On Thu, Feb 02, 2023 at 01:51:28PM +0100, Juan Quintela wrote:
> Daniel P. Berrangé <berra...@redhat.com> wrote:
> > On Thu, Feb 02, 2023 at 01:22:12PM +0100, Juan Quintela wrote:
> >> "manish.mishra" <manish.mis...@nutanix.com> wrote:
> >> > MSG_PEEK peeks at the channel, The data is treated as unread and
> >> > the next read shall still return this data. This support is
> >> > currently added only for socket class. Extra parameter 'flags'
> >> > is added to io_readv calls to pass extra read flags like MSG_PEEK.
> >> >
> >> > Reviewed-by: Peter Xu <pet...@redhat.com>
> >> > Reviewed-by: Daniel P. Berrange <berra...@redhat.com>
> >> > Suggested-by: Daniel P. Berrange <berra...@redhat.com>
> >> > Signed-off-by: manish.mishra <manish.mis...@nutanix.com>
> >>
> >>
> >> This change breaks RDMA migration.
> >>
> >> FAILED: libcommon.fa.p/migration_rdma.c.o
> >> cc -m64 -mcx16 -Ilibcommon.fa.p -I/usr/include/pixman-1
> >> -I/usr/include/libpng16 -I/usr/include/spice-server -I/usr/include/spice-1
> >> -I/usr/include/cacard -I/usr/include/glib-2.0
> >> -I/usr/lib64/glib-2.0/include -I/usr/include/sysprof-4 -I/usr/include/nss3
> >> -I/usr/include/nspr4 -I/usr/include/PCSC -I/usr/include/p11-kit-1
> >> -I/usr/include/libusb-1.0 -I/usr/include/SDL2 -I/usr/include/libmount
> >> -I/usr/include/blkid -I/usr/include/gio-unix-2.0 -I/usr/include/slirp
> >> -fdiagnostics-color=auto -Wall -Winvalid-pch -Werror -std=gnu11 -O2 -g
> >> -isystem /mnt/code/qemu/full/linux-headers -isystem linux-headers -iquote
> >> . -iquote /mnt/code/qemu/full -iquote /mnt/code/qemu/full/include -iquote
> >> /mnt/code/qemu/full/tcg/i386 -pthread -U_FORTIFY_SOURCE
> >> -D_FORTIFY_SOURCE=2 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64
> >> -D_LARGEFILE_SOURCE -fno-strict-aliasing -fno-common -fwrapv -Wundef
> >> -Wwrite-strings -Wmissing-prototypes -Wstrict-prototypes -Wredundant-decls
> >> -Wold-style-declaration -Wold-style-definition -Wtype-limits
> >> -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers
> >> -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined
> >> -Wimplicit-fallthrough=2 -Wmissing-format-attribute
> >> -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi
> >> -fstack-protector-strong -fPIE -D_REENTRANT -Wno-undef
> >> -DSTRUCT_IOVEC_DEFINED -MD -MQ libcommon.fa.p/migration_rdma.c.o -MF
> >> libcommon.fa.p/migration_rdma.c.o.d -o libcommon.fa.p/migration_rdma.c.o
> >> -c ../../../../mnt/code/qemu/full/migration/rdma.c
> >> ../../../../mnt/code/qemu/full/migration/rdma.c: In function
> >> ‘qio_channel_rdma_class_init’:
> >> ../../../../mnt/code/qemu/full/migration/rdma.c:4020:25: error: assignment
> >> to ‘ssize_t (*)(QIOChannel *, const struct iovec *, size_t, int **,
> >> size_t *, int, Error **)’ {aka ‘long int (*)(QIOChannel *, const struct
> >> iovec *, long unsigned int, int **, long unsigned int *, int, Error
> >> **)’} from incompatible pointer type ‘ssize_t (*)(QIOChannel *, const
> >> struct iovec *, size_t, int **, size_t *, Error **)’ {aka ‘long int
> >> (*)(QIOChannel *, const struct iovec *, long unsigned int, int **, long
> >> unsigned int *, Error **)’} [-Werror=incompatible-pointer-types]
> >> 4020 | ioc_klass->io_readv = qio_channel_rdma_readv;
> >> | ^
> >> cc1: all warnings being treated as errors
> >>
> >> And I don't really know how to fix it, because the problem is that rdma
> >> don't use qio_channel_readv_full() at all.
> >
> > Likely qio_channel_rdma_readv just adds the 'int flags' param added.
> > It doesn't need to actually do anything with the flags as they are
> > checked before
>
> I can do that. That would fix the compilation issue.
>
> But will rdma work? Because it fakes a qio channel, so what is going to
> implement the MSG_PEEK functionality for it? It don't end calling
> recv() at all.
It is no problem - the qio_channel_readv method changes in this patch
add:
+ if ((flags & QIO_CHANNEL_READ_FLAG_MSG_PEEK) &&
+ !qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_READ_MSG_PEEK)) {
+ error_setg_errno(errp, EINVAL,
+ "Channel does not support peek read");
+ return -1;
+ }
so it is impossible for qio_channel_rdma_readv to be invoked with
flags having MSG_PEEK set, thus RDMA can ignore the whole concept.
With regards,
Daniel
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