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Re: [Qemu-devel] [PATCH] virtio-pci: enable bus master for old guests
From: |
Greg Kurz |
Subject: |
Re: [Qemu-devel] [PATCH] virtio-pci: enable bus master for old guests |
Date: |
Wed, 10 Sep 2014 00:35:32 +0200 |
On Mon, 8 Sep 2014 19:05:02 +0300
"Michael S. Tsirkin" <address@hidden> 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: address@hidden
> Reported-by: Greg Kurz <address@hidden>
> Signed-off-by: Jan Kiszka <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
> 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.
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 ?
--
Gregory Kurz address@hidden
address@hidden
Software Engineer @ IBM/Meiosys http://www.ibm.com
Tel +33 (0)562 165 496
"Anarchy is about taking complete responsibility for yourself."
Alan Moore.
Re: [Qemu-devel] [PATCH] virtio-pci: enable bus master for old guests, Michael S. Tsirkin, 2014/09/10