From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [RFC PATCH] KVM: arm/arm64: Enable direct irqfd MSI injection Date: Mon, 18 Mar 2019 13:30:40 +0000 Message-ID: <20190318133040.1cfad9a4@why.wild-wind.fr.eu.org> References: <1552833373-19828-1-git-send-email-yuzenghui@huawei.com> <86o969z42z.wl-marc.zyngier@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: mst@redhat.com, kvm@vger.kernel.org, "Raslan, KarimAllah" , andre.przywara@arm.com, linux-kernel@vger.kernel.org, pbonzini@redhat.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org To: Zenghui Yu Return-path: In-Reply-To: <86o969z42z.wl-marc.zyngier@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On Sun, 17 Mar 2019 19:35:48 +0000 Marc Zyngier 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.