Re: [Qemu-devel] [RFC/PATCH] Fix guest OS panic when 64bit BAR is present

[Michael S. Tsirkin]

On Wed, Jan 25, 2012 at 06:46:03PM +1300, Alexey Korolev wrote:
> Hi, 
> In this post
> http://lists.gnu.org/archive/html/qemu-devel/2011-12/msg03171.html I've
> mentioned about the issues when 64Bit PCI BAR is present and 32bit
> address range is selected for it.
> The issue affects all recent qemu releases and all
> old and recent guest Linux kernel versions.
> 

For testing, I applied the following patch to qemu,
converting msix bar to 64 bit.
Guest did not seem to crash.
I booted Fedora Live CD 32 bit guest on a 32 bit host
to level 3 without crash, and verified that
the BAR is a 64 bit one, and that I got assigned an address
at fe000000.
command line I used:
qemu-system-x86_64 -bios /scm/seabios/out/bios.bin -snapshot -drive
file=qemu-images/f15-test.qcow2,if=none,id=diskid,cache=unsafe
-device virtio-blk-pci,drive=diskid -net user -net nic,model=ne2k_pci
-cdrom Fedora-15-i686-Live-LXDE.iso

At boot prompt type tab and add '3' to kernel command line
to have guest boot into a fast text console instead
of a graphical one which is very slow.

diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 2ac87ea..5271394 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -711,7 +711,8 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice 
*vdev)
     memory_region_init(&proxy->msix_bar, "virtio-msix", 4096);
     if (vdev->nvectors && !msix_init(&proxy->pci_dev, vdev->nvectors,
                                      &proxy->msix_bar, 1, 0)) {
-        pci_register_bar(&proxy->pci_dev, 1, PCI_BASE_ADDRESS_SPACE_MEMORY,
+        pci_register_bar(&proxy->pci_dev, 1, PCI_BASE_ADDRESS_SPACE_MEMORY |
+                        PCI_BASE_ADDRESS_MEM_TYPE_64,
                          &proxy->msix_bar);
     } else
         vdev->nvectors = 0;