Re: [PATCH v2] xen/arm: p2m don't fall over on FEAT_LPA enabled hw

[Julien Grall <julien@xxxxxxx>]

Hi Alex,

On 10/05/2022 15:47, Alex Bennée wrote:
> Julien Grall <julien@xxxxxxx> writes:
> > On 10/05/2022 15:03, Alex Bennée wrote:
> > > Julien Grall <julien@xxxxxxx> writes:
> > >
> > > > Hi Alex,
> > > >
> > > > On 28/04/2022 11:34, Alex Bennée wrote:
> > > > > When we introduced FEAT_LPA to QEMU's -cpu max we discovered older
> > > > > kernels had a bug where the physical address was copied directly from
> > > > > ID_AA64MMFR0_EL1.PARange field. The early cpu_init code of Xen commits
> > > > > the same error by blindly copying across the max supported range.
> > > > > Unsurprisingly when the page tables aren't set up for these greater
> > > > > ranges hilarity ensues and the hypervisor crashes fairly early on in
> > > > > the boot-up sequence. This happens when we write to the control
> > > > > register in enable_mmu().
> > > > > Attempt to fix this the same way as the Linux kernel does by gating
> > > > > PARange to the maximum the hypervisor can handle. I also had to fix up
> > > > > code in p2m which panics when it sees an "invalid" entry in PARange.
> > > > > Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx>
> > > > > Cc: Richard Henderson <richard.henderson@xxxxxxxxxx>
> > > > > Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > > > > Cc: Julien Grall <julien@xxxxxxx>
> > > > > Cc: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> > > > > Cc: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> > > > Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
> > > Will you pick this up via your tree or do I need to do something
> > > else to
> > > get it upstreamed? I guess it needs to go on master and last stable?
> > We only have one tree in Xen where committers (such as Stefano and I)
> > will commit patches regularly to staging. Osstest will then push to
> > master once the testing passed.
> >
> > I have done that now. Interestingly, git am wasn't able to apply this
> > patch. I had to do with:
> >
> > 42sh> git am --show-current-patch=diff | patch -p1
> > patching file xen/arch/arm/arm64/head.S
> > Hunk #1 succeeded at 474 (offset 1 line).
> > patching file xen/arch/arm/p2m.c
> > Hunk #1 succeeded at 32 with fuzz 2.
> > Hunk #2 succeeded at 2023 (offset -7 lines).
> > Hunk #3 succeeded at 2031 (offset -7 lines).
> > Hunk #4 succeeded at 2062 (offset -7 lines).
> >
> > Which branch did you use for sending the patch?
> 0941d6cb23 from RELEASE-4.16.0
This would explain why. Patch sent to xen-devel should be based on 
staging (or master).
Cheers,

--
Julien Grall