OvmfPkg: VirtioScsiDxe: adapt feature negotiation to virtio-1.0

Relative to virtio-0.9.5, virtio-1.0 reverses the order of queue discovery
and feature negotiation. In virtio-1.0, feature negotiation has to
complete first, and the device can also reject a self-inconsistent feature
request through the new VSTAT_FEATURES_OK status bit. (For example if the
driver requests a higher level feature but clears a prerequisite feature.)

Furthermore, we retain the VIRTIO_F_VERSION_1 feature bit if the
VIRTIO_DEVICE_PROTOCOL provider has high enough revision.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

diff --git a/OvmfPkg/VirtioScsiDxe/VirtioScsi.c b/OvmfPkg/VirtioScsiDxe/VirtioScsi.c
index 162577bcb9611c7b8610d0c5de8ec6de72ef8524..c080404330e55a941507a488b61e08626bab7601 100644 (file)
--- a/OvmfPkg/VirtioScsiDxe/VirtioScsi.c
+++ b/OvmfPkg/VirtioScsiDxe/VirtioScsi.c
@@ -800,6 +800,19 @@ VirtioScsiInit (
     goto Failed;\r
   }\r
 \r
+  Features &= VIRTIO_SCSI_F_INOUT | VIRTIO_F_VERSION_1;\r
+\r
+  //\r
+  // In virtio-1.0, feature negotiation is expected to complete before queue\r
+  // discovery, and the device can also reject the selected set of features.\r
+  //\r
+  if (Dev->VirtIo->Revision >= VIRTIO_SPEC_REVISION (1, 0, 0)) {\r
+    Status = Virtio10WriteFeatures (Dev->VirtIo, Features, &NextDevStat);\r
+    if (EFI_ERROR (Status)) {\r
+      goto Failed;\r
+    }\r
+  }\r
+\r
   //\r
   // step 4b -- allocate request virtqueue\r
   //\r
@@ -847,14 +860,14 @@ VirtioScsiInit (
   }\r
 \r
   //\r
-  // step 5 -- Report understood features and guest-tuneables. We want none of\r
-  // the known (or unknown) VIRTIO_SCSI_F_* or VIRTIO_F_* capabilities (see\r
-  // virtio-0.9.5, Appendices B and I), except bidirectional transfers.\r
+  // step 5 -- Report understood features and guest-tuneables.\r
   //\r
-  Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo,\r
-      Features & VIRTIO_SCSI_F_INOUT);\r
-  if (EFI_ERROR (Status)) {\r
-    goto ReleaseQueue;\r
+  if (Dev->VirtIo->Revision < VIRTIO_SPEC_REVISION (1, 0, 0)) {\r
+    Features &= ~(UINT64)VIRTIO_F_VERSION_1;\r
+    Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo, Features);\r
+    if (EFI_ERROR (Status)) {\r
+      goto ReleaseQueue;\r
+    }\r
   }\r
 \r
   //\r