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 5A4A9C0032E for ; Wed, 25 Oct 2023 08:05:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233065AbjJYIFE (ORCPT ); Wed, 25 Oct 2023 04:05:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40554 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230147AbjJYIFD (ORCPT ); Wed, 25 Oct 2023 04:05:03 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33EB091 for ; Wed, 25 Oct 2023 01:05:02 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81F4AC433C7; Wed, 25 Oct 2023 08:05:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1698221101; bh=iSkD8tZvQK6fMOgU/tZVlBiEwFdIr6jy+fjpc6gQDTw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=mlB0h8InEChKt3EO1uzCZjqEjlt27/GfC5rSJHBS2pL7VO7B8N0Okbrt9mMHmBybz YgrnK1gzARKA2T05KSKw/ZyWlOMCBKPKekOKs7TBufsaS45VuwmTV4mUwlqUTB+erN /8/Kojb1q0qBrdWmzrEJ84/uvtQT84ecH64indJu/vVQ74c/7eT4SznOuOnC2RrGuF zRgpN1Hs03A72sLOkRWhSPpXSnwUQXm7uIB7+VKfwahvolIj6RO04/KRY1pQI8zpIf cn4mfUs5F4snvDhm+nREcTHLChpcyGnuMjsvDM3fwIDqOZ4Z3x8d2PxhHVVYtXQqs4 LlrWDMSiKdFEw== 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 1qvYst-007TE8-20; Wed, 25 Oct 2023 09:04:59 +0100 Date: Wed, 25 Oct 2023 09:04:58 +0100 Message-ID: <86il6v3z6d.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: <20231024210739.1729723-1-oliver.upton@linux.dev> References: <20231024210739.1729723-1-oliver.upton@linux.dev> 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 Tue, 24 Oct 2023 22:07:39 +0100, Oliver Upton wrote: > > It is a pretty well known fact that KVM does not support MMIO emulation > without valid instruction syndrome information (ESR_EL2.ISV == 0). The > dmesg is useless as it provides zero context and just winds up polluting > logs. Let's just delete it. > > Any userspace that cares should just use KVM_CAP_ARM_NISV_TO_USER, which > inherently ties to a vCPU context. > > Signed-off-by: Oliver Upton > --- > arch/arm64/kvm/mmio.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/arm64/kvm/mmio.c b/arch/arm64/kvm/mmio.c > index 3dd38a151d2a..a53721be32ec 100644 > --- a/arch/arm64/kvm/mmio.c > +++ b/arch/arm64/kvm/mmio.c > @@ -143,7 +143,6 @@ int io_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa) > return 0; > } > > - kvm_pr_unimpl("Data abort outside memslots with no valid syndrome info\n"); > return -ENOSYS; > } > > 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. Thanks, M. -- Without deviation from the norm, progress is not possible.