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

[Stefan Weil]

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?

And the check for unaligned writes is, well, unusual :-)

Regards,
Stefan