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.c > >> index 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. > 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.h > >> index 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 > >> * > >