linux-kernel - RE: [PATCH] virtio_pci: Wait for legacy device to be reset

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Message-ID: <TY2PR06MB342406D4DAA8F62140E461DC859A9@TY2PR06MB3424.apcprd06.prod.outlook.com>
Date:   Tue, 11 Apr 2023 01:47:00 +0000
From:   Angus Chen <angus.chen@...uarmicro.com>
To:     "mst@...hat.com" <mst@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>
CC:     "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] virtio_pci: Wait for legacy device to be reset

Hi.

We got a legacy probe problem multitimes.
After reset the legacy device,and we probe the device quickly,
We often get the wrong status of device , especially use in vdpa with legacy moden.
It's often occurs in the set vq status ioctl.

If we use modern virtio device ,it is disappear.

Thanks.

> -----Original Message-----
> From: Angus Chen
> Sent: Tuesday, April 11, 2023 9:39 AM
> To: mst@...hat.com; jasowang@...hat.com
> Cc: virtualization@...ts.linux-foundation.org; linux-kernel@...r.kernel.org;
> Angus Chen <angus.chen@...uarmicro.com>
> Subject: [PATCH] virtio_pci: Wait for legacy device to be reset
> 
> We read the status of device after reset,
> It is not guaranteed that the device be reseted successfully.
> We can use a while loop to make sure that,like the modern device did.
> The spec is not request it ,but it work.
> 
> Signed-off-by: Angus Chen <angus.chen@...uarmicro.com>
> ---
>  drivers/virtio/virtio_pci_legacy.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> index 2257f1b3d8ae..f2d241563e4f 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -14,6 +14,7 @@
>   *  Michael S. Tsirkin <mst@...hat.com>
>   */
> 
> +#include <linux/delay.h>
>  #include "linux/virtio_pci_legacy.h"
>  #include "virtio_pci_common.h"
> 
> @@ -97,7 +98,8 @@ static void vp_reset(struct virtio_device *vdev)
>  	vp_legacy_set_status(&vp_dev->ldev, 0);
>  	/* Flush out the status write, and flush in device writes,
>  	 * including MSi-X interrupts, if any. */
> -	vp_legacy_get_status(&vp_dev->ldev);
> +	while (vp_legacy_get_status(&vp_dev->ldev))
> +		msleep(1);
>  	/* Flush pending VQ/configuration callbacks. */
>  	vp_synchronize_vectors(vdev);
>  }
> --
> 2.25.1