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 09079C4743E for ; Sat, 5 Jun 2021 10:15:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E29F2613D2 for ; Sat, 5 Jun 2021 10:15:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230036AbhFEKRn (ORCPT ); Sat, 5 Jun 2021 06:17:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:42534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229902AbhFEKRm (ORCPT ); Sat, 5 Jun 2021 06:17:42 -0400 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 7B98E613AA; Sat, 5 Jun 2021 10:15:54 +0000 (UTC) Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=wait-a-minute.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 1lpTLM-005dMl-5N; Sat, 05 Jun 2021 11:15:52 +0100 Date: Sat, 05 Jun 2021 11:15:51 +0100 Message-ID: <87im2sty5k.wl-maz@kernel.org> From: Marc Zyngier To: Sergey Senozhatsky Cc: Paolo Bonzini , Vitaly Kuznetsov , Peter Zijlstra , Suleiman Souhlal , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCHv2 2/2] kvm: x86: implement KVM PM-notifier In-Reply-To: References: <20210605023042.543341-1-senozhatsky@chromium.org> <20210605023042.543341-2-senozhatsky@chromium.org> <87k0n8u1nk.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") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: senozhatsky@chromium.org, pbonzini@redhat.com, vkuznets@redhat.com, peterz@infradead.org, suleiman@google.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 05 Jun 2021 11:03:40 +0100, Sergey Senozhatsky wrote: > > On (21/06/05 18:58), Sergey Senozhatsky wrote: > [..] > > > > +static int kvm_arch_suspend_notifier(struct kvm *kvm) > > > > +{ > > > > + struct kvm_vcpu *vcpu; > > > > + int i, ret; > > > > + > > > > + mutex_lock(&kvm->lock); > > > > + kvm_for_each_vcpu(i, vcpu, kvm) { > > > > + ret = kvm_set_guest_paused(vcpu); > > > > + if (ret) { > > > > + pr_err("Failed to pause guest VCPU%d: %d\n", > > > > + vcpu->vcpu_id, ret); > > > > > > Is it really a good idea to fail suspend when a guest doesn't have PV > > > time enabled? I also wonder how useful the pr_err() is, given that it > > > contains no information that would help identifying which guest failed > > > to pause. > > > > No opinion. What shall we do when we fail to suspend the VM? > > VM's watchdogs will trigger and maybe panic the system after > > resume. Panic the guest, maybe. Panic the host, surely not? You cannot decide what the guest uses or doesn't use anyway, so that's out of your hands. I don't think this should prevent the host from suspending, in any case. > For the time being kvm_set_guest_paused() errors out when > !vcpu->arch.pv_time_enabled, but this probably can change in the > future (who knows?). So shall I check vcpu->arch.pv_time_enabled in > kvm_arch_suspend_notifier()? That, or check for the -EINVAL return value. M. -- Without deviation from the norm, progress is not possible.