qemu-kvm/kvm-vhost-vdpa-backend-feature-should-set-only-once.patch

From 01270bb66a4f7897a4fd06ba248eeeb41dc47571 Mon Sep 17 00:00:00 2001
From: Si-Wei Liu <si-wei.liu@oracle.com>
Date: Fri, 6 May 2022 19:28:16 -0700
Subject: [PATCH 18/24] vhost-vdpa: backend feature should set only once
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RH-Author: Jason Wang <jasowang@redhat.com>
RH-MergeRequest: 187: Multiqueue fixes for vhost-vDPA
RH-Commit: [5/7] 0ab13542cf25c129dc403db95c7db12cdb012744
RH-Bugzilla: 2069946
RH-Acked-by: Eugenio Pérez <eperezma@redhat.com>
RH-Acked-by: Cindy Lu <lulu@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

The vhost_vdpa_one_time_request() branch in
vhost_vdpa_set_backend_cap() incorrectly sends down
ioctls on vhost_dev with non-zero index. This may
end up with multiple VHOST_SET_BACKEND_FEATURES
ioctl calls sent down on the vhost-vdpa fd that is
shared between all these vhost_dev's.

To fix it, send down ioctl only once via the first
vhost_dev with index 0. Toggle the polarity of the
vhost_vdpa_one_time_request() test should do the
trick.

Fixes: 4d191cfdc7de ("vhost-vdpa: classify one time request")
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <1651890498-24478-6-git-send-email-si-wei.liu@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 6aee7e4233f6467f69531fcd352adff028f3f5ea)
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 78da48a333..a9be24776a 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -525,7 +525,7 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev *dev)
 
     features &= f;
 
-    if (vhost_vdpa_one_time_request(dev)) {
+    if (!vhost_vdpa_one_time_request(dev)) {
         r = vhost_vdpa_call(dev, VHOST_SET_BACKEND_FEATURES, &features);
         if (r) {
             return -EFAULT;
-- 
2.35.3