Re: [PATCH 1/3] Fix libvhost-user.c compilation.

On Fri, Apr 7, 2023 at 11:29 AM David Turner <digit@google.com> wrote:

So it looks like that for some reason, the QEMU linux-headers directory is not in the include search path for this compilation command, and that the system-or-sysroot provided <linux/vhost.h> is picked instead. Fixing this might be a better long-term fix than what I am proposing in this patch. I am not sure how to do that yet though. Do you have any recommendations?

On Fri, Apr 7, 2023 at 11:25 AM David Turner <digit@google.com> wrote:
I meant glibc-2.17, I am using a sysroot to ensure the generated binaries run on older Linux distributions.

On Fri, Apr 7, 2023 at 11:24 AM David Turner <digit@google.com> wrote:
The <linux/vhost.h> of glib-2.17 begins with:

#ifndef _LINUX_VHOST_H
#define _LINUX_VHOST_H
/* Userspace interface for in-kernel virtio accelerators. */
/* vhost is used to reduce the number of system calls involved in virtio.
*
* Existing virtio net code is used in the guest without modification.
*
* This header includes interface used by userspace hypervisor for
* device configuration.
*/
#include <linux/types.h>
#include <linux/ioctl.h>
#include <linux/virtio_config.h>
#include <linux/virtio_ring.h>

See https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.17-4.8/+/refs/heads/master/sysroot/usr/include/linux/vhost.h

Here's the compilation error I get in this case:

FAILED: subprojects/libvhost-user/libvhost-user.a.p/libvhost-user.c.o
/src/prebuilts/clang/clang-r487747/bin/clang --sysroot=/out/sysroot -m64 -mcx16 -Isubprojects/libvhost-user/libvhost-user.a.p -Isubprojects/libvhost-user -I../../
src/third_party/qemu/subprojects/libvhost-user -I/out/dest-install/usr/include -fcolor-diagnostics -Wall -Winvalid-pch -std=gnu99 -O2 -g -Wsign-compare -Wdeclarat
ion-after-statement -Wstrict-aliasing -fno-pie -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing -fno-common -fwrapv -Wundef -Wwrite-strings -Wmissi
ng-prototypes -Wstrict-prototypes -Wredundant-decls -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-b
ody -Wnested-externs -Wendif-labels -Wexpansion-to-defined -Wmissing-format-attribute -Wthread-safety -Wno-initializer-overrides -Wno-missing-include-dirs -Wno-sh
ift-negative-value -Wno-string-plus-int -Wno-typedef-redefinition -Wno-tautological-type-limit-compare -Wno-psabi -Wno-gnu-variable-sized-type-not-at-end -fstack-
protector-strong -pthread -D_GNU_SOURCE -MD -MQ subprojects/libvhost-user/libvhost-user.a.p/libvhost-user.c.o -MF subprojects/libvhost-user/libvhost-user.a.p/libv
host-user.c.o.d -o subprojects/libvhost-user/libvhost-user.a.p/libvhost-user.c.o -c ../../src/third_party/qemu/subprojects/libvhost-user/libvhost-user.c
../../src/third_party/qemu/subprojects/libvhost-user/libvhost-user.c:529:17: error: use of undeclared identifier 'VIRTIO_F_VERSION_1'
1ULL << VIRTIO_F_VERSION_1 |
^
../../src/third_party/qemu/subprojects/libvhost-user/libvhost-user.c:563:30: error: use of undeclared identifier 'VIRTIO_F_VERSION_1'
if (!vu_has_feature(dev, VIRTIO_F_VERSION_1)) {
^
../../src/third_party/qemu/subprojects/libvhost-user/libvhost-user.c:632:22: warning: unused variable 'dev_region' [-Wunused-variable]
VuDevRegion *dev_region = &dev->regions[i];
^
../../src/third_party/qemu/subprojects/libvhost-user/libvhost-user.c:633:13: warning: unused variable 'ret' [-Wunused-variable]
int ret;
^
2 warnings and 2 errors generated.

On Fri, Apr 7, 2023 at 10:03 AM Michael S. Tsirkin <mst@redhat.com> wrote:
If you are reposting, please version patchsets, E.g.
-v2 flag for git format-patch will enerate [PATCH v2] for you.

Repeating what I said on previous version:

On Wed, Apr 05, 2023 at 07:21:07PM +0200, David 'Digit' Turner wrote:
> The source file uses VIRTIO_F_VERSION_1 which is
> not defined by <linux/virtio_config.h> on Debian 10.
>
> The system-provided <linux/virtio_config.h> which
> does not include the macro definition is included
> through <linux/vhost.h>, so fix the issue by including
> the standard-headers version before that.
>
> Signed-off-by: David 'Digit' Turner <digit@google.com>

This happens to work usually but there's no guarantee
"standard-headers/linux/virtio_config.h"
and <linux/virtio_config.h> are interchangeable or
even do not conflict.

But where is <linux/vhost.h> using <linux/virtio_config.h>?
Everyone should be using "standard-headers/linux/virtio_config.h".

> ---
> subprojects/libvhost-user/libvhost-user.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index 0200b78e8e..0a5768cb55 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -32,6 +32,12 @@
> #include <sys/mman.h>
> #include <endian.h>
>
> +/* Necessary to provide VIRTIO_F_VERSION_1 on system
> + * with older linux headers. Must appear before
> + * <linux/vhost.h> below.
> + */
> +#include "standard-headers/linux/virtio_config.h"
> +
> #if defined(__linux__)
> #include <sys/syscall.h>
> #include <fcntl.h>
> --
> 2.40.0.348.gf938b09366-goog

From:	David Turner
Subject:	Re: [PATCH 1/3] Fix libvhost-user.c compilation.
Date:	Fri, 7 Apr 2023 11:47:50 +0200