Re: [Qemu-devel] [PATCH master/stable-1.0] pci: fix corrupted pci conf index register by unaligned write

[Avi Kivity]

On 01/08/2012 11:17 AM, Michael S. Tsirkin wrote:
> On Thu, Jan 05, 2012 at 04:14:29PM +0100, Stefan Weil wrote:
> > Am 04.01.2012 15:47, schrieb Michael S. Tsirkin:
> > >On Wed, Jan 04, 2012 at 04:28:42PM +0200, Avi Kivity wrote:
> > >>Commit d0ed8076cbdc261 converted the PCI config access to the memory
> > >>API, but also inadvertantly changed it to accept unaligned writes,
> > >>and corrupt the index register in the process. This causes a regression
> > >>booting NetBSD.
> > >>
> > >>Fix by ignoring unaligned or non-dword writes.
> > >>
> > >>https://bugs.launchpad.net/qemu/+bug/897771
> > >>
> > >>Reported-by: Andreas Gustafsson <address@hidden>
> > >>Signed-off-by: Avi Kivity <address@hidden>
> > >
> > >Acked-by: Michael S. Tsirkin <address@hidden>
> > >
> > >>---
> > >>
> > >>hw/pci_host.c | 3 +++
> > >>1 files changed, 3 insertions(+), 0 deletions(-)
> > >>
> > >>diff --git a/hw/pci_host.c b/hw/pci_host.c
> > >>index 44c6c20..8041778 100644
> > >>--- a/hw/pci_host.c
> > >>+++ b/hw/pci_host.c
> > >>@@ -101,6 +101,9 @@ static void pci_host_config_write(void
> > >>*opaque, target_phys_addr_t addr,
> > >>
> > >>PCI_DPRINTF("%s addr " TARGET_FMT_plx " len %d val %"PRIx64"\n",
> > >>__func__, addr, len, val);
> > >>+ if (addr != 0 || len != 4) {
> > >>+ return;
> > >>+ }
> > >>s->config_reg = val;
> > >>}
> > >>
> > >>-- 
> > >>1.7.7.1
> > 
> > Non dword writes are quite common. I get them with Linux kernels, too.
> > Do you really want to ignore them?
>
> Are you sure?
> Note this is an io write at cf8. Not an unaligned config write.
>
> > And the check for unaligned writes is, well, unusual :-)

What's unusual?


> This seems to be how memory API behaves ... right, Avi?
> Maybe this should be documented somewhere.

Document what?

-- 
error compiling committee.c: too many arguments to function