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    Subject[PATCH RFC v7 59/64] ccp: Add support to decrypt the page
    Date
    From: Brijesh Singh <brijesh.singh@amd.com>

    Add support to decrypt guest encrypted memory. These API interfaces can
    be used for example to dump VMCBs on SNP guest exit.

    Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
    [mdr: minor commit fixups]
    Signed-off-by: Michael Roth <michael.roth@amd.com>
    ---
    drivers/crypto/ccp/sev-dev.c | 33 +++++++++++++++++++++++++++++++++
    include/linux/psp-sev.h | 21 ++++++++++++++++++++-
    2 files changed, 53 insertions(+), 1 deletion(-)

    diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
    index d4f13e5a8dde..052190bdb8a6 100644
    --- a/drivers/crypto/ccp/sev-dev.c
    +++ b/drivers/crypto/ccp/sev-dev.c
    @@ -2017,6 +2017,39 @@ int sev_guest_df_flush(int *error)
    }
    EXPORT_SYMBOL_GPL(sev_guest_df_flush);

    +int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *error)
    +{
    + struct sev_data_snp_dbg data = {0};
    + struct sev_device *sev;
    + int ret;
    +
    + if (!psp_master || !psp_master->sev_data)
    + return -ENODEV;
    +
    + sev = psp_master->sev_data;
    +
    + if (!sev->snp_initialized)
    + return -EINVAL;
    +
    + data.gctx_paddr = sme_me_mask | (gctx_pfn << PAGE_SHIFT);
    + data.src_addr = sme_me_mask | (src_pfn << PAGE_SHIFT);
    + data.dst_addr = sme_me_mask | (dst_pfn << PAGE_SHIFT);
    + data.len = PAGE_SIZE;
    +
    + /* The destination page must be in the firmware state. */
    + if (rmp_mark_pages_firmware(data.dst_addr, 1, false))
    + return -EIO;
    +
    + ret = sev_do_cmd(SEV_CMD_SNP_DBG_DECRYPT, &data, error);
    +
    + /* Restore the page state */
    + if (snp_reclaim_pages(data.dst_addr, 1, false))
    + ret = -EIO;
    +
    + return ret;
    +}
    +EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt_page);
    +
    int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
    unsigned long vaddr, unsigned long *npages, unsigned long *fw_err)
    {
    diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
    index 81bafc049eca..a1e6624540f3 100644
    --- a/include/linux/psp-sev.h
    +++ b/include/linux/psp-sev.h
    @@ -913,13 +913,27 @@ int sev_guest_decommission(struct sev_data_decommission *data, int *error);
    * @error: SEV command return code
    *
    * Returns:
    + * 0 if the sev successfully processed the command
    + * -%ENODEV if the sev device is not available
    + * -%ENOTSUPP if the sev does not support SEV
    + * -%ETIMEDOUT if the sev command timed out
    + * -%EIO if the sev returned a non-zero return code
    + */
    +int sev_do_cmd(int cmd, void *data, int *psp_ret);
    +
    +/**
    + * snp_guest_dbg_decrypt_page - perform SEV SNP_DBG_DECRYPT command
    + *
    + * @sev_ret: sev command return code
    + *
    + * Returns:
    * 0 if the SEV successfully processed the command
    * -%ENODEV if the SEV device is not available
    * -%ENOTSUPP if the SEV does not support SEV
    * -%ETIMEDOUT if the SEV command timed out
    * -%EIO if the SEV returned a non-zero return code
    */
    -int sev_do_cmd(int cmd, void *data, int *psp_ret);
    +int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *error);

    void *psp_copy_user_blob(u64 uaddr, u32 len);
    void *snp_alloc_firmware_page(gfp_t mask);
    @@ -987,6 +1001,11 @@ static inline void *psp_copy_user_blob(u64 __user uaddr, u32 len) { return ERR_P

    void snp_mark_pages_offline(unsigned long pfn, unsigned int npages) {}

    +static inline int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *error)
    +{
    + return -ENODEV;
    +}
    +
    static inline void *snp_alloc_firmware_page(gfp_t mask)
    {
    return NULL;
    --
    2.25.1
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