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    SubjectRe: aio: compat_ioctl issue?
    Jeff Moyer wrote:
    > Michael Tokarev <mjt@tls.msk.ru> writes:
    >
    >> Hello.
    >>
    >> I just come across a situation (next in a long row :)
    >> when on x86, 32bit userspace does not work with 64bit
    >> kernel. This time this is about aio requests.
    >>
    >> An application submits some aio job, and it is returned
    >> immediately (from io_getevents()) with EINVAL error.
    []
    > Can you post the program, please?

    The program which I'm trying is quite big - it's qemu-kvm
    v. 0.12.3 compiled with --enable-linux-aio. I bugged
    kvm folks about non-working aio support but immediately
    realized it's 32/64bit issue in the kernel, since 64bit
    kvm works just fine on the same kernel (which is 64bits).
    So I added 2 printfs into its linux-aio.c and re-run it.

    The diff against upstream qemu-kvm is this one:

    ---- cut -----
    diff --git a/linux-aio.c b/linux-aio.c
    index 5e892b0..e856873 100644
    --- a/linux-aio.c
    +++ b/linux-aio.c
    @@ -60,6 +60,9 @@ static void qemu_laio_process_completion(struct qemu_laio_state *s,

    ret = laiocb->ret;
    if (ret != -ECANCELED) {
    +if (ret != laiocb->nbytes)
    +fprintf(stderr, "io_getevents: exp %d got %d %s\n", laiocb->nbytes, ret,
    +strerror(ret));
    if (ret == laiocb->nbytes)
    ret = 0;
    else if (ret >= 0)
    @@ -223,6 +226,12 @@ BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
    io_set_eventfd(&laiocb->iocb, s->efd);
    s->count++;

    +{ struct iovec *v = (struct iovec*)iocbs->u.c.buf;
    +printf("io_submit: lio_opcode=%d reqprio=%d iov=%p{%p,%d}, niov=%lu, offset=%Ld\n",
    +iocbs->aio_lio_opcode, iocbs->aio_reqprio, iocbs->u.c.buf,
    +v->iov_base, v->iov_len,
    +iocbs->u.c.nbytes, iocbs->u.c.offset);
    +}
    if (io_submit(s->ctx, 1, &iocbs) < 0)
    goto out_dec_count;
    return &laiocb->common;
    ---- cut -----
    I'm not sure if it's useful or not.

    Qemu-kvm git tree is at
    git://git.kernel.org/pub/scm/virt/kvm/qemu-kvm.git

    I never dealt with aio before, so I'll need to familiarize
    myself with it before trying to create a smaller testcase.

    Thanks!

    /mjt


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