linux-kernel - Re: [PATCH v8 9/9] KVM: arm64: Add support for creating PUD hugepages at stage 2

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Message-ID: <87y3bgk9wk.fsf@e105922-lin.cambridge.arm.com>
Date:   Tue, 02 Oct 2018 09:52:43 +0100
From:   Punit Agrawal <punit.agrawal@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     <kvmarm@...ts.cs.columbia.edu>, <marc.zyngier@....com>,
        <will.deacon@....com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Christoffer Dall <christoffer.dall@....com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v8 9/9] KVM: arm64: Add support for creating PUD hugepages at stage 2

Suzuki K Poulose <suzuki.poulose@....com> writes:

> On 10/01/2018 04:54 PM, Punit Agrawal wrote:
>> KVM only supports PMD hugepages at stage 2. Now that the various page
>> handling routines are updated, extend the stage 2 fault handling to
>> map in PUD hugepages.
>>
>> Addition of PUD hugepage support enables additional page sizes (e.g.,
>> 1G with 4K granule) which can be useful on cores that support mapping
>> larger block sizes in the TLB entries.
>>
>> Signed-off-by: Punit Agrawal <punit.agrawal@....com>
>> Cc: Christoffer Dall <christoffer.dall@....com>
>> Cc: Marc Zyngier <marc.zyngier@....com>
>> Cc: Russell King <linux@...linux.org.uk>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will.deacon@....com>
>> ---
>>   arch/arm/include/asm/kvm_mmu.h         |  20 +++++
>>   arch/arm/include/asm/stage2_pgtable.h  |   9 +++
>>   arch/arm64/include/asm/kvm_mmu.h       |  16 ++++
>>   arch/arm64/include/asm/pgtable-hwdef.h |   2 +
>>   arch/arm64/include/asm/pgtable.h       |   2 +
>>   virt/kvm/arm/mmu.c                     | 106 +++++++++++++++++++++++--
>>   6 files changed, 149 insertions(+), 6 deletions(-)
>>
>
> ...
>
>> diff --git a/arch/arm/include/asm/stage2_pgtable.h b/arch/arm/include/asm/stage2_pgtable.h
>> index f6a7ea805232..a4ec25360e50 100644
>> --- a/arch/arm/include/asm/stage2_pgtable.h
>> +++ b/arch/arm/include/asm/stage2_pgtable.h
>> @@ -68,4 +68,13 @@ stage2_pmd_addr_end(struct kvm *kvm, phys_addr_t addr, phys_addr_t end)
>>   #define stage2_pmd_table_empty(kvm, pmdp)	kvm_page_empty(pmdp)
>>   #define stage2_pud_table_empty(kvm, pudp)	false
>>   +static inline bool kvm_stage2_has_pud(struct kvm *kvm)
>> +{
>> +#if CONFIG_PGTABLE_LEVELS > 3
>> +	return true;
>> +#else
>> +	return false;
>> +#endif
>
> nit: We can only have PGTABLE_LEVELS=3 on ARM with LPAE.
> AFAIT, this can be set to false always for ARM.

I debated this and veered towards being generic but not committed either
ways.

I've updated this locally but will wait for further comments before
re-posting.

>
>> +}
>> +
>
> ...
>
>> @@ -1669,7 +1752,18 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>   	needs_exec = exec_fault ||
>>   		(fault_status == FSC_PERM && stage2_is_exec(kvm, fault_ipa));
>>   -	if (hugetlb && vma_pagesize == PMD_SIZE) {
>> +	if (hugetlb && vma_pagesize == PUD_SIZE) {
>> +		pud_t new_pud = kvm_pfn_pud(pfn, mem_type);
>> +
>> +		new_pud = kvm_pud_mkhuge(new_pud);
>> +		if (writable)
>> +			new_pud = kvm_s2pud_mkwrite(new_pud);
>> +
>> +		if (needs_exec)
>> +			new_pud = kvm_s2pud_mkexec(new_pud);
>> +
>> +		ret = stage2_set_pud_huge(kvm, memcache, fault_ipa, &new_pud);
>> +	} else if (hugetlb && vma_pagesize == PMD_SIZE) {
>>   		pmd_t new_pmd = kvm_pfn_pmd(pfn, mem_type);
>>     		new_pmd = kvm_pmd_mkhuge(new_pmd);
>>
>
>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>

Thanks a lot for going through the series.