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

[Julien Grall <julien@xxxxxxx>]

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>

Cheers,

--
Julien Grall