On Wed, Dec 14, 2022 at 11:54 AM Michael Roth <michael.roth@xxxxxxx> wrote:
>
> From: Brijesh Singh <brijesh.singh@xxxxxxx>
>
> The behavior of the SEV-legacy commands is altered when the SNP firmware
> is in the INIT state. When SNP is in INIT state, all the SEV-legacy
> commands that cause the firmware to write to memory must be in the
> firmware state before issuing the command..
>
> A command buffer may contains a system physical address that the firmware
> may write to. There are two cases that need to be handled:
>
> 1) system physical address points to a guest memory
> 2) system physical address points to a host memory
>
> To handle the case #1, change the page state to the firmware in the RMP
> table before issuing the command and restore the state to shared after the
> command completes.
>
> For the case #2, use a bounce buffer to complete the request.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
> Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> ---
> drivers/crypto/ccp/sev-dev.c | 370 ++++++++++++++++++++++++++++++++++-
> drivers/crypto/ccp/sev-dev.h | 12 ++
> 2 files changed, 372 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 4c12e98a1219..5eb2e8f364d4 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -286,6 +286,30 @@ static int rmp_mark_pages_firmware(unsigned long paddr, unsigned int npages, boo
> return rc;
> }
>
> +static int rmp_mark_pages_shared(unsigned long paddr, unsigned int npages)
> +{
> + /* Cbit maybe set in the paddr */
> + unsigned long pfn = __sme_clr(paddr) >> PAGE_SHIFT;
> + int rc, n = 0, i;
> +
> + for (i = 0; i < npages; i++, pfn++, n++) {
> + rc = rmp_make_shared(pfn, PG_LEVEL_4K);
> + if (rc)
> + goto cleanup;
> + }
> +
> + return 0;
> +
> +cleanup:
> + /*
> + * If failed to change the page state to shared, then its not safe
> + * to release the page back to the system, leak it.
> + */
> + snp_mark_pages_offline(pfn, npages - n);
> +
> + return rc;
> +}
> +
> static struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order, bool locked)
> {
> unsigned long npages = 1ul << order, paddr;
> @@ -487,12 +511,295 @@ static int sev_write_init_ex_file_if_required(int cmd_id)
> return sev_write_init_ex_file();
> }
>
> +static int alloc_snp_host_map(struct sev_device *sev)
> +{
> + struct page *page;
> + int i;
> +
> + for (i = 0; i < MAX_SNP_HOST_MAP_BUFS; i++) {
> + struct snp_host_map *map = &sev->snp_host_map[i];
> +
> + memset(map, 0, sizeof(*map));
> +
> + page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(SEV_FW_BLOB_MAX_SIZE));
> + if (!page)
> + return -ENOMEM;
> +
> + map->host = page_address(page);
> + }
> +
> + return 0;
> +}
> +
> +static void free_snp_host_map(struct sev_device *sev)
> +{
> + int i;
> +
> + for (i = 0; i < MAX_SNP_HOST_MAP_BUFS; i++) {
> + struct snp_host_map *map = &sev->snp_host_map[i];
> +
> + if (map->host) {
> + __free_pages(virt_to_page(map->host), get_order(SEV_FW_BLOB_MAX_SIZE));
> + memset(map, 0, sizeof(*map));
> + }
> + }
> +}
> +
> +static int map_firmware_writeable(u64 *paddr, u32 len, bool guest, struct snp_host_map *map)
> +{
> + unsigned int npages = PAGE_ALIGN(len) >> PAGE_SHIFT;
> +
> + map->active = false;
> +
> + if (!paddr || !len)
> + return 0;
> +
> + map->paddr = *paddr;
> + map->len = len;
> +
> + /* If paddr points to a guest memory then change the page state to firmwware. */
> + if (guest) {
> + if (rmp_mark_pages_firmware(*paddr, npages, true))
> + return -EFAULT;
> +
> + goto done;
> + }
> +
> + if (!map->host)
> + return -ENOMEM;
> +
> + /* Check if the pre-allocated buffer can be used to fullfil the request. */
> + if (len > SEV_FW_BLOB_MAX_SIZE)
> + return -EINVAL;
> +
> + /* Transition the pre-allocated buffer to the firmware state. */
> + if (rmp_mark_pages_firmware(__pa(map->host), npages, true))
> + return -EFAULT;
> +
> + /* Set the paddr to use pre-allocated firmware buffer */
> + *paddr = __psp_pa(map->host);
> +
> +done:
> + map->active = true;
> + return 0;
> +}
> +
> +static int unmap_firmware_writeable(u64 *paddr, u32 len, bool guest, struct snp_host_map *map)
> +{
> + unsigned int npages = PAGE_ALIGN(len) >> PAGE_SHIFT;
> +
> + if (!map->active)
> + return 0;
> +
> + /* If paddr points to a guest memory then restore the page state to hypervisor. */
> + if (guest) {
> + if (snp_reclaim_pages(*paddr, npages, true))
> + return -EFAULT;
> +
> + goto done;
> + }
> +
> + /*
> + * Transition the pre-allocated buffer to hypervisor state before the access.
> + *
> + * This is because while changing the page state to firmware, the kernel unmaps
> + * the pages from the direct map, and to restore the direct map the pages must
> + * be transitioned back to the shared state.
> + */
> + if (snp_reclaim_pages(__pa(map->host), npages, true))
> + return -EFAULT;
> +
> + /* Copy the response data firmware buffer to the callers buffer. */
> + memcpy(__va(__sme_clr(map->paddr)), map->host, min_t(size_t, len, map->len));
> + *paddr = map->paddr;
> +
> +done:
> + map->active = false;
> + return 0;
> +}
> +
> +static bool sev_legacy_cmd_buf_writable(int cmd)
> +{
> + switch (cmd) {
> + case SEV_CMD_PLATFORM_STATUS:
> + case SEV_CMD_GUEST_STATUS:
> + case SEV_CMD_LAUNCH_START:
> + case SEV_CMD_RECEIVE_START:
> + case SEV_CMD_LAUNCH_MEASURE:
> + case SEV_CMD_SEND_START:
> + case SEV_CMD_SEND_UPDATE_DATA:
> + case SEV_CMD_SEND_UPDATE_VMSA:
> + case SEV_CMD_PEK_CSR:
> + case SEV_CMD_PDH_CERT_EXPORT:
> + case SEV_CMD_GET_ID:
> + case SEV_CMD_ATTESTATION_REPORT:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> +#define prep_buffer(name, addr, len, guest, map) \
> + func(&((typeof(name *))cmd_buf)->addr, ((typeof(name *))cmd_buf)->len, guest, map)
> +
> +static int __snp_cmd_buf_copy(int cmd, void *cmd_buf, bool to_fw, int fw_err)
> +{
> + int (*func)(u64 *paddr, u32 len, bool guest, struct snp_host_map *map);
> + struct sev_device *sev = psp_master->sev_data;
> + bool from_fw = !to_fw;
> +
> + /*
> + * After the command is completed, change the command buffer memory to
> + * hypervisor state.
> + *
> + * The immutable bit is automatically cleared by the firmware, so
> + * no not need to reclaim the page.
> + */
> + if (from_fw && sev_legacy_cmd_buf_writable(cmd)) {
> + if (rmp_mark_pages_shared(__pa(cmd_buf), 1))
> + return -EFAULT;
If we return here, we will skip calling unmap_firmware_writeable and
we will leak some pages in firmware state.
> +
> + /* No need to go further if firmware failed to execute command. */
> + if (fw_err)
> + return 0;
> + }
> +
> + if (to_fw)
> + func = map_firmware_writeable;
> + else
> + func = unmap_firmware_writeable;
> +
> + /*
> + * A command buffer may contains a system physical address. If the address
> + * points to a host memory then use an intermediate firmware page otherwise
> + * change the page state in the RMP table.
> + */
> + switch (cmd) {
> + case SEV_CMD_PDH_CERT_EXPORT:
> + if (prep_buffer(struct sev_data_pdh_cert_export, pdh_cert_address,
> + pdh_cert_len, false, &sev->snp_host_map[0]))
> + goto err;
> + if (prep_buffer(struct sev_data_pdh_cert_export, cert_chain_address,
> + cert_chain_len, false, &sev->snp_host_map[1]))
> + goto err;
> + break;
> + case SEV_CMD_GET_ID:
> + if (prep_buffer(struct sev_data_get_id, address, len,
> + false, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_PEK_CSR:
> + if (prep_buffer(struct sev_data_pek_csr, address, len,
> + false, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_LAUNCH_UPDATE_DATA:
> + if (prep_buffer(struct sev_data_launch_update_data, address, len,
> + true, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_LAUNCH_UPDATE_VMSA:
> + if (prep_buffer(struct sev_data_launch_update_vmsa, address, len,
> + true, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_LAUNCH_MEASURE:
> + if (prep_buffer(struct sev_data_launch_measure, address, len,
> + false, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_LAUNCH_UPDATE_SECRET:
> + if (prep_buffer(struct sev_data_launch_secret, guest_address, guest_len,
> + true, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_DBG_DECRYPT:
> + if (prep_buffer(struct sev_data_dbg, dst_addr, len, false,
> + &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_DBG_ENCRYPT:
> + if (prep_buffer(struct sev_data_dbg, dst_addr, len, true,
> + &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_ATTESTATION_REPORT:
> + if (prep_buffer(struct sev_data_attestation_report, address, len,
> + false, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_SEND_START:
> + if (prep_buffer(struct sev_data_send_start, session_address,
> + session_len, false, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_SEND_UPDATE_DATA:
> + if (prep_buffer(struct sev_data_send_update_data, hdr_address, hdr_len,
> + false, &sev->snp_host_map[0]))
> + goto err;
> + if (prep_buffer(struct sev_data_send_update_data, trans_address,
> + trans_len, false, &sev->snp_host_map[1]))
> + goto err;
> + break;
> + case SEV_CMD_SEND_UPDATE_VMSA:
> + if (prep_buffer(struct sev_data_send_update_vmsa, hdr_address, hdr_len,
> + false, &sev->snp_host_map[0]))
> + goto err;
> + if (prep_buffer(struct sev_data_send_update_vmsa, trans_address,
> + trans_len, false, &sev->snp_host_map[1]))
> + goto err;
> + break;
> + case SEV_CMD_RECEIVE_UPDATE_DATA:
> + if (prep_buffer(struct sev_data_receive_update_data, guest_address,
> + guest_len, true, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + case SEV_CMD_RECEIVE_UPDATE_VMSA:
> + if (prep_buffer(struct sev_data_receive_update_vmsa, guest_address,
> + guest_len, true, &sev->snp_host_map[0]))
> + goto err;
> + break;
> + default:
> + break;
> + }
> +
> + /* The command buffer need to be in the firmware state. */
> + if (to_fw && sev_legacy_cmd_buf_writable(cmd)) {
> + if (rmp_mark_pages_firmware(__pa(cmd_buf), 1, true))
> + return -EFAULT;
This function moves two separate pages to firmware state. First
calling map_firmware_writeable and second calling
rmp_mark_pages_firmware for cmd_buf.
In case rmp_mark_pages_firmware fails for cmd_buf, the page which has
already moved to firmware state in map_firmware_writeable should be
reclaimed.
This is a problem especially if we leak a guest owned page in firmware
state. Since this is used only by legacy SEV VMs, these leaked pages
will never be reclaimed back when destroying these VMs.
>
> + }
> +
> + return 0;
> +
> +err:
> + return -EINVAL;
> +}
> +
> +static inline bool need_firmware_copy(int cmd)
> +{
> + struct sev_device *sev = psp_master->sev_data;
> +
> + /* After SNP is INIT'ed, the behavior of legacy SEV command is changed. */
> + return ((cmd < SEV_CMD_SNP_INIT) && sev->snp_initialized) ? true : false;
> +}
> +
> +static int snp_aware_copy_to_firmware(int cmd, void *data)
> +{
> + return __snp_cmd_buf_copy(cmd, data, true, 0);
> +}
> +
> +static int snp_aware_copy_from_firmware(int cmd, void *data, int fw_err)
> +{
> + return __snp_cmd_buf_copy(cmd, data, false, fw_err);
> +}
> +
> static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
> {
> struct psp_device *psp = psp_master;
> struct sev_device *sev;
> unsigned int phys_lsb, phys_msb;
> unsigned int reg, ret = 0;
> + void *cmd_buf;
> int buf_len;
>
> if (!psp || !psp->sev_data)
> @@ -512,12 +819,28 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
> * work for some memory, e.g. vmalloc'd addresses, and @data may not be
> * physically contiguous.
> */
> - if (data)
> - memcpy(sev->cmd_buf, data, buf_len);
> + if (data) {
> + if (sev->cmd_buf_active > 2)
> + return -EBUSY;
> +
> + cmd_buf = sev->cmd_buf_active ? sev->cmd_buf_backup : sev->cmd_buf;
> +
> + memcpy(cmd_buf, data, buf_len);
> + sev->cmd_buf_active++;
> +
> + /*
> + * The behavior of the SEV-legacy commands is altered when the
> + * SNP firmware is in the INIT state.
> + */
> + if (need_firmware_copy(cmd) && snp_aware_copy_to_firmware(cmd, sev->cmd_buf))
> + return -EFAULT;
> + } else {
> + cmd_buf = sev->cmd_buf;
> + }
>
> /* Get the physical address of the command buffer */
> - phys_lsb = data ? lower_32_bits(__psp_pa(sev->cmd_buf)) : 0;
> - phys_msb = data ? upper_32_bits(__psp_pa(sev->cmd_buf)) : 0;
> + phys_lsb = data ? lower_32_bits(__psp_pa(cmd_buf)) : 0;
> + phys_msb = data ? upper_32_bits(__psp_pa(cmd_buf)) : 0;
>
> dev_dbg(sev->dev, "sev command id %#x buffer 0x%08x%08x timeout %us\n",
> cmd, phys_msb, phys_lsb, psp_timeout);
> @@ -560,15 +883,24 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
> ret = sev_write_init_ex_file_if_required(cmd);
> }
>
> - print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
> - buf_len, false);
> -
> /*
> * Copy potential output from the PSP back to data. Do this even on
> * failure in case the caller wants to glean something from the error.
> */
> - if (data)
> - memcpy(data, sev->cmd_buf, buf_len);
> + if (data) {
> + /*
> + * Restore the page state after the command completes.
> + */
> + if (need_firmware_copy(cmd) &&
> + snp_aware_copy_from_firmware(cmd, cmd_buf, ret))
> + return -EFAULT;
> +
> + memcpy(data, cmd_buf, buf_len);
> + sev->cmd_buf_active--;
> + }
> +
> + print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
> + buf_len, false);
>
> return ret;
> }
> @@ -1579,10 +1911,12 @@ int sev_dev_init(struct psp_device *psp)
> if (!sev)
> goto e_err;
>
> - sev->cmd_buf = (void *)devm_get_free_pages(dev, GFP_KERNEL, 0);
> + sev->cmd_buf = (void *)devm_get_free_pages(dev, GFP_KERNEL, 1);
> if (!sev->cmd_buf)
> goto e_sev;
>
> + sev->cmd_buf_backup = (uint8_t *)sev->cmd_buf + PAGE_SIZE;
> +
> psp->sev_data = sev;
>
> sev->dev = dev;
> @@ -1648,6 +1982,12 @@ static void sev_firmware_shutdown(struct sev_device *sev)
> snp_range_list = NULL;
> }
>
> + /*
> + * The host map need to clear the immutable bit so it must be free'd before the
> + * SNP firmware shutdown.
> + */
> + free_snp_host_map(sev);
> +
> sev_snp_shutdown(&error);
> }
>
> @@ -1722,6 +2062,14 @@ void sev_pci_init(void)
> dev_err(sev->dev, "SEV-SNP: failed to INIT error %#x\n", error);
> }
> }
> +
> + /*
> + * Allocate the intermediate buffers used for the legacy command handling.
> + */
> + if (alloc_snp_host_map(sev)) {
> + dev_notice(sev->dev, "Failed to alloc host map (disabling legacy SEV)\n");
> + goto skip_legacy;
> + }
> }
>
> /* Obtain the TMR memory area for SEV-ES use */
> @@ -1739,12 +2087,14 @@ void sev_pci_init(void)
> dev_err(sev->dev, "SEV: failed to INIT error %#x, rc %d\n",
> error, rc);
>
> +skip_legacy:
> dev_info(sev->dev, "SEV%s API:%d.%d build:%d\n", sev->snp_initialized ?
> "-SNP" : "", sev->api_major, sev->api_minor, sev->build);
>
> return;
>
> err:
> + free_snp_host_map(sev);
> psp_master->sev_data = NULL;
> }
>
> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
> index 34767657beb5..19d79f9d4212 100644
> --- a/drivers/crypto/ccp/sev-dev.h
> +++ b/drivers/crypto/ccp/sev-dev.h
> @@ -29,11 +29,20 @@
> #define SEV_CMDRESP_CMD_SHIFT 16
> #define SEV_CMDRESP_IOC BIT(0)
>
> +#define MAX_SNP_HOST_MAP_BUFS 2
> +
> struct sev_misc_dev {
> struct kref refcount;
> struct miscdevice misc;
> };
>
> +struct snp_host_map {
> + u64 paddr;
> + u32 len;
> + void *host;
> + bool active;
> +};
> +
> struct sev_device {
> struct device *dev;
> struct psp_device *psp;
> @@ -52,8 +61,11 @@ struct sev_device {
> u8 build;
>
> void *cmd_buf;
> + void *cmd_buf_backup;
> + int cmd_buf_active;
>
> bool snp_initialized;
> + struct snp_host_map snp_host_map[MAX_SNP_HOST_MAP_BUFS];
> };
>
> int sev_dev_init(struct psp_device *psp);
> --
> 2.25.1
>
