[SeaBIOS] [Qemu-devel] Hang when using 9p mounts after last Seabios update

Kevin O'Connor kevin at koconnor.net
Sat Oct 1 18:50:43 CEST 2011

On Thu, Sep 22, 2011 at 12:45:11PM +0100, Daniel P. Berrange wrote:
> On 0.14, 0.15 releaes, this all works just fine. On current GIT master,
> the guest OS will hang during boot.
> To reproduce this you will need my custom initrd for mounting 9p filesystems
> as the root FS. You can get that here:
>   http://berrange.com/~dan/qemu-serial-hang-demo.tar.gz

Thanks for the detailed report.

I've confirmed the issue and tracked it down.  The current SeaBIOS
code gets confused during alignment checking if there are no prefmem
regions found.

The patch below should fix the issue.

Richard, can you also check to see if this seabios patch fixes your


Author: Kevin O'Connor <kevin at koconnor.net>
Date:   Sat Oct 1 12:35:32 2011 -0400

    Fix alignment bug in pci_bios_init_root_regions().
    If there are no memory allocations for a given type then the "max" bar
    size is zero.  However, ALIGN_DOWN does not handle an alignment of
    zero properly.  Catch and handle the zero case.
    Signed-off-by: Kevin O'Connor <kevin at koconnor.net>

diff --git a/src/pciinit.c b/src/pciinit.c
index a857da0..0d8758e 100644
--- a/src/pciinit.c
+++ b/src/pciinit.c
@@ -536,7 +536,7 @@ static void pci_bios_init_bus_bases(struct pci_bus *bus)
-#define ROOT_BASE(top, sum, align) ALIGN_DOWN((top)-(sum),(align))
+#define ROOT_BASE(top, sum, max) ALIGN_DOWN((top)-(sum),(max) ?: 1)
 static int pci_bios_init_root_regions(u32 start, u32 end)

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