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    SubjectRe: [PATCH V3] KVM: arm64: Implement vq_present() as a macro
    On Wed, Jul 03, 2019 at 12:04:11PM +0000, Zhang, Lei wrote:
    > Hi guys,
    >
    > I can't start up KVM guest os with SVE feature with your patch.
    > The error message is
    > qemu-system-aarch64: kvm_init_vcpu failed: Invalid argument.
    >
    > My test enviroment.
    > kernel linux-5.2-rc6
    > qemu [Qemu-devel] [PATCH v2 00/14] target/arm/kvm: enable SVE in guests https://lists.gnu.org/archive/html/qemu-devel/2019-06/msg04945.html
    > KVM start up option
    > -machine virt,gic-version=host,accel=kvm \
    > -cpu host \
    > -machine type=virt \
    > -nographic \
    > -smp 16 \ -m 4096 \
    > -drive if=none,file=/root/image.qcow2,id=hd0,format=qcow2 \
    > -device virtio-blk-device,drive=hd0 \
    > -netdev user,id=mynet0,restrict=off,hostfwd=tcp::38001-:22 \
    > -device virtio-net-device,netdev=mynet0 \
    > -bios /root/QEMU_EFI.fd
    >
    > sve_vq_available function's return value' type is bool.
    > But vq_present is macro, so the value is not only TRUE, FALSE but also some numbers.
    > So It failed at
    > if (vq_present(vqs, vq) != sve_vq_available(vq)).
    > I think it is nessary to make vq_present macro's value only TRUE and FALSE.
    >
    > arch/arm64/kvm/guest.c
    > static int set_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
    > for (vq = SVE_VQ_MIN; vq <= max_vq; ++vq)
    > if (vq_present(vqs, vq) != sve_vq_available(vq)) // It failed at here.
    > return -EINVAL;
    >
    > My patch as follows.
    > I have started up KVM guest os successfully with SVE feature with this patch.
    >
    > Could you review and merge my patch?

    [...]

    Thanks for reporting this! It looks like we didn't realise we dropped
    the implicit cast to bool when the result was returned from the original
    version of vq_present().

    Your fix looks sensible to me.

    For the future, see Documentation/process/submitting-patches.rst for
    guidance on how to prepare a patch for submission.

    However, due to the fact that we're already at -rc7 I've written a
    commit message for the patch and reposted [1]. Since the fix is yours,
    I'll keep your authorship and S-o-B.

    Please retest when you can (though the diff should be the same).

    Note, your mail seems to be corrupted, but since the diff is a one-line
    fix, I'm pretty confident I decoded it correctly. If anything looks
    wrong, please let me know.

    [...]

    Cheers
    ---Dave


    [1] [PATCH] KVM: arm64/sve: Fix vq_present() macro to yield a bool
    http://lists.infradead.org/pipermail/linux-arm-kernel/2019-July/664745.html

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