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Don't check for bus master for old guests

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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 <agraf@suse.de>
CC: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Alexander Graf 2010-03-16 19:18:07 +01:00 committed by Anthony Liguori
parent f3571b1a5b
commit c81131db15
1 changed files with 24 additions and 1 deletions
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25
hw/virtio-pci.c
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@ -79,6 +79,10 @@
* 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.
@ -90,6 +94,7 @@
typedef struct {
PCIDevice pci_dev;
VirtIODevice *vdev;
uint32_t bugs;
uint32_t addr;
uint32_t class_code;
uint32_t nvectors;
@ -144,6 +149,13 @@ 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) &&
!(proxy->pci_dev.config[PCI_COMMAND] & PCI_COMMAND_MASTER)) {
proxy->bugs |= VIRTIO_PCI_BUG_BUS_MASTER;
}
return 0;
}
@ -168,6 +180,7 @@ 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)
@ -211,6 +224,14 @@ 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);
@ -377,7 +398,9 @@ 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)) {
proxy->vdev->status &= ~VIRTIO_CONFIG_S_DRIVER_OK;
}
}
}