On Thu, Sep 11, 2014 at 06:45:33PM +0200, Greg Kurz wrote:
> From: Michael S. Tsirkin <m...@redhat.com>
>
> commit cc943c36faa192cd4b32af8fe5edb31894017d35
> pci: Use bus master address space for delivering MSI/MSI-X messages
> breaks virtio-net for rhel6.[56] x86 guests because they don't
> enable bus mastering for virtio PCI devices. For the same reason,
> rhel6.[56] ppc64 guests cannot boot on a virtio-blk disk anymore.
>
> Old guests forgot to enable bus mastering, enable it automatically on
> DRIVER (ppc64 guests may never reach DRIVER_OK). We also need to prevent
> these old guests to disable bus mastering (this happens when the driver
> probes the device). And we must also re-enable bus mastering after migration.
>
> Cc: qemu-sta...@nongnu.org
> Reported-by: Greg Kurz <gk...@linux.vnet.ibm.com>
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
> [ old guest detection on DRIVER,
> squashed patch from Michael S. Tsirkin to re-enable bus mastering,
> Greg Kurz <gk...@linux.vnet.ibm.com> ]
> Tested-by: Cedric Le Goater <c...@fr.ibm.com>
> Signed-off-by: Greg Kurz <gk...@linux.vnet.ibm.com>
I think this is too fragile. Let's try to figure out a strategy
that does not depend on VIRTIO_PCI_FLAG_BUS_MASTER_BUG.
> ---
> hw/virtio/virtio-pci.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index ddb5da1..f981841 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -317,9 +317,11 @@ static void virtio_ioport_write(void *opaque, uint32_t
> addr, uint32_t val)
> /* 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) &&
> + if ((val & VIRTIO_CONFIG_S_DRIVER) &&
> !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> +
> memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
> + true);
> }
> break;
> case VIRTIO_MSI_CONFIG_VECTOR:
> @@ -473,10 +475,14 @@ 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)) {
> - virtio_pci_stop_ioeventfd(proxy);
> - virtio_set_status(vdev, vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK);
> + !(pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> + if (proxy->flags & VIRTIO_PCI_FLAG_BUS_MASTER_BUG) {
> +
> memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
> + true);
> + } else {
> + virtio_pci_stop_ioeventfd(proxy);
> + virtio_set_status(vdev, vdev->status &
> ~VIRTIO_CONFIG_S_DRIVER_OK);
> + }
> }
> }
>
> @@ -890,6 +896,8 @@ static void virtio_pci_vmstate_change(DeviceState *d,
> bool running)
> if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
> !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
> proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG;
> +
> memory_region_set_enabled(&proxy->pci_dev.bus_master_enable_region,
> + true);
> }
> virtio_pci_start_ioeventfd(proxy);
> } else {
