linux-kernel - Re: [PATCH v5 17/18] kvm: arm64: Limit the minimum number of page table levels

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Date:   Tue, 25 Sep 2018 11:25:35 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Auger Eric <eric.auger@...hat.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        marc.zyngier@....com, cdall@...nel.org, pbonzini@...hat.com,
        rkrcmar@...hat.com, will.deacon@....com, catalin.marinas@....com,
        james.morse@....com, dave.martin@....com, julien.grall@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 17/18] kvm: arm64: Limit the minimum number of page
 table levels

On 09/25/2018 11:00 AM, Auger Eric wrote:
> Hi Suzuki,
> 
> On 9/17/18 12:41 PM, Suzuki K Poulose wrote:
>> Since we are about to remove the lower limit on the IPA size,
>> make sure that we do not go to 1 level page table (e.g, with
>> 32bit IPA on 64K host with concatenation) to avoid splitting
>> the host PMD huge pages at stage2.
>>
>> Cc: Marc Zyngier <marc.zyngier@....com>
>> Cc: Christoffer Dall <cdall@...nel.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> ---
>>   arch/arm64/include/asm/stage2_pgtable.h |  8 +++++++-
>>   arch/arm64/kvm/reset.c                  | 12 +++++++++++-
>>   2 files changed, 18 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/stage2_pgtable.h b/arch/arm64/include/asm/stage2_pgtable.h
>> index 352ec4158fdf..6a56fdff0823 100644
>> --- a/arch/arm64/include/asm/stage2_pgtable.h
>> +++ b/arch/arm64/include/asm/stage2_pgtable.h
>> @@ -72,8 +72,14 @@
>>   /*
>>    * The number of PTRS across all concatenated stage2 tables given by the
>>    * number of bits resolved at the initial level.
>> + * If we force more number of levels than necessary, we may have
> more levels?


>> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
>> index 76972b19bdd7..0393bb974b23 100644
>> --- a/arch/arm64/kvm/reset.c
>> +++ b/arch/arm64/kvm/reset.c

>> @@ -210,7 +219,8 @@ int kvm_arm_config_vm(struct kvm *kvm, unsigned long type)
>>   	vtcr |= (kvm_get_vmid_bits() == 16) ?
>>   		VTCR_EL2_VS_16BIT :
>>   		VTCR_EL2_VS_8BIT;
>> -	vtcr |= VTCR_EL2_LVLS_TO_SL0(stage2_pgtable_levels(KVM_PHYS_SHIFT));
>> +
> nit: new line not requested
> 

Fixed all the above

Suzuki