diff options
Diffstat (limited to 'hw/virtio/virtio-pci.c')
| -rw-r--r-- | hw/virtio/virtio-pci.c | 45 |
1 files changed, 28 insertions, 17 deletions
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c index ddb5da181c..f5608140f9 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); @@ -314,12 +311,14 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) 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->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG; + /* Linux before 2.6.34 drives the device without enabling + the PCI device bus master bit. Enable it automatically + for the guest. This is a PCI spec violation but so is + initiating DMA with bus master bit clear. */ + if (val == (VIRTIO_CONFIG_S_ACKNOWLEDGE | VIRTIO_CONFIG_S_DRIVER)) { + pci_default_write_config(&proxy->pci_dev, PCI_COMMAND, + proxy->pci_dev.config[PCI_COMMAND] | + PCI_COMMAND_MASTER, 1); } break; case VIRTIO_MSI_CONFIG_VECTOR: @@ -470,13 +469,18 @@ static void virtio_write_config(PCIDevice *pci_dev, uint32_t address, VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev); VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus); + uint8_t cmd = proxy->pci_dev.config[PCI_COMMAND]; + 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)) { + (cmd & PCI_COMMAND_MASTER)) { + /* Bus driver disables bus mastering - make it act + * as a kind of reset to render the device quiescent. */ virtio_pci_stop_ioeventfd(proxy); - virtio_set_status(vdev, vdev->status & ~VIRTIO_CONFIG_S_DRIVER_OK); + virtio_reset(vdev); + msix_unuse_all_vectors(&proxy->pci_dev); } } @@ -885,11 +889,19 @@ 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) && - !(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { - proxy->flags |= VIRTIO_PCI_FLAG_BUS_MASTER_BUG; + /* Linux before 2.6.34 drives the device without enabling + the PCI device bus master bit. Enable it automatically + for the guest. This is a PCI spec violation but so is + initiating DMA with bus master bit clear. + Note: this only makes a difference when migrating + across QEMU versions from an old QEMU, as for new QEMU + bus master and driver bits are always in sync. + TODO: consider enabling conditionally for compat machine types. */ + if (vdev->status & (VIRTIO_CONFIG_S_ACKNOWLEDGE | + VIRTIO_CONFIG_S_DRIVER)) { + 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 { @@ -1030,7 +1042,6 @@ 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[] = { |