From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH] KVM: arm/arm64: Remove struct vgic_irq pending field Date: Mon, 23 Jan 2017 17:06:50 +0100 Message-ID: <20170123160650.GF15850@cbox> References: <20170123133951.10329-1-christoffer.dall@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E71D340296 for ; Mon, 23 Jan 2017 11:06:53 -0500 (EST) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 4TCFn1d2KDqx for ; Mon, 23 Jan 2017 11:06:51 -0500 (EST) Received: from mail-lf0-f51.google.com (mail-lf0-f51.google.com [209.85.215.51]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 3F59340190 for ; Mon, 23 Jan 2017 11:06:51 -0500 (EST) Received: by mail-lf0-f51.google.com with SMTP id z134so95961577lff.3 for ; Mon, 23 Jan 2017 08:06:56 -0800 (PST) Content-Disposition: inline In-Reply-To: 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 To: Marc Zyngier Cc: Andre Przywara , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org List-Id: kvmarm@lists.cs.columbia.edu On Mon, Jan 23, 2017 at 03:44:16PM +0000, Marc Zyngier wrote: > On 23/01/17 13:39, Christoffer Dall wrote: > > One of the goals behind the VGIC redesign was to get rid of cached or > > intermediate state in the data structures, but we decided to allow > > ourselves to precompute the pending value of an IRQ based on the line > > level and pending latch state. However, this has now become difficult > > to base proper GICv3 save/restore on, because there is a potential to > > modify the pending state without knowing if an interrupt is edge or > > level configured. > > > > See the following post and related message for more background: > > https://lists.cs.columbia.edu/pipermail/kvmarm/2017-January/023195.html > > > > This commit gets rid of the precomputed pending field in favor of a > > function that calculates the value when needed, irq_is_pending(). > > > > The soft_pending field is renamed to pending_latch to represent that > > this latch is the equivalent hardware latch which gets manipulated by > > the input signal for edge-triggered interrupts and when writing to the > > SPENDR/CPENDR registers. > > > > After this commit save/restore code should be able to simply restore the > > pending_latch state, line_level state, and config state in any order and > > get the desired result. > > > > Signed-off-by: Christoffer Dall > > I admit having lost a few brain cells looking at this patch, and I can't > prove it wrong! ;-) I like the fact that it now provides a safe > abstraction to the pending state, and that there is exactly *one* place > where line_level is evaluated. > > Reviewed-by: Marc Zyngier > Thanks! I suppose looking at this again, I don't need the "irq_set_pending_latch()" indirection but I can just set this variable directly. What do you think? Would it be cleaner? -Christoffer