From: cdall@linaro.org (Christoffer Dall)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 06/10] KVM: arm/arm64: Only clean the dcache on translation fault
Date: Tue, 17 Oct 2017 07:36:34 -0700 [thread overview]
Message-ID: <20171017143634.GI5886@lvm> (raw)
In-Reply-To: <210cf2dc-2566-a29b-637e-901f3dcc80b6@arm.com>
On Tue, Oct 17, 2017 at 10:34:15AM +0100, Marc Zyngier wrote:
> On 16/10/17 21:08, Christoffer Dall wrote:
> > On Mon, Oct 09, 2017 at 04:20:28PM +0100, Marc Zyngier wrote:
> >> The only case where we actually need to perform a dache maintenance
> >> is when we map the page for the first time, and subsequent permission
> >> faults do not require cache maintenance. Let's make it conditional
> >> on not being a permission fault (and thus a translation fault).
> >
> > Why do we actually need to do any dcache maintenance when faulting in a
> > page?
> >
> > Is this for the case when the stage 1 MMU is disabled, or to support
> > guest mappings using uncached attributes?
>
> These are indeed the two cases that require cleaning the dcache to PoC.
>
> > Can we do better, for example
> > by only flushing the cache if the guest MMU is disabled?
>
> The guest MMU being disabled is easy. But the uncached mapping is much
> trickier, and would involve parsing the guest page tables. Not something
> I'm really eager to implement.
>
Hmm, if the guest actually maps memory uncached, wouldn't it have to
invalidate caches itself, or is this the annoying thing where disabling
the MMU on hardware that doesn't have stage 2 would in fact always
completely bypass the cache, and therefore we have to do this work?
Sorry, I have forgotten all the details here, but wanted to make sure
we're not being overly careful.
Thanks,
-Christoffer
next prev parent reply other threads:[~2017-10-17 14:36 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-09 15:20 [PATCH 00/10] arm/arm64: KVM: limit icache invalidation to prefetch aborts Marc Zyngier
2017-10-09 15:20 ` [PATCH 01/10] KVM: arm/arm64: Split dcache/icache flushing Marc Zyngier
2017-10-16 20:07 ` Christoffer Dall
2017-10-17 8:57 ` Marc Zyngier
2017-10-17 14:28 ` Christoffer Dall
2017-10-17 14:41 ` Marc Zyngier
2017-10-16 21:35 ` Roy Franz (Cavium)
2017-10-17 6:44 ` Christoffer Dall
2017-10-09 15:20 ` [PATCH 02/10] arm64: KVM: Add invalidate_icache_range helper Marc Zyngier
2017-10-16 20:08 ` Christoffer Dall
2017-10-19 16:47 ` Will Deacon
2017-10-20 13:41 ` Marc Zyngier
2017-10-09 15:20 ` [PATCH 03/10] arm: KVM: Add optimized PIPT icache flushing Marc Zyngier
2017-10-16 20:07 ` Christoffer Dall
2017-10-17 9:26 ` Marc Zyngier
2017-10-17 14:34 ` Christoffer Dall
2017-10-09 15:20 ` [PATCH 04/10] arm64: KVM: PTE/PMD S2 XN bit definition Marc Zyngier
2017-10-16 20:07 ` Christoffer Dall
2017-10-09 15:20 ` [PATCH 05/10] KVM: arm/arm64: Limit icache invalidation to prefetch aborts Marc Zyngier
2017-10-16 20:08 ` Christoffer Dall
2017-10-09 15:20 ` [PATCH 06/10] KVM: arm/arm64: Only clean the dcache on translation fault Marc Zyngier
2017-10-16 20:08 ` Christoffer Dall
2017-10-17 9:34 ` Marc Zyngier
2017-10-17 14:36 ` Christoffer Dall [this message]
2017-10-17 14:52 ` Marc Zyngier
2017-10-09 15:20 ` [PATCH 07/10] KVM: arm/arm64: Preserve Exec permission across R/W permission faults Marc Zyngier
2017-10-16 20:08 ` Christoffer Dall
2017-10-17 11:22 ` Marc Zyngier
2017-10-17 14:46 ` Christoffer Dall
2017-10-17 15:04 ` Marc Zyngier
2017-10-09 15:20 ` [PATCH 08/10] KVM: arm/arm64: Drop vcpu parameter from coherent_{d, i}cache_guest_page Marc Zyngier
2017-10-16 20:08 ` [PATCH 08/10] KVM: arm/arm64: Drop vcpu parameter from coherent_{d,i}cache_guest_page Christoffer Dall
2017-10-09 15:20 ` [PATCH 09/10] KVM: arm/arm64: Detangle kvm_mmu.h from kvm_hyp.h Marc Zyngier
2017-10-16 20:08 ` Christoffer Dall
2017-10-09 15:20 ` [PATCH 10/10] arm: KVM: Use common implementation for all flushes to PoC Marc Zyngier
2017-10-16 20:06 ` Christoffer Dall
2017-10-17 12:40 ` Marc Zyngier
2017-10-17 14:48 ` Christoffer Dall
2017-10-16 20:59 ` [PATCH 00/10] arm/arm64: KVM: limit icache invalidation to prefetch aborts Christoffer Dall
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