Messages in this thread | | | Date | Thu, 23 Feb 2023 08:19:31 -0600 | Subject | Re: [PATCH RFC v8 27/56] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command | From | Tom Lendacky <> |
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On 2/23/23 00:38, Zhi Wang wrote: > On Wed, 22 Feb 2023 16:43:54 -0600 > "Kalra, Ashish" <ashish.kalra@amd.com> wrote: > >> On 2/22/2023 6:32 AM, Zhi Wang wrote: >>> On Mon, 20 Feb 2023 12:38:18 -0600 >>> Michael Roth <michael.roth@amd.com> wrote: >>> >>>> From: Brijesh Singh <brijesh.singh@amd.com> >>>> >>>> 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@amd.com> >>>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> >>>> Signed-off-by: Michael Roth <michael.roth@amd.com> >>>> --- >>>> 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.
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.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 >>>> * >>> >
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