On system reset, we currently try to quiesce DMA by clearing the
command register. This assumes that nothing re-enables bus master
support without first de-programming the device. Use a bigger
hammer to help the guest not shoot itself by issuing a function
reset via sysfs on each system reset.
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
hw/device-assignment.c | 24 ++++++++++++++++++++++--
1 files changed, 22 insertions(+), 2 deletions(-)
diff --git a/hw/device-assignment.c b/hw/device-assignment.c
index db82e73..f1c2a3c 100644
--- a/hw/device-assignment.c
+++ b/hw/device-assignment.c
@@ -1693,13 +1693,33 @@ static const VMStateDescription vmstate_assigned_device = {
static void reset_assigned_device(DeviceState *dev)
{
- PCIDevice *d = DO_UPCAST(PCIDevice, qdev, dev);
+ PCIDevice *pci_dev = DO_UPCAST(PCIDevice, qdev, dev);
+ AssignedDevice *adev = DO_UPCAST(AssignedDevice, dev, pci_dev);
+ char reset_file[64];
+ const char reset[] = "1";
+ int fd, ret;
+
+ snprintf(reset_file, sizeof(reset_file),
+ "/sys/bus/pci/devices/0000:%02x:%02x.%01x/reset",
+ adev->host.bus, adev->host.dev, adev->host.func);
+
+ /*
+ * Issue a device reset via pci-sysfs. Note that we use write(2) here
+ * and ignore the return value because some kernels have a bug that
+ * returns 0 rather than bytes written on success, sending us into an
+ * infinite retry loop using other write mechanisms.
+ */
+ fd = open(reset_file, O_WRONLY);
+ if (fd != -1) {
+ ret = write(fd, reset, strlen(reset));
+ close(fd);
+ }
/*
* When a 0 is written to the command register, the device is logically
* disconnected from the PCI bus. This avoids further DMA transfers.
*/
- assigned_dev_pci_write_config(d, PCI_COMMAND, 0, 2);
+ assigned_dev_pci_write_config(pci_dev, PCI_COMMAND, 0, 2);
}
static int assigned_initfn(struct PCIDevice *pci_dev)
--
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