On Wed, Oct 07, 2009 at 10:20:19AM +0200, Avi Kivity wrote:
> On 10/05/2009 04:53 PM, Anthony Liguori wrote:
>> From: Michael S. Tsirkin<mst@xxxxxxxxxx>
>>
>> Reset BARs and a couple of other registers on bus reset, as per PCI
>> spec.
>>
>
> This commit breaks Windows XP restart.
I'll look into this.
> After a restart Windows switches
> from 800x600 cirrus logic vga to 640x480 standard vga. My guess is that
> this is due to two mutually-cancelling bugs:
>
> - the bios fails to initialize one of the registers touched below
> - qemu sets up that register in the state the Windows expects the bios
> to leave it in instead of the on-reset state
>
> Once we perform the reset the register reverts to its correct reset
> state, the bios fails to initialize it, and Windows ignores the device.
>
> I reverted this commit from qemu-kvm.git.
>
>> diff --git a/hw/pci.c b/hw/pci.c
>> index 2dd7213..e2f88ff 100644
>> --- a/hw/pci.c
>> +++ b/hw/pci.c
>> @@ -92,7 +92,20 @@ static inline int pci_bar(int reg)
>>
>> static void pci_device_reset(PCIDevice *dev)
>> {
>> + int r;
>> +
>> memset(dev->irq_state, 0, sizeof dev->irq_state);
>> + dev->config[PCI_COMMAND]&= ~(PCI_COMMAND_IO | PCI_COMMAND_MEMORY |
>> + PCI_COMMAND_MASTER);
>> + dev->config[PCI_CACHE_LINE_SIZE] = 0x0;
>> + dev->config[PCI_INTERRUPT_LINE] = 0x0;
>> + for (r = 0; r< PCI_NUM_REGIONS; ++r) {
>> + if (!dev->io_regions[r].size) {
>> + continue;
>> + }
>> + pci_set_long(dev->config + pci_bar(r), dev->io_regions[r].type);
>> + }
>> + pci_update_mappings(dev);
>> }
>>
>> static void pci_bus_reset(void *opaque)
>>
>>
>>
>
>
> --
> Do not meddle in the internals of kernels, for they are subtle and quick to panic.
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