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From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	Quentin Perret <qperret@google.com>,
	Will Deacon <will@kernel.org>, Reiji Watanabe <reijiw@google.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH 3/5] KVM: arm64: Only return attributes from stage2_update_leaf_attrs()
Date: Thu, 2 Feb 2023 22:08:37 +0000	[thread overview]
Message-ID: <Y9w0ZYVXRgpTKuFD@google.com> (raw)
In-Reply-To: <Y77wCeSYo7POSs3z@google.com>

On Wed, Jan 11, 2023 at 05:21:13PM +0000, Oliver Upton wrote:
> Hey Marc,
> 
> On Wed, Jan 11, 2023 at 08:52:25AM +0000, Marc Zyngier wrote:
> > [+ Suzuki and Zenghui who are missing from the Cc list]
> 
> Doh! Just switched over to working out of a new git tree and didn't move
> over my cc-cmd. Apologies to you two.
> 
> > On Wed, 11 Jan 2023 00:02:58 +0000,
> > Oliver Upton <oliver.upton@linux.dev> wrote:
> > > 
> > > Returning a single PTE from stage2_update_leaf_attrs() doesn't make a
> > > great deal of sense given that the function could be used to apply a
> > > change to a range of PTEs. Instead, return a bitwise OR of attributes
> > > from all the visited PTEs.
> > 
> > I find this amalgamation of attributes quite confusing, and I have a
> > hard time attaching semantics to the resulting collection of bits.
> > 
> > It also means that you cannot reason about a particular attribute
> > being 0 if any of the neighbour PTEs has this bit set.
> 
> Very true. What I had really wanted to do was make a walker that allows
> software to check the state of specific attribute bit(s) within a range
> of memory instead of returning all of them. I decided against it because
> it would put more churn on other callers or require a new walker
> entirely.
> 
> Anyway, I can go about that change to make this a bit easier to reason
> about. Thoughts?

LOL, I thought I hadn't replied which is why I didn't hear anything
back. Ball is in your court, Marc, any thoughts?

--
Thanks,
Oliver

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  reply	other threads:[~2023-02-02 22:09 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-11  0:02 [PATCH 0/5] KVM: arm64: Handle unaligned memslots in kvm_(test_)_age_gfn() Oliver Upton
2023-01-11  0:02 ` [PATCH 1/5] KVM: arm64: Hoist S2 PTE definitions into kvm_pgtable.h Oliver Upton
2023-01-11  0:02 ` [PATCH 2/5] KVM: arm64: Add a mask for all leaf PTE attributes Oliver Upton
2023-01-11  0:02 ` [PATCH 3/5] KVM: arm64: Only return attributes from stage2_update_leaf_attrs() Oliver Upton
2023-01-11  8:52   ` Marc Zyngier
2023-01-11 17:21     ` Oliver Upton
2023-02-02 22:08       ` Oliver Upton [this message]
2023-02-07 14:56         ` Marc Zyngier
2023-01-11  0:02 ` [PATCH 4/5] KVM: arm64: Correctly handle page aging notifiers for unaligned memlsot Oliver Upton
2023-01-12 15:44   ` Marc Zyngier
2023-01-11  0:03 ` [PATCH 5/5] KVM: arm64: Consistently use KVM's types/helpers in kvm_age_gfn() Oliver Upton

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