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From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, linux-mm@kvack.org,
	Sean Christopherson <seanjc@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	Will Deacon <will@kernel.org>,
	Quentin Perret <qperret@google.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kernel-team@android.com
Subject: Re: [PATCH 1/5] KVM: arm64: Walk userspace page tables to compute the THP mapping size
Date: Mon, 19 Jul 2021 10:31:51 +0100	[thread overview]
Message-ID: <87o8ayk5tk.wl-maz@kernel.org> (raw)
In-Reply-To: <c04fc75d-0f2a-3a3f-f698-eaf5e2aa00bd@redhat.com>

On Mon, 19 Jul 2021 07:31:30 +0100,
Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> On 17/07/21 11:55, Marc Zyngier wrote:
> > We currently rely on the kvm_is_transparent_hugepage() helper to
> > discover whether a given page has the potential to be mapped as
> > a block mapping.
> > 
> > However, this API doesn't really give un everything we want:
> > - we don't get the size: this is not crucial today as we only
> >    support PMD-sized THPs, but we'd like to have larger sizes
> >    in the future
> > - we're the only user left of the API, and there is a will
> >    to remove it altogether
> > 
> > To address the above, implement a simple walker using the existing
> > page table infrastructure, and plumb it into transparent_hugepage_adjust().
> > No new page sizes are supported in the process.
> > 
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> 
> If it's okay for you to reuse the KVM page walker that's fine of
> course, but the arch/x86/mm functions lookup_address_in_{mm,pgd} are
> mostly machine-independent and it may make sense to move them to mm/.
>
> That would also allow reusing the x86 function host_pfn_mapping_level.

That could work to some extent, but the way the x86 code equates level
to mapping size is a bit at odds with the multiple page sizes that
arm64 deals with.

We're also trying to move away from the whole P*D abstraction, because
this isn't something we want to deal with in the self-contained EL2
object.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

WARNING: multiple messages have this Message-ID
From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kernel-team@android.com, kvm@vger.kernel.org,
	Sean Christopherson <seanjc@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	linux-mm@kvack.org, Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/5] KVM: arm64: Walk userspace page tables to compute the THP mapping size
Date: Mon, 19 Jul 2021 10:31:51 +0100	[thread overview]
Message-ID: <87o8ayk5tk.wl-maz@kernel.org> (raw)
In-Reply-To: <c04fc75d-0f2a-3a3f-f698-eaf5e2aa00bd@redhat.com>

On Mon, 19 Jul 2021 07:31:30 +0100,
Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> On 17/07/21 11:55, Marc Zyngier wrote:
> > We currently rely on the kvm_is_transparent_hugepage() helper to
> > discover whether a given page has the potential to be mapped as
> > a block mapping.
> > 
> > However, this API doesn't really give un everything we want:
> > - we don't get the size: this is not crucial today as we only
> >    support PMD-sized THPs, but we'd like to have larger sizes
> >    in the future
> > - we're the only user left of the API, and there is a will
> >    to remove it altogether
> > 
> > To address the above, implement a simple walker using the existing
> > page table infrastructure, and plumb it into transparent_hugepage_adjust().
> > No new page sizes are supported in the process.
> > 
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> 
> If it's okay for you to reuse the KVM page walker that's fine of
> course, but the arch/x86/mm functions lookup_address_in_{mm,pgd} are
> mostly machine-independent and it may make sense to move them to mm/.
>
> That would also allow reusing the x86 function host_pfn_mapping_level.

That could work to some extent, but the way the x86 code equates level
to mapping size is a bit at odds with the multiple page sizes that
arm64 deals with.

We're also trying to move away from the whole P*D abstraction, because
this isn't something we want to deal with in the self-contained EL2
object.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID
From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	kvmarm@lists.cs.columbia.edu, linux-mm@kvack.org,
	Sean Christopherson <seanjc@google.com>,
	Matthew Wilcox <willy@infradead.org>,
	Will Deacon <will@kernel.org>,
	Quentin Perret <qperret@google.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kernel-team@android.com
Subject: Re: [PATCH 1/5] KVM: arm64: Walk userspace page tables to compute the THP mapping size
Date: Mon, 19 Jul 2021 10:31:51 +0100	[thread overview]
Message-ID: <87o8ayk5tk.wl-maz@kernel.org> (raw)
In-Reply-To: <c04fc75d-0f2a-3a3f-f698-eaf5e2aa00bd@redhat.com>

On Mon, 19 Jul 2021 07:31:30 +0100,
Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> On 17/07/21 11:55, Marc Zyngier wrote:
> > We currently rely on the kvm_is_transparent_hugepage() helper to
> > discover whether a given page has the potential to be mapped as
> > a block mapping.
> > 
> > However, this API doesn't really give un everything we want:
> > - we don't get the size: this is not crucial today as we only
> >    support PMD-sized THPs, but we'd like to have larger sizes
> >    in the future
> > - we're the only user left of the API, and there is a will
> >    to remove it altogether
> > 
> > To address the above, implement a simple walker using the existing
> > page table infrastructure, and plumb it into transparent_hugepage_adjust().
> > No new page sizes are supported in the process.
> > 
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> 
> If it's okay for you to reuse the KVM page walker that's fine of
> course, but the arch/x86/mm functions lookup_address_in_{mm,pgd} are
> mostly machine-independent and it may make sense to move them to mm/.
>
> That would also allow reusing the x86 function host_pfn_mapping_level.

That could work to some extent, but the way the x86 code equates level
to mapping size is a bit at odds with the multiple page sizes that
arm64 deals with.

We're also trying to move away from the whole P*D abstraction, because
this isn't something we want to deal with in the self-contained EL2
object.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-07-19  9:32 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-17  9:55 [PATCH 0/5] KVM: Remove kvm_is_transparent_hugepage() and friends Marc Zyngier
2021-07-17  9:55 ` Marc Zyngier
2021-07-17  9:55 ` Marc Zyngier
2021-07-17  9:55 ` [PATCH 1/5] KVM: arm64: Walk userspace page tables to compute the THP mapping size Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-19  6:31   ` Paolo Bonzini
2021-07-19  6:31     ` Paolo Bonzini
2021-07-19  6:31     ` Paolo Bonzini
2021-07-19  9:31     ` Marc Zyngier [this message]
2021-07-19  9:31       ` Marc Zyngier
2021-07-19  9:31       ` Marc Zyngier
2021-07-20 17:23   ` Alexandru Elisei
2021-07-20 17:23     ` Alexandru Elisei
2021-07-20 17:23     ` Alexandru Elisei
2021-07-20 20:33     ` Sean Christopherson
2021-07-20 20:33       ` Sean Christopherson
2021-07-20 20:33       ` Sean Christopherson
2021-07-21 14:58       ` Will Deacon
2021-07-21 14:58         ` Will Deacon
2021-07-21 14:58         ` Will Deacon
2021-07-21 15:56         ` Sean Christopherson
2021-07-21 15:56           ` Sean Christopherson
2021-07-21 15:56           ` Sean Christopherson
2021-07-21 16:37       ` Alexandru Elisei
2021-07-21 16:37         ` Alexandru Elisei
2021-07-21 16:37         ` Alexandru Elisei
2021-07-23  8:48     ` Marc Zyngier
2021-07-23  8:48       ` Marc Zyngier
2021-07-23  8:48       ` Marc Zyngier
2021-07-17  9:55 ` [PATCH 2/5] KVM: arm64: Avoid mapping size adjustment on permission fault Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-23 15:55   ` Alexandru Elisei
2021-07-23 15:55     ` Alexandru Elisei
2021-07-23 15:55     ` Alexandru Elisei
2021-07-23 16:18     ` Marc Zyngier
2021-07-23 16:18       ` Marc Zyngier
2021-07-23 16:18       ` Marc Zyngier
2021-07-17  9:55 ` [PATCH 3/5] KVM: Remove kvm_is_transparent_hugepage() and PageTransCompoundMap() Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-19  6:31   ` Paolo Bonzini
2021-07-19  6:31     ` Paolo Bonzini
2021-07-19  6:31     ` Paolo Bonzini
2021-07-17  9:55 ` [PATCH 4/5] KVM: arm64: Use get_page() instead of kvm_get_pfn() Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-17  9:55 ` [PATCH 5/5] KVM: Get rid " Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-17  9:55   ` Marc Zyngier
2021-07-19  6:31   ` Paolo Bonzini
2021-07-19  6:31     ` Paolo Bonzini
2021-07-19  6:31     ` Paolo Bonzini

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