Re: [PATCH v2] vhost: don't set vring call if guest notifiers is not enabled

2024-04-09 Thread Gavin Liu


Hi Michael,

― ✀  ―
stderr:
**
ERROR:../tests/qtest/vhost-user-test.c:468:chr_read: assertion failed (err == 
NULL): Bad file descriptor (g-unix-error-quark, 0)
**
ERROR:../tests/qtest/qos-test.c:191:subprocess_run_one_test: child process 
(/aarch64/virt/generic-pcihost/pci-bus-generic/pci-bus/virtio-net-pci/virtio-net/virtio-net-tests/vhost-user/migrate/subprocess
 [22197]) failed unexpectedly (test program exited with status code -6) ――
___


When I analyze the problem, the scenario might be like this:
一、vhost user server:
   1:set call fd -1
   2:The function vhost_user_set_vring_call invokes vhost_set_vring_file to 
send the file descriptor information, where fd=-1, thus fd_num=0
   3: The function call vhost_user_write(dev, , fds, fd_num) sends to the 
vhost user client.  
   
二、vhost user client
   1: The function call vhost_user_read receives the file descriptor 
information sent by the server.
   2: SocketChardev *s = SOCKET_CHARDEV(chr); Update s->read_msgfds_num = 
msgfds_num = 0.
   
三、tests/qtest/vhost-user-test
   1:vhost-user-test invokes the chr_read function to handle the messages sent 
by the server.
   2:The chr_read function initializes the local variable fd to -1.
   3:
case VHOST_USER_SET_VRING_CALL:
qemu_chr_fe_get_msgfds(chr, , 1); 

!!! Because s->read_msgfds_num = 0, after the function 
qemu_chr_fe_get_msgfds(chr, , 1) is executed, fd=-1.!!!

g_unix_set_fd_nonblocking(fd, true, ); 

!!! An exception will occur when setting nonblocking when fd < 0. !!!   
g_assert_no_error(err);

四、Offer a modification suggestion
   1:Refer to the tcp_chr_recv function:
static ssize_t 
tcp_chr_recv(Chardev *chr, char *buf, size_t len)
{
SocketChardev *s = 
SOCKET_CHARDEV(chr);
  -
  
for (i = 0; i < 
s->read_msgfds_num; i++) {
int fd = 
s->read_msgfds[i];
if (fd < 0) {
When fd < 0, the qemu_socket_set_block 
function will not be called  

continue;
}

/* O_NONBLOCK 
is preserved across SCM_RIGHTS so reset it */

qemu_socket_set_block(fd);

   2: modify chr_read function 

case VHOST_USER_SET_VRING_CALL:
qemu_chr_fe_get_msgfds(chr, 
, 1); 
if (fd <0)   /* Add a condition 
check. */
break;
g_unix_set_fd_nonblocking(fd, 
true, ); 
g_assert_no_error(err);

Best regards,
Yuxue Liu


__

- Original Message -
From: Michael S. Tsirkin m...@redhat.com
Sent: April 9, 2024 17:31
To: Gavin Liu gavin@jaguarmicro.com
Cc: jasow...@redhat.com; qemu-sta...@nongnu.org; qemu-devel@nongnu.org
Subject: Re: [PATCH] vhost: don't set vring call if no enabled msix



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On Mon, Apr 08, 2024 at 03:33:11PM +0800, lyx634449800 wrote:
> When conducting performance testing using testpmd in the guest os, it 
> was observed that the performance was lower compared to the scenario 
> of direct vfio-pci usage.
>
> In the commit 96a3d98d2cdbd897ff5ab33427aa4cfb94077665, the author 
> provided a good solution. However, because the guest OS's driver(e.g., 
> virtio-net pmd) may not enable the msix capability, the function 
> k->query_guest_notifiers(qbus->parent) may return false, resulting in 
> the expected effect not being achieved. To address this issue, modify 
> the conditional statement.
>
> Signed-off-by: Yuxue Liu 


I tested v1 and it fails. Sent as reply on that patch.
Since all you did is 

Re: [PATCH v2] vhost: don't set vring call if guest notifiers is not enabled

2024-04-09 Thread Michael S. Tsirkin
On Mon, Apr 08, 2024 at 03:33:11PM +0800, lyx634449800 wrote:
> When conducting performance testing using testpmd in the guest os,
> it was observed that the performance was lower compared to the
> scenario of direct vfio-pci usage.
> 
> In the commit 96a3d98d2cdbd897ff5ab33427aa4cfb94077665, the author
> provided a good solution. However, because the guest OS's
> driver(e.g., virtio-net pmd) may not enable the msix capability, the
> function k->query_guest_notifiers(qbus->parent) may return false,
> resulting in the expected effect not being achieved. To address this
> issue, modify the conditional statement.
> 
> Signed-off-by: Yuxue Liu 


I tested v1 and it fails. Sent as reply on that patch.
Since all you did is tweak description and title the
problem is probably still there in v2.

> ---
> V2: Update commit description and title
> 
>  hw/virtio/vhost.c | 16 +---
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index f50180e60e..b972c84e67 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1266,13 +1266,15 @@ int vhost_virtqueue_start(struct vhost_dev *dev,
>  vhost_virtqueue_mask(dev, vdev, idx, false);
>  }
>  
> -if (k->query_guest_notifiers &&
> -k->query_guest_notifiers(qbus->parent) &&
> -virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) {
> -file.fd = -1;
> -r = dev->vhost_ops->vhost_set_vring_call(dev, );
> -if (r) {
> -goto fail_vector;
> +if (k->query_guest_notifiers) {
> +if (!k->query_guest_notifiers(qbus->parent) ||
> +(k->query_guest_notifiers(qbus->parent) &&
> +virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR)) {
> +file.fd = -1;
> +r = dev->vhost_ops->vhost_set_vring_call(dev, );
> +if (r) {
> +goto fail_vector;
> +}
>  }
>  }
>  
> -- 
> 2.43.0




Re: [PATCH v2] vhost: don't set vring call if guest notifiers is not enabled

2024-04-08 Thread Jason Wang
On Mon, Apr 8, 2024 at 3:33 PM lyx634449800  wrote:
>
> When conducting performance testing using testpmd in the guest os,
> it was observed that the performance was lower compared to the
> scenario of direct vfio-pci usage.
>
> In the commit 96a3d98d2cdbd897ff5ab33427aa4cfb94077665, the author
> provided a good solution. However, because the guest OS's
> driver(e.g., virtio-net pmd) may not enable the msix capability, the
> function k->query_guest_notifiers(qbus->parent) may return false,
> resulting in the expected effect not being achieved. To address this
> issue, modify the conditional statement.
>
> Signed-off-by: Yuxue Liu 

Acked-by: Jason Wang 

Thanks




[PATCH v2] vhost: don't set vring call if guest notifiers is not enabled

2024-04-08 Thread lyx634449800
When conducting performance testing using testpmd in the guest os,
it was observed that the performance was lower compared to the
scenario of direct vfio-pci usage.

In the commit 96a3d98d2cdbd897ff5ab33427aa4cfb94077665, the author
provided a good solution. However, because the guest OS's
driver(e.g., virtio-net pmd) may not enable the msix capability, the
function k->query_guest_notifiers(qbus->parent) may return false,
resulting in the expected effect not being achieved. To address this
issue, modify the conditional statement.

Signed-off-by: Yuxue Liu 
---
V2: Update commit description and title

 hw/virtio/vhost.c | 16 +---
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index f50180e60e..b972c84e67 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1266,13 +1266,15 @@ int vhost_virtqueue_start(struct vhost_dev *dev,
 vhost_virtqueue_mask(dev, vdev, idx, false);
 }
 
-if (k->query_guest_notifiers &&
-k->query_guest_notifiers(qbus->parent) &&
-virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) {
-file.fd = -1;
-r = dev->vhost_ops->vhost_set_vring_call(dev, );
-if (r) {
-goto fail_vector;
+if (k->query_guest_notifiers) {
+if (!k->query_guest_notifiers(qbus->parent) ||
+(k->query_guest_notifiers(qbus->parent) &&
+virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR)) {
+file.fd = -1;
+r = dev->vhost_ops->vhost_set_vring_call(dev, );
+if (r) {
+goto fail_vector;
+}
 }
 }
 
-- 
2.43.0