linux-kernel - Re: [PATCH] tools/virtio: Test virtual address range detection

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Date:   Mon, 21 Feb 2022 17:18:48 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tools/virtio: Test virtual address range detection

On Mon, 2022-02-21 at 18:02 +0100, Stefano Garzarella wrote:
> On Mon, Feb 21, 2022 at 04:15:22PM +0000, David Woodhouse wrote:
> > As things stand, an application which wants to use vhost with a trivial
> > 1:1 mapping of its virtual address space is forced to jump through hoops
> > to detect what the address range might be. The VHOST_SET_MEM_TABLE ioctl
> > helpfully doesn't fail immediately; you only get a failure *later* when
> > you attempt to set the backend, if the table *could* map to an address
> > which is out of range, even if no out-of-range address is actually
> > being referenced.
> > 
> > Since userspace is growing workarounds for this lovely kernel API, let's
> > ensure that we have a regression test that does things basically the same
> > way as 
> > https://gitlab.com/openconnect/openconnect/-/commit/443edd9d8826
> > 
> > does.
> > 
> > This is untested as I can't actually get virtio_test to work at all; it
> > just seems to deadlock on a spinlock. But it's getting the right answer
> > for the virtio range on x86_64 at least.
> 
> I had a similar issue with virtio_test and this simple patch [1] should 
> fix the deadlock.
> 
> [1] 
> https://lore.kernel.org/lkml/20220118150631.167015-1-sgarzare@redhat.com/=

Thanks.

[dwoodhou@i7 virtio]$ sudo ~/virtio_test
Detected virtual address range 0x1000-0x7ffffffff000
spurious wakeups: 0x0 started=0x100000 completed=0x100000

Although in some circumstances I also see a different build failure:

cc -g -O2 -Werror -Wno-maybe-uninitialized -Wall -I. -I../include/ -I ../../usr/include/ -Wno-pointer-sign -fno-strict-overflow -fno-strict-aliasing -fno-common -MMD -U_FORTIFY_SOURCE -include ../../include/linux/kconfig.h   -c -o vringh_test.o vringh_test.c
In file included from ./linux/uio.h:3,
                 from ./linux/../../../include/linux/vringh.h:15,
                 from ./linux/vringh.h:1,
                 from vringh_test.c:9:
./linux/../../../include/linux/uio.h:10:10: fatal error: linux/mm_types.h: No such file or directory
   10 | #include <linux/mm_types.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
make: *** [<builtin>: vringh_test.o] Error 1

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