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Re: [Qemu-devel] [PATCH v2 3/3] virtio-mmio: start ioeventfd when status
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-devel] [PATCH v2 3/3] virtio-mmio: start ioeventfd when status gets DRIVER_OK |
Date: |
Thu, 7 May 2015 15:44:21 +0200 |
On Thu, 07 May 2015 13:51:27 +0300
Pavel Fedin <address@hidden> wrote:
Would it make sense to merge this with the first patch, so that you
introduce ioeventfds in one go?
> Signed-off-by: Ying-Shiuan Pan <address@hidden>
> Signed-off-by: Pavel Fedin <address@hidden>
> ---
> hw/virtio/virtio-mmio.c | 47
> +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 47 insertions(+)
>
> diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
> index 8756240..0ab270d 100644
> --- a/hw/virtio/virtio-mmio.c
> +++ b/hw/virtio/virtio-mmio.c
> @@ -22,6 +22,7 @@
> #include "hw/sysbus.h"
> #include "hw/virtio/virtio.h"
> #include "qemu/host-utils.h"
> +#include "sysemu/kvm.h"
> #include "hw/virtio/virtio-bus.h"
> #include "qemu/error-report.h"
>
> @@ -120,6 +121,43 @@ static int
> virtio_mmio_set_host_notifier_internal(VirtIOMMIOProxy *proxy,
> return r;
> }
>
> +static void virtio_mmio_start_ioeventfd(VirtIOMMIOProxy *proxy)
> +{
> + VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> + int n, r;
> +
> + if (!kvm_eventfds_enabled() ||
> + proxy->ioeventfd_disabled ||
> + proxy->ioeventfd_started) {
> + return;
> + }
> +
> + for (n = 0; n < VIRTIO_PCI_QUEUE_MAX; n++) {
> + if (!virtio_queue_get_num(vdev, n)) {
> + continue;
> + }
> +
> + r = virtio_mmio_set_host_notifier_internal(proxy, n, true, true);
> + if (r < 0) {
> + goto assign_error;
> + }
> + }
> + proxy->ioeventfd_started = true;
> + return;
> +
> +assign_error:
> + while (--n >= 0) {
> + if (!virtio_queue_get_num(vdev, n)) {
> + continue;
> + }
> +
> + r = virtio_mmio_set_host_notifier_internal(proxy, n, false, false);
> + assert(r >= 0);
> + }
> + proxy->ioeventfd_started = false;
> + error_report("%s: failed. Fallback to a userspace (slower).",
> __func__);
> +}
Again, much commonality with pci and ccw, with two differences:
- the check at the beginning of the function (easily factored out)
- ccw disables ioeventfds on failure, pci doesn't and mmio can't as
they don't have a device where they can tack an ioeventfd property bit
on - this means mmio always uses ioeventfds for all devices if
supported, no?
> +
> static void virtio_mmio_stop_ioeventfd(VirtIOMMIOProxy *proxy)
> {
> int r;
> @@ -318,7 +356,16 @@ static void virtio_mmio_write(void *opaque, hwaddr
> offset, uint64_t value,
> virtio_update_irq(vdev);
> break;
> case VIRTIO_MMIO_STATUS:
> + if (!(value & VIRTIO_CONFIG_S_DRIVER_OK)) {
> + virtio_mmio_stop_ioeventfd(proxy);
> + }
> +
> virtio_set_status(vdev, value & 0xff);
> +
> + if (value & VIRTIO_CONFIG_S_DRIVER_OK) {
> + virtio_mmio_start_ioeventfd(proxy);
> + }
> +
> if (vdev->status == 0) {
> virtio_reset(vdev);
> }
Don't you also want to stop the ioeventfd on reset?