On Sun, 26 May 2019 at 14:58, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
>
> On Sun, 26 May 2019 at 12:45, Antti Seppälä <a.seppala@xxxxxxxxx> wrote:
> >
> > On Sun, 26 May 2019 at 13:11, Stefan Wahren <wahrenst@xxxxxxx> wrote:
> > >
> > > Hi,
> > >
> > > i want to remind about an issue which was originally reported by Wayne
> > > Piekarski [1]. I'm able to reproduce this oops with Mainline Linux 5.0.2
> > > on a Raspberry Pi 3B+ (arm64/defconfig) and according to Jan Kratochvil
> > > [2] this applies to 5.1.0 and 5.2.0.
> > >
> > > The crash is reproducible since commit c55191e96ca ("arm64: mm: apply
> > > r/o permissions of VM areas to its linear alias as well"), but the root
> > > cause of the crash was introduced much earlier with commit 56406e017a88
> > > ("usb: dwc2: Fix DMA alignment to start at allocated boundary").
> > >
> > > I tested successfully the following workarounds with the RPi 3B+:
> > >
> > > 1) Disable RODATA_FULL_DEFAULT_ENABLED
> > >
> > > 2) revert commit 56406e017a88 ("usb: dwc2: Fix DMA alignment to start at
> > > allocated boundary")
> > >
> > > It would be nice if someone can come up with a proper solution.
> > >
> > > Regards
> > > Stefan
> > >
> > > [1] - https://marc.info/?l=linux-usb&m=155440243702650&w=2
> > > [2] - https://bugzilla.kernel.org/show_bug.cgi?id=203149
> > >
> >
> > Hello.
> >
> > This is just a shot in the dark but have you tried to apply DMA cache
> > alignment issue fix [1] as a third workaround alternative?
> > If it helps the fix should be merged upstream.
> >
>
Apologies, I should have looked at the patch first :-)
It does exactly what I proposed - ensure that DMA related cache
invalidation does not wipe the stored_xfer_buffer pointer.
sorry for the noise
