On 2/23/23 00:38, Zhi Wang wrote:
On Wed, 22 Feb 2023 16:43:54 -0600 "Kalra, Ashish" <ashish.kalra@xxxxxxx> wrote:On 2/22/2023 6:32 AM, Zhi Wang wrote:On Mon, 20 Feb 2023 12:38:18 -0600 Michael Roth <michael.roth@xxxxxxx> wrote:From: Brijesh Singh <brijesh.singh@xxxxxxx> The SEV-SNP firmware provides the SNP_CONFIG command used to set the system-wide configuration value for SNP guests. The information includes the TCB version string to be reported in guest attestation reports. Version 2 of the GHCB specification adds an NAE (SNP extended guest request) that a guest can use to query the reports that include additional certificates. In both cases, userspace provided additional data is included in the attestation reports. The userspace will use the SNP_SET_EXT_CONFIG command to give the certificate blob and the reported TCB version string at once. Note that the specification defines certificate blob with a specific GUID format; the userspace is responsible for building the proper certificate blob. The ioctl treats it an opaque blob. While it is not defined in the spec, but let's add SNP_GET_EXT_CONFIG command that can be used to obtain the data programmed through the SNP_SET_EXT_CONFIG. Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx> Signed-off-by: Michael Roth <michael.roth@xxxxxxx> --- Documentation/virt/coco/sev-guest.rst | 27 ++++++ drivers/crypto/ccp/sev-dev.c | 123 ++++++++++++++++++++++++++ drivers/crypto/ccp/sev-dev.h | 4 + include/uapi/linux/psp-sev.h | 17 ++++ 4 files changed, 171 insertions(+) diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst index 11ea67c944df..6cad4226c348 100644 --- a/Documentation/virt/coco/sev-guest.rst +++ b/Documentation/virt/coco/sev-guest.rst @@ -145,6 +145,33 @@ The SNP_PLATFORM_STATUS command is used to query the SNP platform status. The status includes API major, minor version and more. See the SEV-SNP specification for further details.+2.5 SNP_SET_EXT_CONFIG+---------------------- +:Technology: sev-snp +:Type: hypervisor ioctl cmd +:Parameters (in): struct sev_data_snp_ext_config +:Returns (out): 0 on success, -negative on error + +The SNP_SET_EXT_CONFIG is used to set the system-wide configuration such as +reported TCB version in the attestation report. The command is similar to +SNP_CONFIG command defined in the SEV-SNP spec. The main difference is the +command also accepts an additional certificate blob defined in the GHCB +specification. + +If the certs_address is zero, then the previous certificate blob will deleted. +For more information on the certificate blob layout, see the GHCB spec +(extended guest request message). + +2.6 SNP_GET_EXT_CONFIG +---------------------- +:Technology: sev-snp +:Type: hypervisor ioctl cmd +:Parameters (in): struct sev_data_snp_ext_config +:Returns (out): 0 on success, -negative on error + +The SNP_GET_EXT_CONFIG is used to query the system-wide configuration set +through the SNP_SET_EXT_CONFIG. + 3. SEV-SNP CPUID Enforcement ============================diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.cindex 65e13a562f3b..b56b00ca2cd4 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -1481,6 +1481,10 @@ static int __sev_snp_shutdown_locked(int *error) data.length = sizeof(data); data.iommu_snp_shutdown = 1;+ /* Free the memory used for caching the certificate data */+ kfree(sev->snp_certs_data); + sev->snp_certs_data = NULL; + wbinvd_on_all_cpus();retry:@@ -1793,6 +1797,118 @@ static int sev_ioctl_snp_platform_status(struct sev_issue_cmd *argp) return ret; }+static int sev_ioctl_snp_get_config(struct sev_issue_cmd *argp)+{ + struct sev_device *sev = psp_master->sev_data; + struct sev_user_data_ext_snp_config input; + int ret; + + if (!sev->snp_initialized || !argp->data) + return -EINVAL; + + memset(&input, 0, sizeof(input)); + + if (copy_from_user(&input, (void __user *)argp->data, sizeof(input))) + return -EFAULT; + + /* Copy the TCB version programmed through the SET_CONFIG to userspace */ + if (input.config_address) { + if (copy_to_user((void * __user)input.config_address, + &sev->snp_config, sizeof(struct sev_user_data_snp_config))) + return -EFAULT; + } + + /* Copy the extended certs programmed through the SNP_SET_CONFIG */ + if (input.certs_address && sev->snp_certs_data) { + if (input.certs_len < sev->snp_certs_len) { + /* Return the certs length to userspace */ + input.certs_len = sev->snp_certs_len; + + ret = -ENOSR; + goto e_done; + } +What about if input.certs_len > sev->snp_certs_len? Is it possbile for the userspace to know the length of data in the buffer? (I guess it might be able to know the certs len through the blob data, but a comment here would be nice)If userspace provides an input buffer/length smaller then snp_certs_len, then the above returns the "required" certs length back to userspace. And what is the issue if input.certs_len > sev->snp_certs_len, the buffer returned back to userspace is sev->snp_certs_len as below.My point is: How can the userspace know the length of return data is shorter than input.certs_len when input.certs_len > sev->snp_serts_len? as the length is only returned when input.certs_len < sev->snp_certs_len.
The returned data has a defined format that can be used to calculate the overall length.
Thanks, Tom
Thanks, Ashish+ if (copy_to_user((void * __user)input.certs_address, + sev->snp_certs_data, sev->snp_certs_len)) + return -EFAULT; + } + + ret = 0; + +e_done: + if (copy_to_user((void __user *)argp->data, &input, sizeof(input))) + ret = -EFAULT; + + return ret; +} + +static int sev_ioctl_snp_set_config(struct sev_issue_cmd *argp, bool writable) +{ + struct sev_device *sev = psp_master->sev_data; + struct sev_user_data_ext_snp_config input; + struct sev_user_data_snp_config config; + void *certs = NULL; + int ret = 0; + + if (!sev->snp_initialized || !argp->data) + return -EINVAL; + + if (!writable) + return -EPERM; + + memset(&input, 0, sizeof(input)); + + if (copy_from_user(&input, (void __user *)argp->data, sizeof(input))) + return -EFAULT; + + /* Copy the certs from userspace */ + if (input.certs_address) { + if (!input.certs_len || !IS_ALIGNED(input.certs_len, PAGE_SIZE)) + return -EINVAL; + + certs = psp_copy_user_blob(input.certs_address, input.certs_len); + if (IS_ERR(certs)) + return PTR_ERR(certs); + } + + /* Issue the PSP command to update the TCB version using the SNP_CONFIG. */ + if (input.config_address) { + memset(&config, 0, sizeof(config)); + if (copy_from_user(&config, + (void __user *)input.config_address, sizeof(config))) { + ret = -EFAULT; + goto e_free; + } + + ret = __sev_do_cmd_locked(SEV_CMD_SNP_CONFIG, &config, &argp->error); + if (ret) + goto e_free; + + memcpy(&sev->snp_config, &config, sizeof(config)); + } + + /* + * If the new certs are passed then cache it else free the old certs. + */ + mutex_lock(&sev->snp_certs_lock); + if (certs) { + kfree(sev->snp_certs_data); + sev->snp_certs_data = certs; + sev->snp_certs_len = input.certs_len; + } else { + kfree(sev->snp_certs_data); + sev->snp_certs_data = NULL; + sev->snp_certs_len = 0; + } + mutex_unlock(&sev->snp_certs_lock); + + return 0; + +e_free: + kfree(certs); + return ret; +} + static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) { void __user *argp = (void __user *)arg; @@ -1847,6 +1963,12 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) case SNP_PLATFORM_STATUS: ret = sev_ioctl_snp_platform_status(&input); break; + case SNP_SET_EXT_CONFIG: + ret = sev_ioctl_snp_set_config(&input, writable); + break; + case SNP_GET_EXT_CONFIG: + ret = sev_ioctl_snp_get_config(&input); + break; default: ret = -EINVAL; goto out; @@ -1962,6 +2084,7 @@ int sev_dev_init(struct psp_device *psp) goto e_sev;sev->cmd_buf_backup = (uint8_t *)sev->cmd_buf + PAGE_SIZE;+ mutex_init(&sev->snp_certs_lock);psp->sev_data = sev; diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.hindex 19d79f9d4212..41d5353d5bab 100644 --- a/drivers/crypto/ccp/sev-dev.h +++ b/drivers/crypto/ccp/sev-dev.h @@ -66,6 +66,10 @@ struct sev_device {bool snp_initialized;struct snp_host_map snp_host_map[MAX_SNP_HOST_MAP_BUFS]; + void *snp_certs_data; + u32 snp_certs_len; + struct mutex snp_certs_lock; + struct sev_user_data_snp_config snp_config; };int sev_dev_init(struct psp_device *psp);diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h index 5adfaea7df97..c20d37586d21 100644 --- a/include/uapi/linux/psp-sev.h +++ b/include/uapi/linux/psp-sev.h @@ -29,6 +29,8 @@ enum { SEV_GET_ID, /* This command is deprecated, use SEV_GET_ID2 */ SEV_GET_ID2, SNP_PLATFORM_STATUS, + SNP_SET_EXT_CONFIG, + SNP_GET_EXT_CONFIG,SEV_MAX,}; @@ -192,6 +194,21 @@ struct sev_user_data_snp_config { __u8 rsvd1[52]; } __packed;+/**+ * struct sev_data_snp_ext_config - system wide configuration value for SNP. + * + * @config_address: address of the struct sev_user_data_snp_config or 0 when + * reported_tcb does not need to be updated. + * @certs_address: address of extended guest request certificate chain or + * 0 when previous certificate should be removed on SNP_SET_EXT_CONFIG. + * @certs_len: length of the certs + */ +struct sev_user_data_ext_snp_config { + __u64 config_address; /* In */ + __u64 certs_address; /* In */ + __u32 certs_len; /* In */ +}; + /** * struct sev_issue_cmd - SEV ioctl parameters *
