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Re: [PULL v4 42/83] virtio-rng-pci: Allow setting nvectors, so we can us
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PULL v4 42/83] virtio-rng-pci: Allow setting nvectors, so we can use MSI-X |
Date: |
Mon, 9 Jan 2023 10:43:37 +0000 |
User-agent: |
Mutt/2.2.9 (2022-11-12) |
* Michael S. Tsirkin (mst@redhat.com) wrote:
> On Mon, Jan 09, 2023 at 10:20:45AM +0000, Dr. David Alan Gilbert wrote:
> > * Michael S. Tsirkin (mst@redhat.com) wrote:
> > > From: David Daney <david.daney@fungible.com>
> > >
> > > Most other virtio-pci devices allow MSI-X, let's have it for rng too.
> > >
> > > Signed-off-by: David Daney <david.daney@fungible.com>
> > > Reviewed-by: Marcin Nowakowski <marcin.nowakowski@fungible.com>
> > > Signed-off-by: Philippe Mathieu-Daudé <philmd@fungible.com>
> > > Message-Id: <20221014160947.66105-1-philmd@fungible.com>
> > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> > > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> >
> > This breaks migration compatibility 7.1->7.2 :
> >
> > (qemu) qemu: get_pci_config_device: Bad config data: i=0x34 read: 84
> > device: 98 cmask: ff wmask: 0 w1cmask:0
> > qemu: Failed to load PCIDevice:config
> > qemu: Failed to load virtio-rng:virtio
> > qemu: error while loading state for instance 0x0 of device
> > '0000:00:03.0/virtio-rng'
> > qemu: load of migration failed: Invalid argument
> >
> > because the destination is configured with msi-x but the source isn't.
> >
> > The fix is in theory simple:
> > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > index f589b92909..45459d1cef 100644
> > --- a/hw/core/machine.c
> > +++ b/hw/core/machine.c
> > @@ -45,6 +45,7 @@ const size_t hw_compat_7_2_len =
> > G_N_ELEMENTS(hw_compat_7_2);
> >
> > GlobalProperty hw_compat_7_1[] = {
> > { "virtio-device", "queue_reset", "false" },
> > + { "virtio-rng-pci", "vectors", "0" },
> > };
> > const size_t hw_compat_7_1_len = G_N_ELEMENTS(hw_compat_7_1);
> >
> > the gotcha is that will break 7.2->7.2-fixed.
> >
> > (I guess you can also work around it by explicitly passing vectors=0 to
> > the virtio-rng on the cli)
> >
> > Does anyone have preferences as to whether that should be fixed in the
> > 7.2 world or left as is?
> >
> > This is:
> > https://bugzilla.redhat.com/show_bug.cgi?id=2155749
> >
> > Dave
>
> I think that yes, it should be fixed in 7.2.
OK, I'll resend that as a patch in a mo.
Dave
>
> > > ---
> > > hw/virtio/virtio-rng-pci.c | 14 ++++++++++++++
> > > 1 file changed, 14 insertions(+)
> > >
> > > diff --git a/hw/virtio/virtio-rng-pci.c b/hw/virtio/virtio-rng-pci.c
> > > index 151ece6f94..6e76f8b57b 100644
> > > --- a/hw/virtio/virtio-rng-pci.c
> > > +++ b/hw/virtio/virtio-rng-pci.c
> > > @@ -13,6 +13,7 @@
> > >
> > > #include "hw/virtio/virtio-pci.h"
> > > #include "hw/virtio/virtio-rng.h"
> > > +#include "hw/qdev-properties.h"
> > > #include "qapi/error.h"
> > > #include "qemu/module.h"
> > > #include "qom/object.h"
> > > @@ -31,11 +32,23 @@ struct VirtIORngPCI {
> > > VirtIORNG vdev;
> > > };
> > >
> > > +static Property virtio_rng_properties[] = {
> > > + DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags,
> > > + VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
> > > + DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors,
> > > + DEV_NVECTORS_UNSPECIFIED),
> > > + DEFINE_PROP_END_OF_LIST(),
> > > +};
> > > +
> > > static void virtio_rng_pci_realize(VirtIOPCIProxy *vpci_dev, Error
> > > **errp)
> > > {
> > > VirtIORngPCI *vrng = VIRTIO_RNG_PCI(vpci_dev);
> > > DeviceState *vdev = DEVICE(&vrng->vdev);
> > >
> > > + if (vpci_dev->nvectors == DEV_NVECTORS_UNSPECIFIED) {
> > > + vpci_dev->nvectors = 2;
> > > + }
> > > +
> > > if (!qdev_realize(vdev, BUS(&vpci_dev->bus), errp)) {
> > > return;
> > > }
> > > @@ -54,6 +67,7 @@ static void virtio_rng_pci_class_init(ObjectClass
> > > *klass, void *data)
> > > pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_RNG;
> > > pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
> > > pcidev_k->class_id = PCI_CLASS_OTHERS;
> > > + device_class_set_props(dc, virtio_rng_properties);
> > > }
> > >
> > > static void virtio_rng_initfn(Object *obj)
> > > --
> > > MST
> > >
> > >
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK