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    SubjectRe: [PATCH Part2 v5 18/45] crypto: ccp: Provide APIs to query extended attestation report
    On Fri, Aug 20, 2021 at 9:00 AM Brijesh Singh <brijesh.singh@amd.com> wrote:
    >
    > Version 2 of the GHCB specification defines VMGEXIT that is used to get
    > the extended attestation report. The extended attestation report includes
    > the certificate blobs provided through the SNP_SET_EXT_CONFIG.
    >
    > The snp_guest_ext_guest_request() will be used by the hypervisor to get
    > the extended attestation report. See the GHCB specification for more
    > details.
    >
    > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    > ---
    > drivers/crypto/ccp/sev-dev.c | 43 ++++++++++++++++++++++++++++++++++++
    > include/linux/psp-sev.h | 24 ++++++++++++++++++++
    > 2 files changed, 67 insertions(+)
    >
    > diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
    > index 9ba194acbe85..e2650c3d0d0a 100644
    > --- a/drivers/crypto/ccp/sev-dev.c
    > +++ b/drivers/crypto/ccp/sev-dev.c
    > @@ -22,6 +22,7 @@
    > #include <linux/firmware.h>
    > #include <linux/gfp.h>
    > #include <linux/cpufeature.h>
    > +#include <linux/sev-guest.h>
    >
    > #include <asm/smp.h>
    >
    > @@ -1677,6 +1678,48 @@ int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error)
    > }
    > EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt);
    >
    > +int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
    > + unsigned long vaddr, unsigned long *npages, unsigned long *fw_err)
    > +{
    > + unsigned long expected_npages;
    > + struct sev_device *sev;
    > + int rc;
    > +
    > + if (!psp_master || !psp_master->sev_data)
    > + return -ENODEV;
    > +
    > + sev = psp_master->sev_data;
    > +
    > + if (!sev->snp_inited)
    > + return -EINVAL;
    > +
    > + /*
    > + * Check if there is enough space to copy the certificate chain. Otherwise
    > + * return ERROR code defined in the GHCB specification.
    > + */
    > + expected_npages = sev->snp_certs_len >> PAGE_SHIFT;

    Is this calculation for `expected_npages` correct? Assume that
    `sev->snp_certs_len` is less than a page (e.g., 2000). Then, this
    calculation will return `0` for `expected_npages`, rather than round
    up to 1.

    > + if (*npages < expected_npages) {
    > + *npages = expected_npages;
    > + *fw_err = SNP_GUEST_REQ_INVALID_LEN;
    > + return -EINVAL;
    > + }
    > +
    > + rc = sev_do_cmd(SEV_CMD_SNP_GUEST_REQUEST, data, (int *)&fw_err);
    > + if (rc)
    > + return rc;
    > +
    > + /* Copy the certificate blob */
    > + if (sev->snp_certs_data) {
    > + *npages = expected_npages;
    > + memcpy((void *)vaddr, sev->snp_certs_data, *npages << PAGE_SHIFT);
    > + } else {
    > + *npages = 0;
    > + }
    > +
    > + return rc;
    > +}
    > +EXPORT_SYMBOL_GPL(snp_guest_ext_guest_request);
    > +
    > static void sev_exit(struct kref *ref)
    > {
    > misc_deregister(&misc_dev->misc);
    > diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
    > index 00bd684dc094..ea94ce4d834a 100644
    > --- a/include/linux/psp-sev.h
    > +++ b/include/linux/psp-sev.h
    > @@ -924,6 +924,23 @@ void *psp_copy_user_blob(u64 uaddr, u32 len);
    > void *snp_alloc_firmware_page(gfp_t mask);
    > void snp_free_firmware_page(void *addr);
    >
    > +/**
    > + * snp_guest_ext_guest_request - perform the SNP extended guest request command
    > + * defined in the GHCB specification.
    > + *
    > + * @data: the input guest request structure
    > + * @vaddr: address where the certificate blob need to be copied.
    > + * @npages: number of pages for the certificate blob.
    > + * If the specified page count is less than the certificate blob size, then the
    > + * required page count is returned with error code defined in the GHCB spec.
    > + * If the specified page count is more than the certificate blob size, then
    > + * page count is updated to reflect the amount of valid data copied in the
    > + * vaddr.
    > + */
    > +int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
    > + unsigned long vaddr, unsigned long *npages,
    > + unsigned long *error);
    > +
    > #else /* !CONFIG_CRYPTO_DEV_SP_PSP */
    >
    > static inline int
    > @@ -971,6 +988,13 @@ static inline void *snp_alloc_firmware_page(gfp_t mask)
    >
    > static inline void snp_free_firmware_page(void *addr) { }
    >
    > +static inline int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
    > + unsigned long vaddr, unsigned long *n,
    > + unsigned long *error)
    > +{
    > + return -ENODEV;
    > +}
    > +
    > #endif /* CONFIG_CRYPTO_DEV_SP_PSP */
    >
    > #endif /* __PSP_SEV_H__ */
    > --
    > 2.17.1
    >

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