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From: Oliver Upton <oliver.upton@linux.dev>
To: Will Deacon <will@kernel.org>
Cc: kvm@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	linux-kernel@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/1] KVM: arm64: Use a separate function for hyp stage-1 walks
Date: Tue, 15 Nov 2022 17:23:51 +0000	[thread overview]
Message-ID: <Y3PLJxnvmZp35MpF@google.com> (raw)
In-Reply-To: <20221115132532.GA524@willie-the-truck>

Hey Will,

On Tue, Nov 15, 2022 at 01:25:34PM +0000, Will Deacon wrote:

[...]

> On Mon, Nov 14, 2022 at 08:11:27PM +0000, Oliver Upton wrote:
> > +int kvm_pgtable_hyp_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
> > +			 struct kvm_pgtable_walker *walker);
> 
> Hmm, this feels like slightly the wrong abstraction to me -- there's nothing
> hyp-specific about the problem being solved, it's just that the only user
> is for hyp walks.
> 
> Could we instead rework 'struct kvm_pgtable' slightly so that the existing
> 'flags' field is no-longer stage-2 specific and includes a KVM_PGTABLE_LOCKED
> flag which could be set by kvm_pgtable_hyp_init()?
> 
> That way the top-level API remains unchanged and the existing callers will
> continue to work.

Thanks for the suggestion! Yeah, this should be described by the flags
instead.

We already have KVM_PGTABLE_WALK_SHARED, I could actually condition the
RCU lock/unlock on that one. That would make it an explicit opt-in
instead of requiring an opt out with callers passing KVM_PGTABLE_LOCKED.

Thoughts?

--
Thanks,
Oliver
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

WARNING: multiple messages have this Message-ID (diff)
From: Oliver Upton <oliver.upton@linux.dev>
To: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] KVM: arm64: Use a separate function for hyp stage-1 walks
Date: Tue, 15 Nov 2022 17:23:51 +0000	[thread overview]
Message-ID: <Y3PLJxnvmZp35MpF@google.com> (raw)
Message-ID: <20221115172351.cxoUmBbV84-m5kcuj8o0Tj9HcVKkVzU6wv54TXVKDIw@z> (raw)
In-Reply-To: <20221115132532.GA524@willie-the-truck>

Hey Will,

On Tue, Nov 15, 2022 at 01:25:34PM +0000, Will Deacon wrote:

[...]

> On Mon, Nov 14, 2022 at 08:11:27PM +0000, Oliver Upton wrote:
> > +int kvm_pgtable_hyp_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
> > +			 struct kvm_pgtable_walker *walker);
> 
> Hmm, this feels like slightly the wrong abstraction to me -- there's nothing
> hyp-specific about the problem being solved, it's just that the only user
> is for hyp walks.
> 
> Could we instead rework 'struct kvm_pgtable' slightly so that the existing
> 'flags' field is no-longer stage-2 specific and includes a KVM_PGTABLE_LOCKED
> flag which could be set by kvm_pgtable_hyp_init()?
> 
> That way the top-level API remains unchanged and the existing callers will
> continue to work.

Thanks for the suggestion! Yeah, this should be described by the flags
instead.

We already have KVM_PGTABLE_WALK_SHARED, I could actually condition the
RCU lock/unlock on that one. That would make it an explicit opt-in
instead of requiring an opt out with callers passing KVM_PGTABLE_LOCKED.

Thoughts?

--
Thanks,
Oliver

WARNING: multiple messages have this Message-ID (diff)
From: Oliver Upton <oliver.upton@linux.dev>
To: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] KVM: arm64: Use a separate function for hyp stage-1 walks
Date: Tue, 15 Nov 2022 17:23:51 +0000	[thread overview]
Message-ID: <Y3PLJxnvmZp35MpF@google.com> (raw)
In-Reply-To: <20221115132532.GA524@willie-the-truck>

Hey Will,

On Tue, Nov 15, 2022 at 01:25:34PM +0000, Will Deacon wrote:

[...]

> On Mon, Nov 14, 2022 at 08:11:27PM +0000, Oliver Upton wrote:
> > +int kvm_pgtable_hyp_walk(struct kvm_pgtable *pgt, u64 addr, u64 size,
> > +			 struct kvm_pgtable_walker *walker);
> 
> Hmm, this feels like slightly the wrong abstraction to me -- there's nothing
> hyp-specific about the problem being solved, it's just that the only user
> is for hyp walks.
> 
> Could we instead rework 'struct kvm_pgtable' slightly so that the existing
> 'flags' field is no-longer stage-2 specific and includes a KVM_PGTABLE_LOCKED
> flag which could be set by kvm_pgtable_hyp_init()?
> 
> That way the top-level API remains unchanged and the existing callers will
> continue to work.

Thanks for the suggestion! Yeah, this should be described by the flags
instead.

We already have KVM_PGTABLE_WALK_SHARED, I could actually condition the
RCU lock/unlock on that one. That would make it an explicit opt-in
instead of requiring an opt out with callers passing KVM_PGTABLE_LOCKED.

Thoughts?

--
Thanks,
Oliver

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

  reply	other threads:[~2022-11-15 17:24 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-14 20:11 [PATCH 0/1] KVM: arm64: Skip RCU protection for hyp stage-1 Oliver Upton
2022-11-14 20:11 ` Oliver Upton
2022-11-14 20:11 ` Oliver Upton
2022-11-14 20:11 ` [PATCH 1/1] KVM: arm64: Use a separate function for hyp stage-1 walks Oliver Upton
2022-11-14 20:11   ` Oliver Upton
2022-11-14 20:11   ` Oliver Upton
2022-11-15 13:25   ` Will Deacon
2022-11-15 13:25     ` Will Deacon
2022-11-15 13:25     ` Will Deacon
2022-11-15 17:23     ` Oliver Upton [this message]
2022-11-15 17:23       ` Oliver Upton
2022-11-15 17:23       ` Oliver Upton

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