On Tue, Mar 16, 2010 at 07:18:07PM +0100, Alexander Graf wrote: > Older Linux guests don't activate the bus master enable bit. So for those we > can just try to be clever and track if they set the DEVICE_OK bit even though > bus mastering is still disabled. > > Under that condition we can disable the windows safety check. With that logic > in place both guests should work just fine. Without PCI hotplug breaks > virtio-net in Linux < 2.6.34 guests. > > Signed-off-by: Alexander Graf <ag...@suse.de> > CC: Michael S. Tsirkin <m...@redhat.com> > --- > hw/virtio-pci.c | 25 ++++++++++++++++++++++++- > 1 files changed, 24 insertions(+), 1 deletions(-) > > diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c > index 3594152..4fc4b3c 100644 > --- a/hw/virtio-pci.c > +++ b/hw/virtio-pci.c > @@ -76,6 +76,10 @@ > * 12 is historical, and due to x86 page size. */ > #define VIRTIO_PCI_QUEUE_ADDR_SHIFT 12 > > +/* We can catch some guest bugs inside here so we continue supporting older > + guests. */ > +#define VIRTIO_PCI_BUG_BUS_MASTER (1 << 0) > + > /* QEMU doesn't strictly need write barriers since everything runs in > * lock-step. We'll leave the calls to wmb() in though to make it obvious > for > * KVM or if kqemu gets SMP support. > @@ -87,6 +91,7 @@ > typedef struct { > PCIDevice pci_dev; > VirtIODevice *vdev; > + uint32_t bugs; > uint32_t addr; > uint32_t class_code; > uint32_t nvectors; > @@ -138,6 +143,13 @@ static int virtio_pci_load_config(void * opaque, > QEMUFile *f) > if (proxy->vdev->config_vector != VIRTIO_NO_VECTOR) { > return msix_vector_use(&proxy->pci_dev, proxy->vdev->config_vector); > } > + > + /* Try to find out if the guest has bus master disabled, but is > + in ready state. Then we have a buggy guest OS. */ > + if (!(proxy->vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) &&
should not this be (proxy->vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)? > + !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { > + proxy->bugs |= VIRTIO_PCI_BUG_BUS_MASTER; > + } > return 0; > } > > @@ -162,6 +174,7 @@ static void virtio_pci_reset(DeviceState *d) > VirtIOPCIProxy *proxy = container_of(d, VirtIOPCIProxy, pci_dev.qdev); > virtio_reset(proxy->vdev); > msix_reset(&proxy->pci_dev); > + proxy->bugs = 0; > } > > static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) > @@ -205,6 +218,14 @@ static void virtio_ioport_write(void *opaque, uint32_t > addr, uint32_t val) > virtio_reset(proxy->vdev); > msix_unuse_all_vectors(&proxy->pci_dev); > } > + > + /* 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->bugs |= VIRTIO_PCI_BUG_BUS_MASTER; > + } > break; > case VIRTIO_MSI_CONFIG_VECTOR: > msix_vector_unuse(&proxy->pci_dev, vdev->config_vector); > @@ -372,7 +393,9 @@ static void virtio_write_config(PCIDevice *pci_dev, > uint32_t address, > > if (PCI_COMMAND == address) { > if (!(val & PCI_COMMAND_MASTER)) { > - proxy->vdev->status &= ~VIRTIO_CONFIG_S_DRIVER_OK; > + if (!(proxy->bugs & VIRTIO_PCI_BUG_BUS_MASTER)) { nested if statements are confusing if (!(val & PCI_COMMAND_MASTER) && !(proxy->bugs & VIRTIO_PCI_BUG_BUS_MASTER)) would be clearer. > + proxy->vdev->status &= ~VIRTIO_CONFIG_S_DRIVER_OK; > + } > } > } > > -- > 1.6.0.2