From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marc Zyngier <marc.zyngier@arm.com>
Subject: Re: [RFC PATCH] KVM: arm/arm64: Enable direct irqfd MSI injection
Date: Mon, 18 Mar 2019 13:30:40 +0000
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To: Zenghui Yu <yuzenghui@huawei.com>
Cc: mst@redhat.com, kvm@vger.kernel.org, "Raslan,
 KarimAllah" <karahmed@amazon.de>, andre.przywara@arm.com, linux-kernel@vger.kernel.org, pbonzini@redhat.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org
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On Sun, 17 Mar 2019 19:35:48 +0000
Marc Zyngier <marc.zyngier@arm.com> wrote:

[...]

> A first approach would be to keep a small cache of the last few
> successful translations for this ITS, cache that could be looked-up by
> holding a spinlock instead. A hit in this cache could directly be
> injected. Any command that invalidates or changes anything (DISCARD,
> INV, INVALL, MAPC with V=0, MAPD with V=0, MOVALL, MOVI) should nuke
> the cache altogether.

And to explain what I meant with this, I've pushed a branch[1] with a
basic prototype. It is good enough to get a VM to boot, but I wouldn't
trust it for anything serious just yet.

If anyone feels like giving it a go and check whether it has any
benefit performance wise, please do so.

Thanks,

	M.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/its-translation-cache
-- 
Without deviation from the norm, progress is not possible.