linux-kernel - Re: [PATCH] kvm: arm: Fix handling of stage2 huge mappings

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Message-ID: <c27d5828-3924-e209-82b6-c9168007867b@arm.com>
Date:   Wed, 20 Mar 2019 11:12:47 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     marc.zyngier@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        will.deacon@....com, catalin.marinas@....com, james.morse@....com,
        julien.thierry@....com, wanghaibin.wang@...wei.com,
        lious.lilei@...ilicon.com, lishuo1@...ilicon.com,
        zhengxiang9@...wei.com, yuzenghui@...wei.com,
        christoffer.dall@....com
Subject: Re: [PATCH] kvm: arm: Fix handling of stage2 huge mappings

Marc,

On 20/03/2019 10:35, Marc Zyngier wrote:
> On Wed, 20 Mar 2019 10:23:39 +0000
> Suzuki K Poulose <suzuki.poulose@....com> wrote:
> 
> Hi Suzuki,
> 
>> Marc,
>>
>> On 20/03/2019 10:11, Marc Zyngier wrote:
>>> On Wed, 20 Mar 2019 09:44:38 +0000
>>> Suzuki K Poulose <suzuki.poulose@....com> wrote:
>>>    
>>>> Hi Marc,
>>>>
>>>> On 20/03/2019 08:15, Marc Zyngier wrote:
>>>>> Hi Suzuki,
>>>>>
>>>>> On Tue, 19 Mar 2019 14:11:08 +0000,
>>>>> Suzuki K Poulose <suzuki.poulose@....com> wrote:

...

>>>>>> +		if (!pmd_thp_or_huge(old_pmd)) {
>>>>>> +			unmap_stage2_range(kvm, addr & S2_PMD_MASK, S2_PMD_SIZE);
>>>>>> +			goto retry;
>>>>>   
>>
>>>>>> +		if (!stage2_pud_huge(kvm, old_pud)) {
>>>>>> +			unmap_stage2_range(kvm, addr & S2_PUD_MASK, S2_PUD_SIZE);
>>>>>   
>>
>>>> We should really get rid of the S2_P{U/M}D_* definitions, as they are
>>>> always the same as the host. The only thing that changes is the PGD size
>>>> which varies according to the IPA and the concatenation.
>>>>   
>>
>> Also what do you think about using  P{M,U}D_* instead of S2_P{M,U}D_*
>> above ? I could make that change with the respin.
> 
> Given that this is a fix, I'd like it to be as small as obvious as
> possible, making it easier to backport.
> 
> I'm happy to take another patch for 5.2 that will drop the whole S2_P*
> if we still think that this should be the case (though what I'd really
> like is to have architectural levels instead of these arbitrary
> definitions).

I only meant the two new instances added above in the patch. Of course, I
could send something to fix the existing ones.

Cheers
Suzuki