linux-kernel - Re: [PATCH v3 07/20] kvm: arm/arm64: Prepare for VM specific stage2 translations

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Date:   Mon, 2 Jul 2018 11:59:49 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Auger Eric <eric.auger@...hat.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, james.morse@....com,
        marc.zyngier@....com, cdall@...nel.org, julien.grall@....com,
        will.deacon@....com, catalin.marinas@....com,
        punit.agrawal@....com, qemu-devel@...gnu.org
Subject: Re: [PATCH v3 07/20] kvm: arm/arm64: Prepare for VM specific stage2
 translations


Hi Eric,

On 02/07/18 11:51, Auger Eric wrote:
> Hi Suzuki,
> 
> On 06/29/2018 01:15 PM, 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.
>> Adds stage2_pgd_size(kvm) to replace S2_PGD_SIZE. Also, moves
>> some of the definitions dependent on kvm instance to asm/kvm_mmu.h
>> for arm32. In that process drop the _AC() specifier constants
>>
>> Cc: Marc Zyngier <marc.zyngier@....com>
>> Cc: Christoffer Dall <cdall@...nel.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> ---
>> Changes since V2:
>>   - Update commit description abuot the movement to asm/kvm_mmu.h
>>     for arm32
>>   - Drop _AC() specifiers


>> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
>> index 8553d68..f36eb20 100644
>> --- a/arch/arm/include/asm/kvm_mmu.h
>> +++ b/arch/arm/include/asm/kvm_mmu.h
>> @@ -36,15 +36,19 @@
>>   	})
>>   
>>   /*
>> - * KVM_MMU_CACHE_MIN_PAGES is the number of stage2 page table translation levels.
>> + * kvm_mmu_cache_min_pages() is the number of stage2 page
>> + * table translation levels, excluding the top level, for
>> + * the given VM. Since we have a 3 level page-table, this
>> + * is fixed.
>>    */
>> -#define KVM_MMU_CACHE_MIN_PAGES	2
>> +#define kvm_mmu_cache_min_pages(kvm)	2
> nit: In addition to Marc'c comment, I can see it defined in
> stage2_pgtable.h on arm64 side. Can't we align?

Sure, will do that.

>> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
>> index fb9a712..5da8f52 100644
>> --- a/arch/arm64/include/asm/kvm_mmu.h
>> +++ b/arch/arm64/include/asm/kvm_mmu.h
>> @@ -141,8 +141,11 @@ 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))
> Can't you get rid of _AC() also in arm64 case?
> 

>> +#define kvm_phys_mask(kvm)		(kvm_phys_size(kvm) - _AC(1, ULL))

Yes, that missed. I will do it. Thanks for spotting.

Cheers
Suzuki