Re: [PATCH V2] arm64/mm: Fix __enable_mmu() for new TGRAN range values

[Zenghui Yu <yuzenghui@huawei.com>]

On 2022/8/26 20:00, Anders Roxell wrote:
> On 2021-03-10 11:23, Anshuman Khandual wrote:
>> From: James Morse <james.morse@arm.com>
>>
>> As per ARM ARM DDI 0487G.a, when FEAT_LPA2 is implemented, ID_AA64MMFR0_EL1
>> might contain a range of values to describe supported translation granules
>> (4K and 16K pages sizes in particular) instead of just enabled or disabled
>> values. This changes __enable_mmu() function to handle complete acceptable
>> range of values (depending on whether the field is signed or unsigned) now
>> represented with ID_AA64MMFR0_TGRAN_SUPPORTED_[MIN..MAX] pair. While here,
>> also fix similar situations in EFI stub and KVM as well.
>>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Marc Zyngier <maz@kernel.org>
>> Cc: James Morse <james.morse@arm.com>
>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Cc: Ard Biesheuvel <ardb@kernel.org>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: kvmarm@lists.cs.columbia.edu
>> Cc: linux-efi@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>> Acked-by: Marc Zyngier <maz@kernel.org>
>> Signed-off-by: James Morse <james.morse@arm.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> 
> Hi,
> 
> When building an arm64 defconfig kernel from stable/linux-5.10.y and
> booting that in QEMU (version: 1:7.0+dfsg-2~bpo11+2) with '-cpu max' the
> kernel doesn't boot. I don't get any output.  The kernel boots fine if I
> change to '-cpu cortex-a72'.
> 
> If I cherry-pick this patch to stable/linux-5.10.y I'm able too boot the
> kernel with '-cpu max'.

You can workaround the kernel boot failure by specifying
'-cpu max,lpa2=off' [*] in the QEMU command line.

> However, I'm not comfortable to backport this patch to older kernels
> since there are a lot of conflicts.
> Can someone help out to do the packport?

Upstream commit 26f55386f964 ("arm64/mm: Fix __enable_mmu() for new
TGRAN range values") can still be applied cleanly on top of
linux-5.10.y. I can send it to <stable@vger.kernel.org> if maintainers
are okay with the stable-5.10 backport.

[*] https://gitlab.com/qemu-project/qemu/-/commit/69b2265d5fe8

Zenghui