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

[Alex Bennée <alex.bennee@xxxxxxxxxx>]

Julien Grall <julien@xxxxxxx> writes:

> 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).

Ahh at the time I wasn't sure if there was another regression in master
so I was basing of stable. I'll re-base of master next time ;-)

-- 
Alex Bennée