From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AAE84C12002 for ; Wed, 21 Jul 2021 11:08:27 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 1986E60D07 for ; Wed, 21 Jul 2021 11:08:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1986E60D07 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id AFF0B4B0DB; Wed, 21 Jul 2021 07:08:26 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu 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 w4cUvK4AWCoL; Wed, 21 Jul 2021 07:08:25 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 925594B0E8; Wed, 21 Jul 2021 07:08:25 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id F0BF24B0DF for ; Wed, 21 Jul 2021 07:08:23 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu 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 IiEvMqD97ZOX for ; Wed, 21 Jul 2021 07:08:22 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 041304B0DB for ; Wed, 21 Jul 2021 07:08:21 -0400 (EDT) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0A05960720; Wed, 21 Jul 2021 11:08:21 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1m6A5K-00F2Hh-S3; Wed, 21 Jul 2021 12:08:19 +0100 Date: Wed, 21 Jul 2021 12:08:18 +0100 Message-ID: <87a6mf3owt.wl-maz@kernel.org> From: Marc Zyngier To: Sergey Senozhatsky Subject: Re: [PATCHv2 4/4] arm64: add host pv-vcpu-state support In-Reply-To: References: <20210709043713.887098-1-senozhatsky@chromium.org> <20210709043713.887098-5-senozhatsky@chromium.org> <874kcz33g5.wl-maz@kernel.org> <87h7go2h69.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: senozhatsky@chromium.org, joelaf@google.com, will@kernel.org, suleiman@google.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: Joel Fernandes , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Suleiman Souhlal , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Wed, 21 Jul 2021 11:38:40 +0100, Sergey Senozhatsky wrote: > > On (21/07/21 09:40), Marc Zyngier wrote: > > > > > > Can that be cured by just checking vcpu->preempted before calling > > > kvm_update_vcpu_preempted() ? > > > > It isn't obvious to me that this is the right thing to do. > > vcpu->preempted is always updated on sched-out from the preempt > > notifier if the vcpu was on the run-queue, so my guess is that it will > > always be set when switching to another task. > > > > What you probably want is to check whether the vcpu is blocked by > > introspecting the wait-queue with: > > > > scuwait_active(kvm_arch_vcpu_get_wait(vcpu) > > > > which will tell you whether you are blocking or not. We are already > > using a similar construct for arming a background timer in this case. > > Can we examine if vcpu->run->exit_reason == WFE/WFI and avoid setting > preempted state if so? We never go back to userspace for WFI/WFE, so no reason to populate the run structure. Checking for the blocked state is the right thing to do, and we already have the primitive for this. Just use it. M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm