linux-kernel - Re: [PATCH v2 08/17] kvm: arm/arm64: Prepare for VM specific stage2 translations

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Date:   Fri, 27 Apr 2018 17:04:42 +0100
From:   Julien Grall <julien.grall@....com>
To:     Suzuki K Poulose <Suzuki.Poulose@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     ard.biesheuvel@...aro.org, kvm@...r.kernel.org,
        marc.zyngier@....com, catalin.marinas@....com,
        punit.agrawal@....com, will.deacon@....com,
        linux-kernel@...r.kernel.org, kristina.martsenko@....com,
        pbonzini@...hat.com, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH v2 08/17] kvm: arm/arm64: Prepare for VM specific stage2
 translations

Hi Suzuki,

On 27/04/18 16:58, Suzuki K Poulose wrote:
> On 27/04/18 16:22, Suzuki K Poulose wrote:
>> On 26/04/18 14:35, Julien Grall wrote:
>>> Hi Suzuki,
>>>
>>> On 27/03/18 14:15, Suzuki K Poulose wrote:
>>>> Right now the stage2 page table for a VM is hard coded, assuming
>>>> an IPA of 40bits. As we are about to add support for per VM IPA,
>>>> prepare the stage2 page table helpers to accept the kvm instance
>>>> to make the right decision for the VM. No functional changes.
>>
>>
>>>> diff --git a/arch/arm/include/asm/kvm_arm.h 
>>>> b/arch/arm/include/asm/kvm_arm.h
>>>> index 3ab8b37..c3f1f9b 100644
>>>> --- a/arch/arm/include/asm/kvm_arm.h
>>>> +++ b/arch/arm/include/asm/kvm_arm.h
>>>> @@ -133,8 +133,7 @@
>>>>    * space.
>>>>    */
>>>>   #define KVM_PHYS_SHIFT    (40)
>>>> -#define KVM_PHYS_SIZE    (_AC(1, ULL) << KVM_PHYS_SHIFT)
>>>> -#define KVM_PHYS_MASK    (KVM_PHYS_SIZE - _AC(1, ULL))
>>>
>>> I assume you are moving them to kvm_mmu.h in order to match the arm64 
>>> side, right? If so, would not it make sense to make KVM_PHYS_SHIFT 
>>> with it?
>>>
>>> [...]
>>
>> I am moving all the macros that depend on the "kvm" instance to 
>> kvm_mmu.h.
>> I will see if I can move the KVM_PHYS_SHIFT without much trouble.
> 
> It looks like we can't do that easily. KVM_PHYS_SHIFT is used for KVM_T0SZ
> on arm, even though that can be simply hard coded to avoid the 
> dependency on
> KVM_PHYS_SHIFT (like we did for arm64, T0SZ is defined to 24). I would 
> leave it
> as it is to avoid the noise.

Fine. That was only a suggestion :).

Cheers,

-- 
Julien Grall