
> create mode 100644 drivers/virt/coco/sevguest/Makefile
> create mode 100644 drivers/virt/coco/sevguest/sevguest.c
> create mode 100644 drivers/virt/coco/sevguest/sevguest.h
> create mode 100644 include/uapi/linux/sev-guest.h
>
> diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst
> new file mode 100644
> index 000000000000..47ef3b0821d5
> --- /dev/null
> +++ b/Documentation/virt/coco/sevguest.rst
> @@ -0,0 +1,81 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===================================================================
> +The Definitive SEV Guest API Documentation
> +===================================================================
> +
> +1. General description
> +======================
> +
> +The SEV API is a set of ioctls that are used by the guest or hypervisor
> +to get or set certain aspect of the SEV virtual machine. The ioctls belong
> +to the following classes:
> +
> + - Hypervisor ioctls: These query and set global attributes which affect the
> + whole SEV firmware. These ioctl are used by platform provision tools.
> +
> + - Guest ioctls: These query and set attributes of the SEV virtual machine.
> +
> +2. API description
> +==================
> +
> +This section describes ioctls that can be used to query or set SEV guests.
> +For each ioctl, the following information is provided along with a
> +description:
> +
> + Technology:
> + which SEV technology provides this ioctl. sev, sev-es, sev-snp or all.
> +
> + Type:
> + hypervisor or guest. The ioctl can be used inside the guest or the
> + hypervisor.
> +
> + Parameters:
> + what parameters are accepted by the ioctl.
> +
> + Returns:
> + the return value. General error numbers (ENOMEM, EINVAL)
> + are not detailed, but errors with specific meanings are.
> +
> +The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
> +The ioctl accepts struct snp_user_guest_request. The input and output structure is
> +specified through the req_data and resp_data field respectively. If the ioctl fails
> +to execute due to a firmware error, then fw_err code will be set otherwise the
> +fw_err will be set to 0xff.
> +
> +::
> + struct snp_guest_request_ioctl {
> + /* Message version number */
> + __u32 msg_version;
> +
> + /* Request and response structure address */
> + __u64 req_data;
> + __u64 resp_data;
> +
> + /* firmware error code on failure (see psp-sev.h) */
> + __u64 fw_err;
> + };
> +
> +2.1 SNP_GET_REPORT
> +------------------
> +
> +:Technology: sev-snp
> +:Type: guest ioctl
> +:Parameters (in): struct snp_report_req
> +:Returns (out): struct snp_report_resp on success, -negative on error
> +
> +The SNP_GET_REPORT ioctl can be used to query the attestation report from the
> +SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command
> +provided by the SEV-SNP firmware to query the attestation report.
> +
> +On success, the snp_report_resp.data will contains the report. The report
> +contain the format described in the SEV-SNP specification. See the SEV-SNP
> +specification for further details.
> +
> +
> +Reference
> +---------
> +
> +SEV-SNP and GHCB specification: developer.amd.com/sev
> +
> +The driver is based on SEV-SNP firmware spec 0.9 and GHCB spec version 2.0.
> diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
> index 8061e8ef449f..e457e47610d3 100644
> --- a/drivers/virt/Kconfig
> +++ b/drivers/virt/Kconfig
> @@ -36,4 +36,7 @@ source "drivers/virt/vboxguest/Kconfig"
> source "drivers/virt/nitro_enclaves/Kconfig"
>
> source "drivers/virt/acrn/Kconfig"
> +
> +source "drivers/virt/coco/sevguest/Kconfig"
> +
> endif
> diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> index 3e272ea60cd9..9c704a6fdcda 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -8,3 +8,4 @@ obj-y += vboxguest/
>
> obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/
> obj-$(CONFIG_ACRN_HSM) += acrn/
> +obj-$(CONFIG_SEV_GUEST) += coco/sevguest/
> diff --git a/drivers/virt/coco/sevguest/Kconfig b/drivers/virt/coco/sevguest/Kconfig
> new file mode 100644
> index 000000000000..07ab9ec6471c
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/Kconfig
> @@ -0,0 +1,12 @@
> +config SEV_GUEST
> + tristate "AMD SEV Guest driver"
> + default y
> + depends on AMD_MEM_ENCRYPT && CRYPTO_AEAD2
> + help
> + SEV-SNP firmware provides the guest a mechanism to communicate with
> + the PSP without risk from a malicious hypervisor who wishes to read,
> + alter, drop or replay the messages sent. The driver provides
> + userspace interface to communicate with the PSP to request the
> + attestation report and more.
> +
> + If you choose 'M' here, this module will be called sevguest.
> diff --git a/drivers/virt/coco/sevguest/Makefile b/drivers/virt/coco/sevguest/Makefile
> new file mode 100644
> index 000000000000..b1ffb2b4177b
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/Makefile
> @@ -0,0 +1,2 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_SEV_GUEST) += sevguest.o
> diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c
> new file mode 100644
> index 000000000000..6dc0785ddd4b
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/sevguest.c
> @@ -0,0 +1,605 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * AMD Secure Encrypted Virtualization Nested Paging (SEV-SNP) guest request interface
> + *
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Brijesh Singh <brijesh.singh@amd.com>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <linux/mutex.h>
> +#include <linux/io.h>
> +#include <linux/platform_device.h>
> +#include <linux/miscdevice.h>
> +#include <linux/set_memory.h>
> +#include <linux/fs.h>
> +#include <crypto/aead.h>
> +#include <linux/scatterlist.h>
> +#include <linux/psp-sev.h>
> +#include <uapi/linux/sev-guest.h>
> +#include <uapi/linux/psp-sev.h>
> +
> +#include <asm/svm.h>
> +#include <asm/sev.h>
> +
> +#include "sevguest.h"
> +
> +#define DEVICE_NAME "sev-guest"
> +#define AAD_LEN 48
> +#define MSG_HDR_VER 1
> +
> +struct snp_guest_crypto {
> + struct crypto_aead *tfm;
> + u8 *iv, *authtag;
> + int iv_len, a_len;
> +};
> +
> +struct snp_guest_dev {
> + struct device *dev;
> + struct miscdevice misc;
> +
> + struct snp_guest_crypto *crypto;
> + struct snp_guest_msg *request, *response;
> + struct snp_secrets_page_layout *layout;
> + struct snp_req_data input;
> + u32 *os_area_msg_seqno;
> + u8 *vmpck;
> +};
> +
> +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 DEFINE_MUTEX(snp_cmd_mutex);
> +
> +static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
> +{
> + char zero_key[VMPCK_KEY_LEN] = {0};
> +
> + if (snp_dev->vmpck)
> + return memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN) == 0;
> +
> + return true;
> +}
> +
> +static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
> +{
> + 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_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_ratelimited("SNP guest 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;
> +
> + return container_of(dev, struct snp_guest_dev, misc);
> +}
> +
> +static struct snp_guest_crypto *init_crypto(struct snp_guest_dev *snp_dev, u8 *key, size_t keylen)
> +{
> + struct snp_guest_crypto *crypto;
> +
> + crypto = kzalloc(sizeof(*crypto), GFP_KERNEL_ACCOUNT);
> + if (!crypto)
> + return NULL;
> +
> + crypto->tfm = crypto_alloc_aead("gcm(aes)", 0, 0);
> + if (IS_ERR(crypto->tfm))
> + goto e_free;
> +
> + if (crypto_aead_setkey(crypto->tfm, key, keylen))
> + goto e_free_crypto;
> +
> + crypto->iv_len = crypto_aead_ivsize(crypto->tfm);
> + if (crypto->iv_len < 12) {
> + dev_err(snp_dev->dev, "IV length is less than 12.\n");
> + goto e_free_crypto;
> + }
> +
> + crypto->iv = kmalloc(crypto->iv_len, GFP_KERNEL_ACCOUNT);
> + if (!crypto->iv)
> + goto e_free_crypto;
> +
> + if (crypto_aead_authsize(crypto->tfm) > MAX_AUTHTAG_LEN) {
> + if (crypto_aead_setauthsize(crypto->tfm, MAX_AUTHTAG_LEN)) {
> + dev_err(snp_dev->dev, "failed to set authsize to %d\n", MAX_AUTHTAG_LEN);
> + goto e_free_crypto;
> + }
> + }
> +
> + crypto->a_len = crypto_aead_authsize(crypto->tfm);
> + crypto->authtag = kmalloc(crypto->a_len, GFP_KERNEL_ACCOUNT);
> + if (!crypto->authtag)
> + goto e_free_crypto;
> +
> + return crypto;
> +
> +e_free_crypto:
> + crypto_free_aead(crypto->tfm);
> +e_free:
> + kfree(crypto->iv);
> + kfree(crypto->authtag);
> + kfree(crypto);
> +
> + return NULL;
> +}
> +
> +static void deinit_crypto(struct snp_guest_crypto *crypto)
> +{
> + crypto_free_aead(crypto->tfm);
> + kfree(crypto->iv);
> + kfree(crypto->authtag);
> + kfree(crypto);
> +}
> +
> +static int enc_dec_message(struct snp_guest_crypto *crypto, struct snp_guest_msg *msg,
> + u8 *src_buf, u8 *dst_buf, size_t len, bool enc)
> +{
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> + struct scatterlist src[3], dst[3];
> + DECLARE_CRYPTO_WAIT(wait);
> + struct aead_request *req;
> + int ret;
> +
> + req = aead_request_alloc(crypto->tfm, GFP_KERNEL);
> + if (!req)
> + return -ENOMEM;
> +
> + /*
> + * AEAD memory operations:
> + * +------ AAD -------+------- DATA -----+---- AUTHTAG----+
> + * | msg header | plaintext | hdr->authtag |
> + * | bytes 30h - 5Fh | or | |
> + * | | cipher | |
> + * +------------------+------------------+----------------+
> + */
> + sg_init_table(src, 3);
> + sg_set_buf(&src[0], &hdr->algo, AAD_LEN);
> + sg_set_buf(&src[1], src_buf, hdr->msg_sz);
> + sg_set_buf(&src[2], hdr->authtag, crypto->a_len);
> +
> + sg_init_table(dst, 3);
> + sg_set_buf(&dst[0], &hdr->algo, AAD_LEN);
> + sg_set_buf(&dst[1], dst_buf, hdr->msg_sz);
> + sg_set_buf(&dst[2], hdr->authtag, crypto->a_len);
> +
> + aead_request_set_ad(req, AAD_LEN);
> + aead_request_set_tfm(req, crypto->tfm);
> + aead_request_set_callback(req, 0, crypto_req_done, &wait);
> +
> + aead_request_set_crypt(req, src, dst, len, crypto->iv);
> + ret = crypto_wait_req(enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req), &wait);
> +
> + aead_request_free(req);
> + return ret;
> +}
> +
> +static int __enc_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
> + void *plaintext, size_t len)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> +
> + memset(crypto->iv, 0, crypto->iv_len);
> + memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> +
> + return enc_dec_message(crypto, msg, plaintext, msg->payload, len, true);
> +}
> +
> +static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
> + void *plaintext, size_t len)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> +
> + /* Build IV with response buffer sequence number */
> + memset(crypto->iv, 0, crypto->iv_len);
> + memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> +
> + return enc_dec_message(crypto, msg, msg->payload, plaintext, len, false);
> +}
> +
> +static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + 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;
> +
> + dev_dbg(snp_dev->dev, "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 + crypto->a_len) > sz))
> + return -EBADMSG;
> +
> + /* Decrypt the payload */
> + return dec_payload(snp_dev, resp, payload, resp_hdr->msg_sz + crypto->a_len);
> +}
> +
> +static bool enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
> + void *payload, size_t sz)
> +{
> + struct snp_guest_msg *req = snp_dev->request;
> + struct snp_guest_msg_hdr *hdr = &req->hdr;
> +
> + memset(req, 0, sizeof(*req));
> +
> + 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_seqno = seqno;
> + hdr->msg_vmpck = vmpck_id;
> + hdr->msg_sz = sz;
> +
> + /* Verify the sequence number is non-zero */
> + if (!hdr->msg_seqno)
> + return -ENOSR;
> +
> + dev_dbg(snp_dev->dev, "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, req, payload, sz);
> +}
> +
> +static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
> + u8 type, void *req_buf, size_t req_sz, void *resp_buf,
> + u32 resp_sz, __u64 *fw_err)
> +{
> + unsigned long err;
> + 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;
> +
> + memset(snp_dev->response, 0, sizeof(*snp_dev->response));
> +
> + /* Encrypt the userspace provided payload */
> + rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
> + if (rc)
> + return rc;
> +
> + /* Call firmware to process the request */
> + rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
> + if (fw_err)
> + *fw_err = err;

All the other pointers are required. Why not require this one to make
it simpler?

> +
> + if (rc)
> + return rc;
> +
> + rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
> + if (rc) {
> + /*
> + * The verify_and_dec_payload() will fail only if the hypervisor is
> + * actively modifying the message header or corrupting the encrypted payload.
> + * This hints that hypervisor is acting in a bad faith. Disable the VMPCK so that
> + * the key cannot be used for any communication. The key is disabled to ensure
> + * that AES-GCM does not use the same IV while encrypting the request payload.
> + */
> + dev_alert(snp_dev->dev,
> + "Detected unexpected decode failure, disabling the vmpck_id %d\n",
> + vmpck_id);
> + snp_disable_vmpck(snp_dev);
> + return rc;
> + }
> +
> + /* Increment to new message sequence after payload decryption was successful. */
> + snp_inc_msg_seqno(snp_dev);
> +
> + return 0;
> +}
> +
> +static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + struct snp_report_req req = {0};
> + struct snp_report_resp *resp;
> + int rc, resp_len;
> +
> + if (!arg->req_data || !arg->resp_data)
> + return -EINVAL;
> +
> + /* Copy the request payload from userspace */
> + if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
> + return -EFAULT;
> +
> + /*
> + * The intermediate response buffer is used while decrypting the
> + * response payload. Make sure that it has enough space to cover the
> + * authtag.
> + */
> + resp_len = sizeof(resp->data) + crypto->a_len;
> + resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
> + if (!resp)
> + return -ENOMEM;
> +
> + /* Issue the command to get the attestation report */
> + rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
> + SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
> + resp_len, &arg->fw_err);
> + if (rc)
> + goto e_free;
> +
> + /* Copy the response payload to userspace */
> + if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
> + rc = -EFAULT;
> +
> +e_free:
> + kfree(resp);
> + return rc;
> +}
> +
> +static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
> +{
> + struct snp_guest_dev *snp_dev = to_snp_dev(file);
> + void __user *argp = (void __user *)arg;
> + struct snp_guest_request_ioctl input;
> + int ret = -ENOTTY;
> +
> + if (copy_from_user(&input, argp, sizeof(input)))
> + return -EFAULT;
> +
> + input.fw_err = 0xff;
> +
> + /* Message version must be non-zero */
> + if (!input.msg_version)
> + return -EINVAL;
> +
> + mutex_lock(&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");
> + mutex_unlock(&snp_cmd_mutex);
> + return -ENOTTY;
> + }
> +
> + switch (ioctl) {
> + case SNP_GET_REPORT:
> + ret = get_report(snp_dev, &input);
> + break;
> + default:
> + break;
> + }
> +
> + mutex_unlock(&snp_cmd_mutex);
> +
> + if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
> + return -EFAULT;
> +
> + return ret;
> +}
> +
> +static void free_shared_pages(void *buf, size_t sz)
> +{
> + unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> +
> + if (!buf)
> + return;
> +
> + /* If fail to restore the encryption mask then leak it. */
> + if (WARN_ONCE(set_memory_encrypted((unsigned long)buf, npages),
> + "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 (IS_ERR(page))
> + return NULL;
> +
> + ret = set_memory_decrypted((unsigned long)page_address(page), npages);
> + if (ret) {
> + pr_err("SEV-SNP: 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,
> +};
> +
> +static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
> +{
> + u8 *key = NULL;
> +
> + switch (id) {
> + case 0:
> + *seqno = &layout->os_area.msg_seqno_0;
> + key = layout->vmpck0;
> + break;
> + case 1:
> + *seqno = &layout->os_area.msg_seqno_1;
> + key = layout->vmpck1;
> + break;
> + case 2:
> + *seqno = &layout->os_area.msg_seqno_2;
> + key = layout->vmpck2;
> + break;
> + case 3:
> + *seqno = &layout->os_area.msg_seqno_3;
> + key = layout->vmpck3;
> + break;
> + default:
> + break;
> + }
> +
> + return key;
> +}
> +
> +static int __init snp_guest_probe(struct platform_device *pdev)
> +{
> + struct snp_secrets_page_layout *layout;
> + struct snp_guest_platform_data *data;
> + struct device *dev = &pdev->dev;
> + struct snp_guest_dev *snp_dev;
> + struct miscdevice *misc;
> + int ret;
> +
> + if (!dev->platform_data)
> + return -ENODEV;
> +
> + data = (struct snp_guest_platform_data *)dev->platform_data;
> + layout = (__force void *)ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
> + if (!layout)
> + return -ENODEV;
> +
> + ret = -ENOMEM;
> + snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
> + if (!snp_dev)
> + goto e_fail;
> +
> + ret = -EINVAL;
> + snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
> + if (!snp_dev->vmpck) {
> + dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
> + goto e_fail;
> + }
> +
> + /* Verify that VMPCK is not zero. */
> + if (is_vmpck_empty(snp_dev)) {
> + dev_err(dev, "vmpck id %d is null\n", vmpck_id);
> + goto e_fail;
> + }
> +
> + platform_set_drvdata(pdev, snp_dev);
> + snp_dev->dev = dev;
> + snp_dev->layout = layout;
> +
> + /* Allocate the shared page used for the request and response message. */
> + snp_dev->request = alloc_shared_pages(sizeof(struct snp_guest_msg));
> + if (!snp_dev->request)
> + goto e_fail;
> +
> + snp_dev->response = alloc_shared_pages(sizeof(struct snp_guest_msg));
> + if (!snp_dev->response)
> + goto e_fail;
> +
> + ret = -EIO;
> + snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN);
> + if (!snp_dev->crypto)
> + goto e_fail;
> +
> + 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_fail;
> +
> + dev_info(dev, "Initialized SEV-SNP guest driver (using vmpck_id %d)\n", vmpck_id);
> + return 0;
> +
> +e_fail:
> + iounmap(layout);
> + free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
> + free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
> +
> + return ret;
> +}
> +
> +static int __exit snp_guest_remove(struct platform_device *pdev)
> +{
> + struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
> +
> + free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
> + free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
> + deinit_crypto(snp_dev->crypto);
> + misc_deregister(&snp_dev->misc);
> +
> + return 0;
> +}
> +
> +static struct platform_driver snp_guest_driver = {
> + .remove = __exit_p(snp_guest_remove),
> + .driver = {
> + .name = "snp-guest",
> + },
> +};
> +
> +module_platform_driver_probe(snp_guest_driver, snp_guest_probe);
> +
> +MODULE_AUTHOR("Brijesh Singh <brijesh.singh@amd.com>");
> +MODULE_LICENSE("GPL");
> +MODULE_VERSION("1.0.0");
> +MODULE_DESCRIPTION("AMD SNP Guest Driver");
> diff --git a/drivers/virt/coco/sevguest/sevguest.h b/drivers/virt/coco/sevguest/sevguest.h
> new file mode 100644
> index 000000000000..cfa76cf8a21a
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/sevguest.h
> @@ -0,0 +1,98 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Brijesh Singh <brijesh.singh@amd.com>
> + *
> + * SEV-SNP API spec is available at https://developer.amd.com/sev
> + */
> +
> +#ifndef __LINUX_SEVGUEST_H_
> +#define __LINUX_SEVGUEST_H_
> +
> +#include <linux/types.h>
> +
> +#define MAX_AUTHTAG_LEN 32
> +
> +/* See SNP spec SNP_GUEST_REQUEST section for the structure */
> +enum msg_type {
> + SNP_MSG_TYPE_INVALID = 0,
> + SNP_MSG_CPUID_REQ,
> + SNP_MSG_CPUID_RSP,
> + SNP_MSG_KEY_REQ,
> + SNP_MSG_KEY_RSP,
> + SNP_MSG_REPORT_REQ,
> + SNP_MSG_REPORT_RSP,
> + SNP_MSG_EXPORT_REQ,
> + SNP_MSG_EXPORT_RSP,
> + SNP_MSG_IMPORT_REQ,
> + SNP_MSG_IMPORT_RSP,
> + SNP_MSG_ABSORB_REQ,
> + SNP_MSG_ABSORB_RSP,
> + SNP_MSG_VMRK_REQ,
> + SNP_MSG_VMRK_RSP,
> +
> + SNP_MSG_TYPE_MAX
> +};
> +
> +enum aead_algo {
> + SNP_AEAD_INVALID,
> + SNP_AEAD_AES_256_GCM,
> +};
> +
> +struct snp_guest_msg_hdr {
> + u8 authtag[MAX_AUTHTAG_LEN];
> + u64 msg_seqno;
> + u8 rsvd1[8];
> + u8 algo;
> + u8 hdr_version;
> + u16 hdr_sz;
> + u8 msg_type;
> + u8 msg_version;
> + u16 msg_sz;
> + u32 rsvd2;
> + u8 msg_vmpck;
> + u8 rsvd3[35];
> +} __packed;
> +
> +struct snp_guest_msg {
> + struct snp_guest_msg_hdr hdr;
> + u8 payload[4000];
> +} __packed;
> +
> +/*
> + * 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
> + * number for each VMPCK.
> + *
> + * See the GHCB spec section Secret page layout for the format for this area.
> + */
> +struct secrets_os_area {
> + u32 msg_seqno_0;
> + u32 msg_seqno_1;
> + u32 msg_seqno_2;
> + u32 msg_seqno_3;
> + u64 ap_jump_table_pa;
> + u8 rsvd[40];
> + u8 guest_usage[32];
> +} __packed;
> +
> +#define VMPCK_KEY_LEN 32
> +
> +/* See the SNP spec version 0.9 for secrets page format */
> +struct snp_secrets_page_layout {
> + u32 version;
> + u32 imien : 1,
> + rsvd1 : 31;
> + u32 fms;
> + u32 rsvd2;
> + u8 gosvw[16];
> + u8 vmpck0[VMPCK_KEY_LEN];
> + u8 vmpck1[VMPCK_KEY_LEN];
> + u8 vmpck2[VMPCK_KEY_LEN];
> + u8 vmpck3[VMPCK_KEY_LEN];
> + struct secrets_os_area os_area;
> + u8 rsvd3[3840];
> +} __packed;
> +
> +#endif /* __LINUX_SNP_GUEST_H__ */
> diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h
> new file mode 100644
> index 000000000000..081d314a6279
> --- /dev/null
> +++ b/include/uapi/linux/sev-guest.h
> @@ -0,0 +1,50 @@
> +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
> +/*
> + * Userspace interface for AMD SEV and SEV-SNP guest driver.
> + *
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Brijesh Singh <brijesh.singh@amd.com>
> + *
> + * SEV API specification is available at: https://developer.amd.com/sev/
> + */
> +
> +#ifndef __UAPI_LINUX_SEV_GUEST_H_
> +#define __UAPI_LINUX_SEV_GUEST_H_
> +
> +#include <linux/types.h>
> +
> +struct snp_report_req {
> + /* user data that should be included in the report */
> + __u8 user_data[64];
> +
> + /* The vmpl level to be included in the report */
> + __u32 vmpl;
> +
> + /* Must be zero filled */
> + __u8 rsvd[28];
> +};
> +
> +struct snp_report_resp {
> + /* response data, see SEV-SNP spec for the format */
> + __u8 data[4000];
> +};
> +
> +struct snp_guest_request_ioctl {
> + /* message version number (must be non-zero) */
> + __u8 msg_version;
> +
> + /* Request and response structure address */
> + __u64 req_data;
> + __u64 resp_data;
> +
> + /* firmware error code on failure (see psp-sev.h) */
> + __u64 fw_err;
> +};
> +
> +#define SNP_GUEST_REQ_IOC_TYPE 'S'
> +
> +/* Get SNP attestation report */
> +#define SNP_GET_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x0, struct snp_guest_request_ioctl)
> +
> +#endif /* __UAPI_LINUX_SEV_GUEST_H_ */
> --
> 2.25.1
>