On 1/12/26 17:48, Stefano Garzarella wrote:
>>>>>> diff --git a/tools/testing/vsock/vsock_test.c
>>>>>> b/tools/testing/vsock/vsock_test.c
>>>>>> index bbe3723babdc..21c8616100f1 100644
>>>>>> --- a/tools/testing/vsock/vsock_test.c
>>>>>> +++ b/tools/testing/vsock/vsock_test.c
>>>>>> @@ -2403,6 +2403,11 @@ static struct test_case test_cases[] = {
>>>>>> .run_client = test_stream_accepted_setsockopt_client,
>>>>>> .run_server = test_stream_accepted_setsockopt_server,
>>>>>> },
>>>>>> + {
>>>>>> + .name = "SOCK_STREAM MSG_ZEROCOPY coalescence
>>>>>> corruption",
>>>>>
>>>>> This is essentially a regression test for virtio transport, so I'd add
>>>>> virtio in the test name.
>>>>
>>>> Isn't virtio transport unaffected? It's about loopback transport (that
>>>> shares common code with virtio transport).
>>>
>>> Why virtio transport is not affected?
>>
>> With the usual caveat that I may be completely missing something, aren't
>> all virtio-transport's rx skbs linear? See virtio_vsock_alloc_linear_skb()
>> in virtio_vsock_rx_fill().
>>
>
> True, but what about drivers/vhost/vsock.c ?
>
> IIUC in vhost_vsock_handle_tx_kick() we call vhost_vsock_alloc_skb(),
> that calls virtio_vsock_alloc_skb() and pass that skb to
> virtio_transport_recv_pkt(). So, it's also affected right?
virtio_vsock_alloc_skb() returns a non-linear skb only if size >
SKB_WITH_OVERHEAD(PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)). And that is way
more than GOOD_COPY_LEN, so we're good.
At least until someone increases GOOD_COPY_LEN and/or reduces the size
condition for non-linear allocation. So, yeah, a bit brittle.
> BTW in general we consider loopback as one of virtio devices since it
> really shares with them most of the code.
Fair enough, I'll add "virtio" to the test name.
> That said, now I'm thinking more about Fixes tag.
> Before commit 6693731487a8 ("vsock/virtio: Allocate nonlinear SKBs for
> handling large transmit buffers") was that a real issue?
I don't really think that commit changes anything for the zerocopy case. It
only makes some big (>GOOD_COPY_LEN) non-ZC skbs turn non-linear.
