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 16:22:12 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Julien Grall <julien.grall@....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

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.

> 
>> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
>> index 7faed6e..594c4e6 100644
>> --- a/arch/arm64/include/asm/kvm_mmu.h
>> +++ b/arch/arm64/include/asm/kvm_mmu.h
>> @@ -134,8 +134,11 @@ static inline unsigned long __kern_hyp_va(unsigned long v)
>>    * We currently only support a 40bit IPA.
>>    */
>>   #define KVM_PHYS_SHIFT    (40)
>> -#define KVM_PHYS_SIZE    (1UL << KVM_PHYS_SHIFT)
>> -#define KVM_PHYS_MASK    (KVM_PHYS_SIZE - 1UL)
>> +
>> +#define kvm_phys_shift(kvm)        KVM_PHYS_SHIFT
>> +#define kvm_phys_size(kvm)        (_AC(1, ULL) << kvm_phys_shift(kvm))
> 
> NIT: is the _AC(...) necessary? It does not look like this function is going to be usable in assembly.
> 
>> +#define kvm_phys_mask(kvm)        (kvm_phys_size(kvm) - _AC(1, ULL))
> 
> Same here.
> 

Ok, will drop them.

Cheers
Suzuki