Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Feedback-ID: id4a34324:Fastmail
Date:   Mon, 15 Aug 2022 10:46:17 -0700
From:   Andres Freund <andres@anarazel.de>
To:     "Michael S. Tsirkin" <mst@redhat.com>
Cc:     Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Jens Axboe <axboe@kernel.dk>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Guenter Roeck <linux@roeck-us.net>,
        linux-kernel@vger.kernel.org, Greg KH <gregkh@linuxfoundation.org>,
        c@redhat.com
Subject: Re: upstream kernel crashes
Message-ID: <20220815174617.z4chnftzcbv6frqr@awork3.anarazel.de>
References: <20220815013651.mrm7qgklk6sgpkbb@awork3.anarazel.de>
 <CAHk-=wikzU4402P-FpJRK_QwfVOS+t-3p1Wx5awGHTvr-s_0Ew@mail.gmail.com>
 <20220815071143.n2t5xsmifnigttq2@awork3.anarazel.de>
 <20220815034532-mutt-send-email-mst@kernel.org>
 <20220815081527.soikyi365azh5qpu@awork3.anarazel.de>
 <20220815042623-mutt-send-email-mst@kernel.org>
 <FCDC5DDE-3CDD-4B8A-916F-CA7D87B547CE@anarazel.de>
 <20220815113729-mutt-send-email-mst@kernel.org>
 <20220815164503.jsoezxcm6q4u2b6j@awork3.anarazel.de>
 <20220815124748-mutt-send-email-mst@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220815124748-mutt-send-email-mst@kernel.org>
Precedence: bulk

Hi,

On 2022-08-15 12:50:52 -0400, Michael S. Tsirkin wrote:
> On Mon, Aug 15, 2022 at 09:45:03AM -0700, Andres Freund wrote:
> > Hi,
> > 
> > On 2022-08-15 11:40:59 -0400, Michael S. Tsirkin wrote:
> > > OK so this gives us a quick revert as a solution for now.
> > > Next, I would appreciate it if you just try this simple hack.
> > > If it crashes we either have a long standing problem in virtio
> > > code or more likely a gcp bug where it can't handle smaller
> > > rings than what device requestes.
> > > Thanks!
> > 
> > I applied the below and the problem persists.
> > 
> > [...]
>
> Okay!

Just checking - I applied and tested this atop 6.0-rc1, correct? Or did you
want me to test it with the 762faee5a267 reverted? I guess what you're trying
to test if a smaller queue than what's requested you'd want to do so without
the problematic patch applied...


> And just to be 100% sure, can you try the following on top of 5.19:

> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 623906b4996c..6f4e54a618bc 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -208,6 +208,9 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> +	if (num > 1024)
> +		num = 1024;
> +
>  	info->msix_vector = msix_vec;
>  
>  	/* create the vring */
> 
> -- 

Either way, I did this, and there are no issues that I could observe. No
oopses, no broken networking. But:

To make sure it does something I added a debugging printk - which doesn't show
up. I assume this is at a point at least earlyprintk should work (which I see
getting enabled via serial)?

Greetings,

Andres Freund