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From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Marc Zyngier <maz@kernel.org>,
	linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, linux-mm@kvack.org
Cc: Sean Christopherson <seanjc@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Will Deacon <will@kernel.org>,
	Quentin Perret <qperret@google.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	kernel-team@android.com
Subject: Re: [PATCH v2 3/6] KVM: arm64: Avoid mapping size adjustment on permission fault
Date: Tue, 27 Jul 2021 17:00:37 +0100	[thread overview]
Message-ID: <5216fbb0-1df2-325c-5e4d-98245c7470e6@arm.com> (raw)
In-Reply-To: <20210726153552.1535838-4-maz@kernel.org>

Hi Marc,

On 7/26/21 4:35 PM, Marc Zyngier wrote:
> Since we only support PMD-sized mappings for THP, getting
> a permission fault on a level that results in a mapping
> being larger than PAGE_SIZE is a sure indication that we have
> already upgraded our mapping to a PMD.
>
> In this case, there is no need to try and parse userspace page
> tables, as the fault information already tells us everything.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  arch/arm64/kvm/mmu.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 0adc1617c557..ebb28dd4f2c9 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1076,9 +1076,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	 * If we are not forced to use page mapping, check if we are
>  	 * backed by a THP and thus use block mapping if possible.
>  	 */
> -	if (vma_pagesize == PAGE_SIZE && !(force_pte || device))
> -		vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva,
> -							   &pfn, &fault_ipa);
> +	if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) {
> +		if (fault_status == FSC_PERM && fault_granule > PAGE_SIZE)
> +			vma_pagesize = fault_granule;
> +		else
> +			vma_pagesize = transparent_hugepage_adjust(kvm, memslot,
> +								   hva, &pfn,
> +								   &fault_ipa);
> +	}

Looks good:

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>

Thanks,

Alex

>  
>  	if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
>  		/* Check the VMM hasn't introduced a new VM_SHARED VMA */


  reply	other threads:[~2021-07-27 15:59 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-26 15:35 [PATCH v2 0/6] KVM: Remove kvm_is_transparent_hugepage() and friends Marc Zyngier
2021-07-26 15:35 ` [PATCH v2 1/6] KVM: arm64: Introduce helper to retrieve a PTE and its level Marc Zyngier
2021-07-27 10:29   ` Quentin Perret
2021-07-27 15:25   ` Alexandru Elisei
2021-07-28 12:17     ` Marc Zyngier
2021-07-26 15:35 ` [PATCH v2 2/6] KVM: arm64: Walk userspace page tables to compute the THP mapping size Marc Zyngier
2021-07-27 15:55   ` Alexandru Elisei
2021-07-26 15:35 ` [PATCH v2 3/6] KVM: arm64: Avoid mapping size adjustment on permission fault Marc Zyngier
2021-07-27 16:00   ` Alexandru Elisei [this message]
2021-07-26 15:35 ` [PATCH v2 4/6] KVM: Remove kvm_is_transparent_hugepage() and PageTransCompoundMap() Marc Zyngier
2021-07-26 15:35 ` [PATCH v2 5/6] KVM: arm64: Use get_page() instead of kvm_get_pfn() Marc Zyngier
2021-07-27 17:46   ` Alexandru Elisei
2021-07-26 15:35 ` [PATCH v2 6/6] KVM: Get rid " Marc Zyngier
2021-08-02 13:39 ` [PATCH v2 0/6] KVM: Remove kvm_is_transparent_hugepage() and friends Marc Zyngier

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