From cbad8e4cccf61c91932e7f091f9144448871c968 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Sat, 12 Mar 2016 14:41:26 +0100
Subject: [PATCH] OvmfPkg: VirtioBlkDxe: 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>
---
 OvmfPkg/VirtioBlkDxe/VirtioBlk.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/OvmfPkg/VirtioBlkDxe/VirtioBlk.c b/OvmfPkg/VirtioBlkDxe/VirtioBlk.c
index 8257effac2..f1c3f87e20 100644
--- a/OvmfPkg/VirtioBlkDxe/VirtioBlk.c
+++ b/OvmfPkg/VirtioBlkDxe/VirtioBlk.c
@@ -692,6 +692,20 @@ VirtioBlkInit (
     }
   }
 
+  Features &= VIRTIO_BLK_F_BLK_SIZE | VIRTIO_BLK_F_TOPOLOGY | VIRTIO_BLK_F_RO |
+              VIRTIO_BLK_F_FLUSH | VIRTIO_F_VERSION_1;
+
+  //
+  // In virtio-1.0, feature negotiation is expected to complete before queue
+  // discovery, and the device can also reject the selected set of features.
+  //
+  if (Dev->VirtIo->Revision >= VIRTIO_SPEC_REVISION (1, 0, 0)) {
+    Status = Virtio10WriteFeatures (Dev->VirtIo, Features, &NextDevStat);
+    if (EFI_ERROR (Status)) {
+      goto Failed;
+    }
+  }
+
   //
   // step 4b -- allocate virtqueue
   //
@@ -739,11 +753,12 @@ VirtioBlkInit (
   //
   // step 5 -- Report understood features.
   //
-  Features &= VIRTIO_BLK_F_BLK_SIZE | VIRTIO_BLK_F_TOPOLOGY | VIRTIO_BLK_F_RO |
-              VIRTIO_BLK_F_FLUSH;
-  Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo, Features);
-  if (EFI_ERROR (Status)) {
-    goto ReleaseQueue;
+  if (Dev->VirtIo->Revision < VIRTIO_SPEC_REVISION (1, 0, 0)) {
+    Features &= ~(UINT64)VIRTIO_F_VERSION_1;
+    Status = Dev->VirtIo->SetGuestFeatures (Dev->VirtIo, Features);
+    if (EFI_ERROR (Status)) {
+      goto ReleaseQueue;
+    }
   }
 
   //