From: Peter Maydell <peter.maydell@linaro.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>, qemu-arm <qemu-arm@nongnu.org>,
"open list:RISC-V" <qemu-riscv@nongnu.org>,
QEMU Developers <qemu-devel@nongnu.org>,
Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH v2 for-6.0?] hw/pci-host/gpex: Don't fault for unmapped parts of MMIO and PIO windows
Date: Tue, 20 Apr 2021 13:39:12 +0100 [thread overview]
Message-ID: <CAFEAcA8Cye=jxLX+wKFimov8bo=F_6VF=tFbjskDo3Qe=6O8+Q@mail.gmail.com> (raw)
In-Reply-To: <20210420062357-mutt-send-email-mst@kernel.org>
On Tue, 20 Apr 2021 at 11:24, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Thu, Mar 25, 2021 at 04:33:15PM +0000, Peter Maydell wrote:
> > Currently the gpex PCI controller implements no special behaviour for
> > guest accesses to areas of the PIO and MMIO where it has not mapped
> > any PCI devices, which means that for Arm you end up with a CPU
> > exception due to a data abort.
> >
> > Most host OSes expect "like an x86 PC" behaviour, where bad accesses
> > like this return -1 for reads and ignore writes. In the interests of
> > not being surprising, make host CPU accesses to these windows behave
> > as -1/discard where there's no mapped PCI device.
> >
> > The old behaviour generally didn't cause any problems, because
> > almost always the guest OS will map the PCI devices and then only
> > access where it has mapped them. One corner case where you will see
> > this kind of access is if Linux attempts to probe legacy ISA
> > devices via a PIO window access. So far the only case where we've
> > seen this has been via the syzkaller fuzzer.
> >
> > Reported-by: Dmitry Vyukov <dvyukov@google.com>
> > Fixes: https://bugs.launchpad.net/qemu/+bug/1918917
> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>
>
> Looks ok superficially
>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
>
> Peter pls merge if appropriate.
Thanks; I'll take it via target-arm.next for 6.1 (it'll need
a tweak to use hw_compat_6_0 rather than hw_compat_5_2 so it might
need to wait until the patch adding hw_compat_6_0 hits master.)
-- PMM
prev parent reply other threads:[~2021-04-20 12:47 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 16:33 [PATCH v2 for-6.0?] hw/pci-host/gpex: Don't fault for unmapped parts of MMIO and PIO windows Peter Maydell
2021-03-25 17:01 ` Richard Henderson
2021-03-25 17:03 ` Michael S. Tsirkin
2021-03-25 18:14 ` Philippe Mathieu-Daudé
2021-04-19 13:42 ` Peter Maydell
2021-04-20 11:52 ` Philippe Mathieu-Daudé
2021-04-20 12:26 ` Arnd Bergmann
2021-04-20 12:31 ` Philippe Mathieu-Daudé
2021-04-20 10:24 ` Michael S. Tsirkin
2021-04-20 12:39 ` Peter Maydell [this message]
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