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

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Message-ID: <CACGkMEscqtaTpCed_f2cfknO4--mXCyp33u1CmZwNEZxyf=ifQ@mail.gmail.com>
Date:   Tue, 11 Apr 2023 13:24:03 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Angus Chen <angus.chen@...uarmicro.com>
Cc:     mst@...hat.com, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_pci: Wait for legacy device to be reset

On Tue, Apr 11, 2023 at 9:39 AM Angus Chen <angus.chen@...uarmicro.com> wrote:
>
> 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.

The only concern is if it's too late to do this.

Btw, any reason you want to have a legacy hardware implementation. It
will be very tricky to work correctly.

Thanks

>
> 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
>