Hi Brijesh,

On 08/10/2021 21:04, Brijesh Singh wrote:

SEV-SNP specification provides the guest a mechanisum to communicate with
the PSP without risk from a malicious hypervisor who wishes to read, alter,
drop or replay the messages sent. The driver uses snp_issue_guest_request()
to issue GHCB SNP_GUEST_REQUEST or SNP_EXT_GUEST_REQUEST NAE events to
submit the request to PSP.

The PSP requires that all communication should be encrypted using key
specified through the platform_data.

The userspace can use SNP_GET_REPORT ioctl() to query the guest
attestation report.

See SEV-SNP spec section Guest Messages for more details.

Signed-off-by: Brijesh Singh <redacted>
---
 Documentation/virt/coco/sevguest.rst  |  77 ++++
 drivers/virt/Kconfig                  |   3 +
 drivers/virt/Makefile                 |   1 +
 drivers/virt/coco/sevguest/Kconfig    |   9 +
 drivers/virt/coco/sevguest/Makefile   |   2 +
 drivers/virt/coco/sevguest/sevguest.c | 561 ++++++++++++++++++++++++++
 drivers/virt/coco/sevguest/sevguest.h |  98 +++++
 include/uapi/linux/sev-guest.h        |  44 ++
 8 files changed, 795 insertions(+)
 create mode 100644 Documentation/virt/coco/sevguest.rst
 create mode 100644 drivers/virt/coco/sevguest/Kconfig
 create mode 100644 drivers/virt/coco/sevguest/Makefile
 create mode 100644 drivers/virt/coco/sevguest/sevguest.c
 create mode 100644 drivers/virt/coco/sevguest/sevguest.h
 create mode 100644 include/uapi/linux/sev-guest.h

[...]

+
+static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
+{
+	u8 *key = NULL;
+
+	switch (id) {
+	case 0:
+		*seqno = &layout->os_area.msg_seqno_0;
+		key = layout->vmpck0;
+		break;
+	case 1:
+		*seqno = &layout->os_area.msg_seqno_1;
+		key = layout->vmpck1;
+		break;
+	case 2:
+		*seqno = &layout->os_area.msg_seqno_2;
+		key = layout->vmpck2;
+		break;
+	case 3:
+		*seqno = &layout->os_area.msg_seqno_3;
+		key = layout->vmpck3;
+		break;
+	default:
+		break;
+	}
+
+	return NULL;

This should be 'return key', right?

-Dov

+}
+