On 09/10/2014 08:35 AM, Greg Kurz wrote:
> On Mon, 8 Sep 2014 19:05:02 +0300
> "Michael S. Tsirkin" <m...@redhat.com> wrote:
>
>> 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
>>
>> Old guests forgot to enable bus mastering, enable it
>> automatically on DRIVER_OK.
>>
>> Note: we should either back out the original patch from
>> stable or apply this one on top.
>>
>> Cc: qemu-sta...@nongnu.org
>> Reported-by: Greg Kurz <gk...@linux.vnet.ibm.com>
>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
>> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
>> ---
>> hw/virtio/virtio-pci.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
>> index ddb5da1..af937d2 100644
>> --- a/hw/virtio/virtio-pci.c
>> +++ b/hw/virtio/virtio-pci.c
>> @@ -320,6 +320,8 @@ static void virtio_ioport_write(void *opaque, uint32_t
>> addr, uint32_t val)
>> if ((val & 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);
>> }
>> break;
>> case VIRTIO_MSI_CONFIG_VECTOR:
>
> Cc'ing Alexey for some SLOF and early boot of the ppc64 kernel expertise.
Cc'ing Nikunj - he is SLOF expert.
I cannot comment - I have no idea what VIRTIO_PCI_FLAG_BUS_MASTER_BUG does.
>
> Michael,
>
> This was enough to fix virtio-net in the rhel6.5 x86 guest case.
> Unfortunately,
> this fails for rhel6.5 ppc64 because it is never called... I did some
> debugging:
> it looks like the guest kernel calls the OF quisece call to flush pending DMA
> and disables bus master on the virtio-blk device (PCI_COMMAND == 0x3). The
> guest then continues to boot and hangs... It appears that waiting for the
> guest to issue VIRTIO_CONFIG_S_DRIVER_OK is not enough. Since we need this for
> MSI to work, I tried the following and it fixes the issue:
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index af937d2..3d72aa8 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -111,9 +111,14 @@ static void virtio_pci_notify(DeviceState *d, uint16_t
> vector)
> {
> VirtIOPCIProxy *proxy = to_virtio_pci_proxy_fast(d);
>
> - if (msix_enabled(&proxy->pci_dev))
> + if (msix_enabled(&proxy->pci_dev)) {
> + if (!(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);
> + }
> msix_notify(&proxy->pci_dev, vector);
> - else {
> + } else {
> VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> pci_set_irq(&proxy->pci_dev, vdev->isr & 1);
> }
>
> If this is acceptable, I'll make it a helper and squash it into your patch.
>
> Thoughts ?
>
--
Alexey
