On Mon, Oct 13, 2014 at 10:49:41AM +0200, Greg Kurz wrote:
> On Mon, 6 Oct 2014 20:25:04 +0300
> "Michael S. Tsirkin" <m...@redhat.com> wrote:
> > [...]
> >
> > BTW I reverted that patch, and to fix migration, I'm thinking
> > about applying the following patch on top of master.
> >
>
> Michael,
>
> I could force the migration issue with a rhel65 guest thanks to the
> following patch, applied to hw/virtio/virtio-pci.c in QEMU v2.1.
>
> @@ -271,6 +272,16 @@ static void virtio_ioport_write(void *opaque, uint32_t
> addr, uint32_t val)
> VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> hwaddr pa;
>
> + if ((vdev->status == (VIRTIO_CONFIG_S_ACKNOWLEDGE |
> VIRTIO_CONFIG_S_DRIVER))
> + && (!(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER))
> + && getenv("MIG_BUG"))
> + {
> + fprintf(stderr, "\n\n\n\tMIGRATE !\n\n\n");
> + qmp_migrate(getenv("MIG_BUG"), false, false, false, false, false,
> + false, NULL);
> + unsetenv("MIG_BUG");
> + }
> +
> switch (addr) {
> case VIRTIO_PCI_GUEST_FEATURES:
> /* Guest does not negotiate properly? We have to assume nothing. */
>
>
> Indeed, the destination QEMU master hangs because bus master isn't set.
>
> > Would appreciate testing cross-version migration (2.1 to master)
> > with this patch applied.
> >
>
> I had first to to enable the property for pseries of course. I could then
> migrate QEMU v2.1 to QEMU master and back to QEMU v2.1, in the window
> where we have DRIVER enabled and MASTER disabled, without experiencing
> the hang.
>
> Your fix works as expected (just a remark below).
>
> >
> >
> > diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> > index 1cea157..8873b6d 100644
> > --- a/hw/virtio/virtio-pci.h
> > +++ b/hw/virtio/virtio-pci.h
> > @@ -53,6 +53,11 @@ typedef struct VirtioBusClass VirtioPCIBusClass;
> > #define VIRTIO_PCI_BUS_CLASS(klass) \
> > OBJECT_CLASS_CHECK(VirtioPCIBusClass, klass, TYPE_VIRTIO_PCI_BUS)
> >
> > +/* Need to activate work-arounds for buggy guests at vmstate load. */
> > +#define VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT 0
> > +#define VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION \
> > + (1 << VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT)
> > +
> > /* Performance improves when virtqueue kick processing is decoupled from
> > the
> > * vcpu thread using ioeventfd for some devices. */
> > #define VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT 1
> > diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> > index bae023a..e07b6c4 100644
> > --- a/include/hw/i386/pc.h
> > +++ b/include/hw/i386/pc.h
> > @@ -312,6 +312,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *,
> > uint64_t *);
> > .driver = "intel-hda",\
> > .property = "old_msi_addr",\
> > .value = "on",\
> > + },\
> > + {\
> > + .driver = "virtio-pci",\
> > + .property = "virtio-pci-bus-master-bug-migration",\
> > + .value = "on",\
> > }
> >
> > #define PC_COMPAT_2_0 \
>
> FWIW, the issue does not occur with intel targets, at least not
> in my test case (booting rhel6 on a virtio-blk disk). I see bus
> master is set early (bios ?) and never unset...
>
> If you decide to apply for intel anyway, shouldn't the enablement be
> in a separate patch ?
>
> Will you resend or would you like me to do it, along with the pseries
> enablement part ? In this case, I would need your SoB for the present
> patch.
>
> Thanks.
>
> --
> Greg
AFAIK pseries doesn't support cross-version migration, does it?
> > diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> > index a827cd4..a499a3c 100644
> > --- a/hw/virtio/virtio-pci.c
> > +++ b/hw/virtio/virtio-pci.c
> > @@ -86,9 +86,6 @@
> > * 12 is historical, and due to x86 page size. */
> > #define VIRTIO_PCI_QUEUE_ADDR_SHIFT 12
> >
> > -/* Flags track per-device state like workarounds for quirks in older
> > guests. */
> > -#define VIRTIO_PCI_FLAG_BUS_MASTER_BUG (1 << 0)
> > -
> > static void virtio_pci_bus_new(VirtioBusState *bus, size_t bus_size,
> > VirtIOPCIProxy *dev);
> >
> > @@ -323,14 +320,6 @@ static void virtio_ioport_write(void *opaque, uint32_t
> > addr, uint32_t val)
> > proxy->pci_dev.config[PCI_COMMAND] |
> > PCI_COMMAND_MASTER, 1);
> > }
> > -
> > - /* Linux before 2.6.34 sets the device as OK without enabling
> > - the PCI device bus master bit. In this case we need to disable
> > - some safety checks. */
> > - if ((val & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > - !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> > - proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> > - }
> > break;
> > case VIRTIO_MSI_CONFIG_VECTOR:
> > msix_vector_unuse(&proxy->pci_dev, vdev->config_vector);
> > @@ -483,8 +472,7 @@ static void virtio_write_config(PCIDevice *pci_dev,
> > uint32_t address,
> > pci_default_write_config(pci_dev, address, val, len);
> >
> > if (range_covers_byte(address, len, PCI_COMMAND) &&
> > - !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER) &&
> > - !(proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG)) {
> > + !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> > virtio_pci_stop_ioeventfd(proxy);
> > virtio_set_status(vdev, vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK);
> > }
> > @@ -895,11 +883,15 @@ static void virtio_pci_vmstate_change(DeviceState *d,
> > bool running)
> > VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> >
> > if (running) {
> > - /* Try to find out if the guest has bus master disabled, but is
> > - in ready state. Then we have a buggy guest OS. */
> > - if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> > + /* Old QEMU versions did not set bus master enable on status write.
> > + * Detect DRIVER set and enable it.
> > + */
> > + if ((proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION) &&
> > + (vdev->status & VIRTIO_CONFIG_S_DRIVER) &&
> > !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> > - proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> > + pci_default_write_config(&proxy->pci_dev, PCI_COMMAND,
> > + proxy->pci_dev.config[PCI_COMMAND] |
> > + PCI_COMMAND_MASTER, 1);
> > }
> > virtio_pci_start_ioeventfd(proxy);
> > } else {
> > @@ -1040,10 +1032,11 @@ static void virtio_pci_reset(DeviceState *qdev)
> > virtio_pci_stop_ioeventfd(proxy);
> > virtio_bus_reset(bus);
> > msix_unuse_all_vectors(&proxy->pci_dev);
> > - proxy->flags &= ~VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> > }
> >
> > static Property virtio_pci_properties[] = {
> > + DEFINE_PROP_BIT("virtio-pci-bus-master-bug-migration", VirtIOPCIProxy,
> > flags,
> > + VIRTIO_PCI_FLAG_BUS_MASTER_BUG_MIGRATION_BIT, false),
> > DEFINE_VIRTIO_COMMON_FEATURES(VirtIOPCIProxy, host_features),
> > DEFINE_PROP_END_OF_LIST(),
> > };
> >
