Messages in this thread | | | Date | Fri, 13 Jan 2023 16:03:52 -0600 | Subject | Re: [PATCH RFC v7 29/64] crypto: ccp: Handle the legacy SEV command when SNP is enabled | From | "Kalra, Ashish" <> |
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Hello Alper,
On 1/12/2023 2:47 PM, Alper Gun wrote: > On Wed, Dec 14, 2022 at 11:54 AM Michael Roth <michael.roth@amd.com> wrote: >> >> From: Brijesh Singh <brijesh.singh@amd.com> >> >> 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@amd.com> >> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> >> Signed-off-by: Michael Roth <michael.roth@amd.com> >> --- >> 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.
Do you mean those (guest) pages which were transitioned to firmware state as part of snp_aware_copy_to_firmware()->_snp_cmd_buf_copy()->map_firmware_writeable()?
> >> + >> + /* 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. >
Yes, this looks to be an inherent issue with the original patch, as you mentioned there are two pages - guest owned page and the HV cmd_buf, and failure to transition the cmd_buf back to HV/shared state has no corresponding recovery/reclaim for the transitioned guest page.
Thanks, Ashish
>> >> + } >> + >> + 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 >>
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