linux-kernel - Re: [PATCH 3/8] arm64: cpufeature: Add CPU capability for AArch32 EL1 support

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Date:   Wed, 15 Apr 2020 14:15:51 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     will@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, mark.rutland@....com, maz@...nel.org,
        anshuman.khandual@....com, catalin.marinas@....com,
        saiprakash.ranjan@...eaurora.org, dianders@...omium.org,
        kernel-team@...roid.com
Subject: Re: [PATCH 3/8] arm64: cpufeature: Add CPU capability for AArch32 EL1
 support

On 04/15/2020 11:14 AM, Will Deacon wrote:
> On Wed, Apr 15, 2020 at 11:13:54AM +0100, Suzuki K Poulose wrote:
>> On 04/14/2020 10:31 PM, Will Deacon wrote:
>>> Although we emit a "SANITY CHECK" warning and taint the kernel if we
>>> detect a CPU mismatch for AArch32 support at EL1, we still online the
>>> CPU with disastrous consequences for any running 32-bit VMs.
>>>
>>> Introduce a capability for AArch32 support at EL1 so that late onlining
>>> of incompatible CPUs is forbidden.
>>>
>>> Signed-off-by: Will Deacon <will@...nel.org>
>>
>> One of the other important missing sanity check for KVM is the VMID width
>> check. I will code something up.
> 
> Cheers! Do we handle things like the IPA size already?

Good point. No, we don't. I will include this too.

Cheers
Suzuki