Re: [PATCH RFC v2 00/13] virtio: introduce support for GSO over UDP tunnel

[Lei Yang <leiyang@redhat.com>]

On Mon, Jul 14, 2025 at 5:05 PM Paolo Abeni <pabeni@redhat.com> wrote:
>
> On 7/14/25 10:43 AM, Lei Yang wrote:
> > Does the compile of this series of patches require support for a
> > special kernel environment? I hit a compile issue after applied you
> > patches:
> > [1440/2928] Compiling C object libsystem.a.p/hw_virtio_vhost.c.o
> > FAILED: libsystem.a.p/hw_virtio_vhost.c.o
> > cc -m64 -Ilibsystem.a.p -I. -I.. -Isubprojects/dtc/libfdt
> > -I../subprojects/dtc/libfdt -Isubprojects/libvduse
> > -I../subprojects/libvduse -Iui -Iqapi -Itrace -Iui/shader
> > -I/usr/include/pixman-1 -I/usr/include/glib-2.0
> > -I/usr/lib64/glib-2.0/include -I/usr/include/libmount
> > -I/usr/include/blkid -I/usr/include/sysprof-6
> > -I/usr/include/gio-unix-2.0 -I/usr/include/slirp
> > -fdiagnostics-color=auto -Wall -Winvalid-pch -Werror -std=gnu11 -O0 -g
> > -fstack-protector-strong -Wempty-body -Wendif-labels
> > -Wexpansion-to-defined -Wformat-security -Wformat-y2k
> > -Wignored-qualifiers -Wimplicit-fallthrough=2 -Winit-self
> > -Wmissing-format-attribute -Wmissing-prototypes -Wnested-externs
> > -Wold-style-declaration -Wold-style-definition -Wredundant-decls
> > -Wshadow=local -Wstrict-prototypes -Wtype-limits -Wundef -Wvla
> > -Wwrite-strings -Wno-missing-include-dirs -Wno-psabi
> > -Wno-shift-negative-value -isystem
> > /mnt/tests/distribution/command/qemu/linux-headers -isystem
> > linux-headers -iquote . -iquote /mnt/tests/distribution/command/qemu
> > -iquote /mnt/tests/distribution/command/qemu/include -iquote
> > /mnt/tests/distribution/command/qemu/host/include/x86_64 -iquote
> > /mnt/tests/distribution/command/qemu/host/include/generic -iquote
> > /mnt/tests/distribution/command/qemu/tcg/i386 -pthread -mcx16 -msse2
> > -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
> > -fno-strict-aliasing -fno-common -fwrapv -ftrivial-auto-var-init=zero
> > -fzero-call-used-regs=used-gpr -fPIE -DWITH_GZFILEOP -DCONFIG_SOFTMMU
> > -DCOMPILING_SYSTEM_VS_USER -MD -MQ libsystem.a.p/hw_virtio_vhost.c.o
> > -MF libsystem.a.p/hw_virtio_vhost.c.o.d -o
> > libsystem.a.p/hw_virtio_vhost.c.o -c ../hw/virtio/vhost.c
> > ../hw/virtio/vhost.c: In function ‘vhost_dev_set_features’:
> > ../hw/virtio/vhost.c:38:9: error: ‘r’ may be used uninitialized
> > [-Werror=maybe-uninitialized]
> >    38 |         error_report(fmt ": %s (%d)", ## __VA_ARGS__, \
> >       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    39 |                      strerror(-retval), -retval); \
> >       |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ../hw/virtio/vhost.c:1006:9: note: in expansion of macro ‘VHOST_OPS_DEBUG’
> >  1006 |         VHOST_OPS_DEBUG(r, "extended features without device support");
> >       |         ^~~~~~~~~~~~~~~
> > ../hw/virtio/vhost.c:989:9: note: ‘r’ was declared here
> >   989 |     int r;
> >       |         ^
> > cc1: all warnings being treated as errors
> > ninja: build stopped: subcommand failed.
> > make[1]: *** [Makefile:168: run-ninja] Error 1
> > make[1]: Leaving directory '/mnt/tests/distribution/command/qemu/build'
> > make[1]: Entering directory '/mnt/tests/distribution/command/qemu/build'
> > [1/1493] Generating subprojects/dtc/version_gen.h with a custom command
> > [2/1493] Generating qemu-version.h with a custom command (wrapped by
> > meson to capture output)
> > [3/1492] Compiling C object libsystem.a.p/hw_virtio_vhost.c.o
> > FAILED: libsystem.a.p/hw_virtio_vhost.c.o
> > cc -m64 -Ilibsystem.a.p -I. -I.. -Isubprojects/dtc/libfdt
> > -I../subprojects/dtc/libfdt -Isubprojects/libvduse
> > -I../subprojects/libvduse -Iui -Iqapi -Itrace -Iui/shader
> > -I/usr/include/pixman-1 -I/usr/include/glib-2.0
> > -I/usr/lib64/glib-2.0/include -I/usr/include/libmount
> > -I/usr/include/blkid -I/usr/include/sysprof-6
> > -I/usr/include/gio-unix-2.0 -I/usr/include/slirp
> > -fdiagnostics-color=auto -Wall -Winvalid-pch -Werror -std=gnu11 -O0 -g
> > -fstack-protector-strong -Wempty-body -Wendif-labels
> > -Wexpansion-to-defined -Wformat-security -Wformat-y2k
> > -Wignored-qualifiers -Wimplicit-fallthrough=2 -Winit-self
> > -Wmissing-format-attribute -Wmissing-prototypes -Wnested-externs
> > -Wold-style-declaration -Wold-style-definition -Wredundant-decls
> > -Wshadow=local -Wstrict-prototypes -Wtype-limits -Wundef -Wvla
> > -Wwrite-strings -Wno-missing-include-dirs -Wno-psabi
> > -Wno-shift-negative-value -isystem
> > /mnt/tests/distribution/command/qemu/linux-headers -isystem
> > linux-headers -iquote . -iquote /mnt/tests/distribution/command/qemu
> > -iquote /mnt/tests/distribution/command/qemu/include -iquote
> > /mnt/tests/distribution/command/qemu/host/include/x86_64 -iquote
> > /mnt/tests/distribution/command/qemu/host/include/generic -iquote
> > /mnt/tests/distribution/command/qemu/tcg/i386 -pthread -mcx16 -msse2
> > -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE
> > -fno-strict-aliasing -fno-common -fwrapv -ftrivial-auto-var-init=zero
> > -fzero-call-used-regs=used-gpr -fPIE -DWITH_GZFILEOP -DCONFIG_SOFTMMU
> > -DCOMPILING_SYSTEM_VS_USER -MD -MQ libsystem.a.p/hw_virtio_vhost.c.o
> > -MF libsystem.a.p/hw_virtio_vhost.c.o.d -o
> > libsystem.a.p/hw_virtio_vhost.c.o -c ../hw/virtio/vhost.c
> > ../hw/virtio/vhost.c: In function ‘vhost_dev_set_features’:
> > ../hw/virtio/vhost.c:38:9: error: ‘r’ may be used uninitialized
> > [-Werror=maybe-uninitialized]
> >    38 |         error_report(fmt ": %s (%d)", ## __VA_ARGS__, \
> >       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >    39 |                      strerror(-retval), -retval); \
> >       |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ../hw/virtio/vhost.c:1006:9: note: in expansion of macro ‘VHOST_OPS_DEBUG’
> >  1006 |         VHOST_OPS_DEBUG(r, "extended features without device support");
> >       |         ^~~~~~~~~~~~~~~
> > ../hw/virtio/vhost.c:989:9: note: ‘r’ was declared here
> >   989 |     int r;
> >       |         ^
> > cc1: all warnings being treated as errors
> > ninja: build stopped: subcommand failed.
> > make[1]: *** [Makefile:168: run-ninja] Error 1
> > make[1]: Leaving directory '/mnt/tests/distribution/command/qemu/build'
>
> Thank you for reporting the problem.
>
> No special kernel requirement to build the series, the above is just a
> gross mistake on my side in patch 7/13. If you want to test the series,
> please apply incrementally the following diff.
>
> What baffles me is that gcc 14.3.1 and 11.5.0 are not raising the
> warning (that looks legit/correct) here.
>
> I'll fix the above in the next revision.
>
> Note that you need a running kernel based on current net-next tree in
> both the hypervisor and the guest to actually leverage the new feature.

Ok, I will test this series again and update the test results.

Thanks
Lei
>
> Thanks,
>
> Paolo
> ---
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 2eee9b0886..c4eab5ce08 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1003,8 +1003,8 @@ static int vhost_dev_set_features(struct vhost_dev
> *dev,
>
>      if (virtio_features_use_extended(features) &&
>          !dev->vhost_ops->vhost_set_features_ex) {
> -        VHOST_OPS_DEBUG(r, "extended features without device support");
>          r = -EINVAL;
> +        VHOST_OPS_DEBUG(r, "extended features without device support");
>          goto out;
>      }
>