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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A63DC25B47 for ; Wed, 25 Oct 2023 08:41:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229743AbjJYIlJ (ORCPT ); Wed, 25 Oct 2023 04:41:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232213AbjJYIlH (ORCPT ); Wed, 25 Oct 2023 04:41:07 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 86B0D123 for ; Wed, 25 Oct 2023 01:41:05 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FD85C433C8; Wed, 25 Oct 2023 08:41:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698223265; bh=kS4WC9/dNdK23vM/SwjlhJSsb9qRY+exIRoHLX8ec/4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=L/8ySrYzFojPM9p646qXwYkTTeGNaow6NjV7CfBLqoGwU6wnGGYCLeJenM363cncK Yp24Izc6GYWhW69h87azBGnyncESgO7LfG3JdkB8mct0CM/T/XT6k3vYoFwH4qo0Zy UqoND+3jDj6IV/jZYyGlgX3kryCTkJJgt4TXB9lv/LS57VfIO+CfbKzpq3fSO3o0Ny oA7cB7noRUMCNBLzbmXlfrbjBbCNKYP1CBenLE5pQtyLho2jBvTeWRxuQbdXgPhjOK D+J5Dvky43lwzwd8RB8+nlWUQQ+j0NMYcarFGPqHTZq3rmmxp6BS56GhGdS6dXyBuK 6grkoQjXiDnHg== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qvZRm-007TuR-OF; Wed, 25 Oct 2023 09:41:02 +0100 Date: Wed, 25 Oct 2023 09:41:01 +0100 Message-ID: <86fs1z3xia.wl-maz@kernel.org> From: Marc Zyngier To: Oliver Upton Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, James Morse , Suzuki K Poulose , Zenghui Yu Subject: Re: [PATCH] KVM: arm64: Stop printing about MMIO accesses where ISV==0 In-Reply-To: References: <20231024210739.1729723-1-oliver.upton@linux.dev> <86il6v3z6d.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/29.1 (aarch64-unknown-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: 185.219.108.64 X-SA-Exim-Rcpt-To: oliver.upton@linux.dev, kvmarm@lists.linux.dev, kvm@vger.kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com 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: kvm@vger.kernel.org On Wed, 25 Oct 2023 09:25:07 +0100, Oliver Upton wrote: > > On Wed, Oct 25, 2023 at 09:04:58AM +0100, Marc Zyngier wrote: > > [...] > > > While I totally agree that this *debug* statement should go, we should > > also replace it with something else. > > > > Because when you're trying to debug a guest (or even KVM itself), > > seeing this message is a sure indication that the guest is performing > > an access outside of memory. The fact that KVM tries to handle it as > > MMIO is just an implementation artefact. > > > > So I'd very much welcome a replacement tracepoint giving a bit more > > information, such as guest PC, IPA being accessed, load or store. With > > that, everybody wins. > > Aren't we already covered by the kvm_guest_fault tracepoint? Userspace > can filter events on ESR to get the faults it cares about. I'm not > against adding another tracepoint, but in my experience kvm_guest_fault > has been rather useful for debugging any type of guest fault. That tracepoint is one of the most triggered, and sifting through this is a painful experience. If we go down that road, adding a bit of extra documentation (pointed to from the KVM_RUN entry) and an example filter script would be most useful. Thanks, M. -- Without deviation from the norm, progress is not possible.