linux-kernel - Re: Random guest crashes since 5c34d002dcc7 ("virtio_pci: use shared interrupts for virtqueues")

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Message-ID: <20170327211246-mutt-send-email-mst@kernel.org>
Date:   Mon, 27 Mar 2017 21:16:12 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Mike Galbraith <efault@....de>,
        Thorsten Leemhuis <linux@...mhuis.info>,
        virtio-dev@...ts.oasis-open.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        rjones@...hat.com
Subject: Re: Random guest crashes since 5c34d002dcc7 ("virtio_pci: use shared
 interrupts for virtqueues")

On Mon, Mar 27, 2017 at 07:05:40PM +0200, Christoph Hellwig wrote:
> Hi Mike,
> 
> does the patch below fix that issue for you?
> 
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index df548a6fb844..fd1b06368b1f 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -176,7 +176,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
>  	if (err < 0)
>  		return err;
>  
> -	vp_dev->msix_vectors = nvectors;
> +	vp_dev->msix_vectors = err; /* number of vectors allocated */
>  	vp_dev->msix_names = kmalloc_array(nvectors,
>  			sizeof(*vp_dev->msix_names), GFP_KERNEL);
>  	if (!vp_dev->msix_names)

Can this sometimes allocate less vectors than min number requested then?
I didn't realize.

In that case we probably should change if (err < 0)
to if (err != nvectors) and similarly for when we try
to get 2 vectors.


Mike, could you pls send lspci -vv that shows up after
boot?

-- 
MST