Re: [Qemu-devel] call flow to hit get_pci_config_device() during live migration

[Chris Friesen]

On 06/09/2017 02:00 PM, Chris Friesen wrote:

> I think what I end up with is that byte 0x20 (ie 32) of the PCI config for the
> virtio-blk device is 0 in the data coming over the wire, and 0xC in the local
> copy.  Since cmask is 0xff we need to check all the bits in the byte, and both
> wmask and w1cmask are 0 so the version on the wire and the local version should
> be the same.

I've confirmed that if I boot with a machine type of pc-i440fx-2.2 on the older 
version of qemu then I get different output in lspci -vv for the virtio-blk device.

One the older version I get:

        Region 0: I/O ports at c000 [size=64]
        Region 1: Memory at febd6000 (32-bit, non-prefetchable) [size=4K]
        Capabilities: [40] MSI-X: Enable+ Count=2 Masked-
                Vector table: BAR=1 offset=00000000
                PBA: BAR=1 offset=00000800


On the new version I get:

        Region 0: I/O ports at c000 [size=64]
        Region 1: Memory at febd2000 (32-bit, non-prefetchable) [size=4K]
        Region 4: Memory at fe004000 (64-bit, prefetchable) [size=16K]
        Capabilities: [98] MSI-X: Enable+ Count=2 Masked-
                Vector table: BAR=1 offset=00000000
                PBA: BAR=1 offset=00000800
        Capabilities: [84] Vendor Specific Information: Len=14 <?>
        Capabilities: [70] Vendor Specific Information: Len=14 <?>
        Capabilities: [60] Vendor Specific Information: Len=10 <?>
        Capabilities: [50] Vendor Specific Information: Len=10 <?>
        Capabilities: [40] Vendor Specific Information: Len=10 <?>

We had to patch the CentOS/RHEL versions of qemu-kvm-ev to enable support for 
the pc-i440fx-2.2 machine type, and it seems we missed something on the newer 
version.

Can someone point me to the code that sets up the PCI config space for the 
virtio-blk device?  I'd like to figure out what's adding Region 4 and the extra 
capabilities.

Chris