linux-kernel - Re: [PATCH] virtio: use virtio_device_ready() in virtio_device

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Date:   Tue, 22 Mar 2022 10:07:08 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH] virtio: use virtio_device_ready() in
 virtio_device_restore()

On Tue, Mar 22, 2022 at 12:43:13PM +0100, Stefano Garzarella wrote:
> After waking up a suspended VM, the kernel prints the following trace
> for virtio drivers which do not directly call virtio_device_ready() in
> the .restore:
> 
>     PM: suspend exit
>     irq 22: nobody cared (try booting with the "irqpoll" option)
>     Call Trace:
>      <IRQ>
>      dump_stack_lvl+0x38/0x49
>      dump_stack+0x10/0x12
>      __report_bad_irq+0x3a/0xaf
>      note_interrupt.cold+0xb/0x60
>      handle_irq_event+0x71/0x80
>      handle_fasteoi_irq+0x95/0x1e0
>      __common_interrupt+0x6b/0x110
>      common_interrupt+0x63/0xe0
>      asm_common_interrupt+0x1e/0x40
>      ? __do_softirq+0x75/0x2f3
>      irq_exit_rcu+0x93/0xe0
>      sysvec_apic_timer_interrupt+0xac/0xd0
>      </IRQ>
>      <TASK>
>      asm_sysvec_apic_timer_interrupt+0x12/0x20
>      arch_cpu_idle+0x12/0x20
>      default_idle_call+0x39/0xf0
>      do_idle+0x1b5/0x210
>      cpu_startup_entry+0x20/0x30
>      start_secondary+0xf3/0x100
>      secondary_startup_64_no_verify+0xc3/0xcb
>      </TASK>
>     handlers:
>     [<000000008f9bac49>] vp_interrupt
>     [<000000008f9bac49>] vp_interrupt
>     Disabling IRQ #22
> 
> This happens because we don't invoke .enable_cbs callback in
> virtio_device_restore(). That callback is used by some transports
> (e.g. virtio-pci) to enable interrupts.
> 
> Let's fix it, by calling virtio_device_ready() as we do in
> virtio_dev_probe(). This function calls .enable_cts callback and sets
> DRIVER_OK status bit.
> 
> This fix also avoids setting DRIVER_OK twice for those drivers that
> call virtio_device_ready() in the .restore.
> 
> Fixes: d50497eb4e55 ("virtio_config: introduce a new .enable_cbs method")
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
> 
> I'm not sure about the fixes tag. That one is more generic, but the
> following one I think introduced the issue.
> 
> Fixes: 9e35276a5344 ("virtio_pci: harden MSI-X interrupts")

Jason what should we do about this one BTW? Just revert? We have other
issues ...


> Thanks,
> Stefano
> ---
>  drivers/virtio/virtio.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 22f15f444f75..75c8d560bbd3 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -526,8 +526,9 @@ int virtio_device_restore(struct virtio_device *dev)
>  			goto err;
>  	}
>  
> -	/* Finally, tell the device we're all set */
> -	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
> +	/* If restore didn't do it, mark device DRIVER_OK ourselves. */
> +	if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
> +		virtio_device_ready(dev);
>  
>  	virtio_config_enable(dev);
>  
> -- 
> 2.35.1