[PATCH] vhost: mask VIRTIO_F_RING_RESET for vhost and vhost-user devices

[Stefano Garzarella]

Commit 69e1c14aa2 ("virtio: core: vq reset feature negotation support")
enabled VIRTIO_F_RING_RESET by default for all virtio devices.

This feature is not currently emulated by QEMU, so for vhost and
vhost-user devices we need to make sure it is supported by the offloaded
device emulation (in-kernel or in another process).
To do this we need to add VIRTIO_F_RING_RESET to the features bitmap
passed to vhost_get_features(). This way it will be masked if the device
does not support it.

This issue was initially discovered with vhost-vsock and vhost-user-vsock,
and then also tested with vhost-user-rng which confirmed the same issue.
They fail when sending features through VHOST_SET_FEATURES ioctl or
VHOST_USER_SET_FEATURES message, since VIRTIO_F_RING_RESET is negotiated
by the guest (Linux >= v6.0), but not supported by the device.

Fixes: 69e1c14aa2 ("virtio: core: vq reset feature negotation support")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1318
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---

To prevent this problem in the future, perhaps we should provide a function
(e.g. vhost_device_get_features) where we go to mask all non-device-specific
features (e.g VIRTIO_F_*, VIRTIO_RING_F_*) that are not emulated by QEMU but
we expect them to be emulated by the vhost or vhost-user devices.
Then we can call it in all .get_features callbacks just before return the
features.

What do you think?

But maybe better to do that for the next release, I will send an RFC.

Thanks,
Stefano
---
 hw/block/vhost-user-blk.c      |  1 +
 hw/net/vhost_net.c             |  1 +
 hw/scsi/vhost-scsi.c           |  1 +
 hw/scsi/vhost-user-scsi.c      |  1 +
 hw/virtio/vhost-user-fs.c      |  1 +
 hw/virtio/vhost-user-gpio.c    |  1 +
 hw/virtio/vhost-user-i2c.c     |  1 +
 hw/virtio/vhost-user-rng.c     | 11 +++++++++--
 hw/virtio/vhost-vsock-common.c |  1 +
 net/vhost-vdpa.c               |  1 +
 10 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 16ad400889..0d5190accf 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -52,6 +52,7 @@ static const int user_feature_bits[] = {
     VIRTIO_F_NOTIFY_ON_EMPTY,
     VIRTIO_F_RING_PACKED,
     VIRTIO_F_IOMMU_PLATFORM,
+    VIRTIO_F_RING_RESET,
     VHOST_INVALID_FEATURE_BIT
 };
 
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index feda448878..26e4930676 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -75,6 +75,7 @@ static const int user_feature_bits[] = {
     VIRTIO_NET_F_MTU,
     VIRTIO_F_IOMMU_PLATFORM,
     VIRTIO_F_RING_PACKED,
+    VIRTIO_F_RING_RESET,
     VIRTIO_NET_F_RSS,
     VIRTIO_NET_F_HASH_REPORT,
 
diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
index bdf337a7a2..6a0fd0dfb1 100644
--- a/hw/scsi/vhost-scsi.c
+++ b/hw/scsi/vhost-scsi.c
@@ -38,6 +38,7 @@ static const int kernel_feature_bits[] = {
     VIRTIO_RING_F_INDIRECT_DESC,
     VIRTIO_RING_F_EVENT_IDX,
     VIRTIO_SCSI_F_HOTPLUG,
+    VIRTIO_F_RING_RESET,
     VHOST_INVALID_FEATURE_BIT
 };
 
diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index bc37317d55..b7a71a802c 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -36,6 +36,7 @@ static const int user_feature_bits[] = {
     VIRTIO_RING_F_INDIRECT_DESC,
     VIRTIO_RING_F_EVENT_IDX,
     VIRTIO_SCSI_F_HOTPLUG,
+    VIRTIO_F_RING_RESET,
     VHOST_INVALID_FEATURE_BIT
 };
 
diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
index 1c40f42045..dc4014cdef 100644
--- a/hw/virtio/vhost-user-fs.c
+++ b/hw/virtio/vhost-user-fs.c
@@ -32,6 +32,7 @@ static const int user_feature_bits[] = {
     VIRTIO_F_NOTIFY_ON_EMPTY,
     VIRTIO_F_RING_PACKED,
     VIRTIO_F_IOMMU_PLATFORM,
+    VIRTIO_F_RING_RESET,
 
     VHOST_INVALID_FEATURE_BIT
 };
diff --git a/hw/virtio/vhost-user-gpio.c b/hw/virtio/vhost-user-gpio.c
index 677d1c7730..5851cb3bc9 100644
--- a/hw/virtio/vhost-user-gpio.c
+++ b/hw/virtio/vhost-user-gpio.c
@@ -24,6 +24,7 @@ static const int feature_bits[] = {
     VIRTIO_RING_F_INDIRECT_DESC,
     VIRTIO_RING_F_EVENT_IDX,
     VIRTIO_GPIO_F_IRQ,
+    VIRTIO_F_RING_RESET,
     VHOST_INVALID_FEATURE_BIT
 };
 
diff --git a/hw/virtio/vhost-user-i2c.c b/hw/virtio/vhost-user-i2c.c
index 864eba695e..1c9f3d20dc 100644
--- a/hw/virtio/vhost-user-i2c.c
+++ b/hw/virtio/vhost-user-i2c.c
@@ -16,6 +16,7 @@
 
 static const int feature_bits[] = {
     VIRTIO_I2C_F_ZERO_LENGTH_REQUEST,
+    VIRTIO_F_RING_RESET,
     VHOST_INVALID_FEATURE_BIT
 };
 
diff --git a/hw/virtio/vhost-user-rng.c b/hw/virtio/vhost-user-rng.c
index 8b47287875..f9084cde58 100644
--- a/hw/virtio/vhost-user-rng.c
+++ b/hw/virtio/vhost-user-rng.c
@@ -16,6 +16,11 @@
 #include "qemu/error-report.h"
 #include "standard-headers/linux/virtio_ids.h"
 
+static const int feature_bits[] = {
+    VIRTIO_F_RING_RESET,
+    VHOST_INVALID_FEATURE_BIT
+};
+
 static void vu_rng_start(VirtIODevice *vdev)
 {
     VHostUserRNG *rng = VHOST_USER_RNG(vdev);
@@ -106,8 +111,10 @@ static void vu_rng_set_status(VirtIODevice *vdev, uint8_t 
status)
 static uint64_t vu_rng_get_features(VirtIODevice *vdev,
                                     uint64_t requested_features, Error **errp)
 {
-    /* No feature bits used yet */
-    return requested_features;
+    VHostUserRNG *rng = VHOST_USER_RNG(vdev);
+
+    return vhost_get_features(&rng->vhost_dev, feature_bits,
+                              requested_features);
 }
 
 static void vu_rng_handle_output(VirtIODevice *vdev, VirtQueue *vq)
diff --git a/hw/virtio/vhost-vsock-common.c b/hw/virtio/vhost-vsock-common.c
index 29b9ab4f72..a67a275de2 100644
--- a/hw/virtio/vhost-vsock-common.c
+++ b/hw/virtio/vhost-vsock-common.c
@@ -21,6 +21,7 @@
 
 const int feature_bits[] = {
     VIRTIO_VSOCK_F_SEQPACKET,
+    VIRTIO_F_RING_RESET,
     VHOST_INVALID_FEATURE_BIT
 };
 
diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
index 6811089231..2b4b85d8f8 100644
--- a/net/vhost-vdpa.c
+++ b/net/vhost-vdpa.c
@@ -69,6 +69,7 @@ const int vdpa_feature_bits[] = {
     VIRTIO_NET_F_CTRL_VQ,
     VIRTIO_F_IOMMU_PLATFORM,
     VIRTIO_F_RING_PACKED,
+    VIRTIO_F_RING_RESET,
     VIRTIO_NET_F_RSS,
     VIRTIO_NET_F_HASH_REPORT,
     VIRTIO_NET_F_GUEST_ANNOUNCE,
-- 
2.38.1