Re: [PATCH] block/vhost-user-blk: Fix hang on boot for some odd guests

[Andrey Ryabinin]

On 4/18/23 08:17, Michael S. Tsirkin wrote:
> On Tue, Apr 18, 2023 at 05:13:11AM +0000, Raphael Norwitz wrote:
>> Hey Andrey - apologies for the late reply here.
>>
>> It sounds like you are dealing with a buggy guest, rather than a QEMU issue.
>>
>>> On Apr 10, 2023, at 11:39 AM, Andrey Ryabinin <arbn@yandex-team.com> wrote:
>>>
>>>
>>>
>>> On 4/10/23 10:35, Andrey Ryabinin wrote:
>>>> Some guests hang on boot when using the vhost-user-blk-pci device,
>>>> but boot normally when using the virtio-blk device. The problem occurs
>>>> because the guest advertises VIRTIO_F_VERSION_1 but kicks the virtqueue
>>>> before setting VIRTIO_CONFIG_S_DRIVER_OK, causing vdev->start_on_kick to
>>
>> Virtio 1.1 Section 3.1.1, says during setup “[t]he driver MUST NOT notify 
>> the device before setting DRIVER_OK.”
>>
>> Therefore what you are describing is buggy guest behavior. Sounds like the 
>> driver should be made to either
>> - not advertise VIRTIO_F_VERSION_1
>> - not kick before setting VIRTIO_CONFIG_S_DRIVER_OK
>>
>> If anything, the virtio-blk virtio_blk_handle_output() function should 
>> probably check start_on_kick?
> 
> Question is, how easy is this guest to fix.
> 

I wouldn't count on that.

In this case the guest is Foritgate firewall, apparently from this guys 
https://www.fortinet.com/
It seems that the kernel they use claims itself as 3.2.16 Linux kernel, however 
it looks like
it's not vanilla kernel, but modified with some backports. I'm guessing that 
they backported
the patches introducing VIRTIO_F_VERSTION_1, but they didn't add this patch 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7a11370e5e6c26566904bb7f08281093a3002ff2

I've tried to look the sources of the kernel they use but failed to find any.
Found only some news about gpl voilation from 2005 )