Re: [PATCH Part2 v5 16/45] crypto: ccp: Add the SNP_PLATFORM_STATUS command

On 9/22/21 12:35 PM, Dr. David Alan Gilbert wrote:

* Brijesh Singh (brijesh.singh@amd.com) wrote:

quoted

The command can be used by the userspace to query the SNP platform status
report. See the SEV-SNP spec for more details.

Signed-off-by: Brijesh Singh <redacted>
---
 Documentation/virt/coco/sevguest.rst | 27 +++++++++++++++++
 drivers/crypto/ccp/sev-dev.c         | 45 ++++++++++++++++++++++++++++
 include/uapi/linux/psp-sev.h         |  1 +
 3 files changed, 73 insertions(+)

diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst
index 7acb8696fca4..7c51da010039 100644
--- a/Documentation/virt/coco/sevguest.rst
+++ b/Documentation/virt/coco/sevguest.rst

@@ -52,6 +52,22 @@ to execute due to the firmware error, then fw_err code will be set.
                 __u64 fw_err;
         };
 
+The host ioctl should be called to /dev/sev device. The ioctl accepts command
+id and command input structure.
+
+::
+        struct sev_issue_cmd {
+                /* Command ID */
+                __u32 cmd;
+
+                /* Command request structure */
+                __u64 data;
+
+                /* firmware error code on failure (see psp-sev.h) */
+                __u32 error;
+        };
+
+
 2.1 SNP_GET_REPORT
 ------------------
 

@@ -107,3 +123,14 @@ length of the blob is lesser than expected then snp_ext_report_req.certs_len wil
 be updated with the expected value.
 
 See GHCB specification for further detail on how to parse the certificate blob.
+
+2.3 SNP_PLATFORM_STATUS
+-----------------------
+:Technology: sev-snp
+:Type: hypervisor ioctl cmd
+:Parameters (in): struct sev_data_snp_platform_status
+:Returns (out): 0 on success, -negative on error
+
+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.

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 4cd7d803a624..16c6df5d412c 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c

@@ -1394,6 +1394,48 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp, bool writable)
 	return ret;
 }
 
+static int sev_ioctl_snp_platform_status(struct sev_issue_cmd *argp)
+{
+	struct sev_device *sev = psp_master->sev_data;
+	struct sev_data_snp_platform_status_buf buf;
+	struct page *status_page;
+	void *data;
+	int ret;
+
+	if (!sev->snp_inited || !argp->data)
+		return -EINVAL;
+
+	status_page = alloc_page(GFP_KERNEL_ACCOUNT);
+	if (!status_page)
+		return -ENOMEM;
+
+	data = page_address(status_page);
+	if (snp_set_rmp_state(__pa(data), 1, true, true, false)) {
+		__free_pages(status_page, 0);
+		return -EFAULT;
+	}
+
+	buf.status_paddr = __psp_pa(data);
+	ret = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &argp->error);
+
+	/* Change the page state before accessing it */
+	if (snp_set_rmp_state(__pa(data), 1, false, true, true)) {
+		snp_leak_pages(__pa(data) >> PAGE_SHIFT, 1);
+		return -EFAULT;
+	}

Could we find a way of returning some of these errors into the output,
rather than interepreting them from errno values?

I can try to find a corresponding fw error code and use it where
applicable. e.g in this case I can use the SEV_RET_INVALID_PAGE_STATE.

thanks