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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 8E62CC2D0DB for ; Sun, 26 Jan 2020 11:56:11 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 0741B20700 for ; Sun, 26 Jan 2020 11:56:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="OS8ovI/t" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0741B20700 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 815474AF13; Sun, 26 Jan 2020 06:56:10 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org 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 lOpqljzoHeUE; Sun, 26 Jan 2020 06:56:09 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 55FF04AF33; Sun, 26 Jan 2020 06:56:09 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 33F4A4AF13 for ; Sun, 26 Jan 2020 06:56:08 -0500 (EST) 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 evIdrHyEfB3O for ; Sun, 26 Jan 2020 06:56:07 -0500 (EST) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 3ACBC4AEBF for ; Sun, 26 Jan 2020 06:56:07 -0500 (EST) 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 1030620700; Sun, 26 Jan 2020 11:56:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580039766; bh=GvIGv1MI/eOCaj0SZAXgD9vAtIzdzvrA7/ZPNS6pjW0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=OS8ovI/tIj3NExuAYPpjRFKN8Eyborjxlqh7tin9jqJwd3RXunvFkl3xo/gCMk0Po GyzYI9TDdyAWVK+uQcJVpgmQAWrrRJkmuZXA+g1dggG5zzxAh6Tj/FgGy8Fc6LXr3V T+U+WHLX3/uXLFIMlJz2sxhI4Gbz6fDEwi9XBuJg= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why) by disco-boy.misterjones.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1ivgWJ-001TX7-R1; Sun, 26 Jan 2020 11:56:03 +0000 Date: Sun, 26 Jan 2020 11:56:02 +0000 From: Marc Zyngier To: Beata Michalska Subject: Re: [PATCH 0/2] KVM: arm: fix KVM_CAP_ARM_INJECT_EXT_DABT for aarch32 guests Message-ID: <20200126115602.6e67b11b@why> In-Reply-To: References: <20200121123356.203000-1-james.morse@arm.com> Organization: Approximate X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: beata.michalska@linaro.org, james.morse@arm.com, kvmarm@lists.cs.columbia.edu X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: kvmarm@lists.cs.columbia.edu 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 Fri, 24 Jan 2020 15:39:29 +0000 Beata Michalska wrote: Hi Beata, > Hi James, > > Thanks for the fixes - they work like a charm. > > On Tue, 21 Jan 2020 at 12:34, James Morse wrote: > > > > Beata reports that KVM_CAP_ARM_INJECT_EXT_DABT doesn't do the expected > > thing for aarch32 guests. We get the wrong register layout, and weren't > > even trying to set a 'external abort' in the first place! > > > > Both patches are intended as fixes, but patch 2 is somewhat in the eye > > of the beholder. I don't know why an imp-def exception was picked... > > > On a side note - currently KVM exposes capability that is not fully supported > (till the fix gets applied) and there is no easy way for the user space to > determine whether the injection will work as expected and whether it is safe to > use it or not. Although this is addressing a problem that is not that common > (I suppose) but still it might be worth to add a way for the kernel to inform > the user-space that it is all good to go? There has been a 'similar' case in the > past with KVM_SET_USER_MEMORY_REGION, where fixes where needed > and those were announced through new caps. Now, I'm not sure if adding new > capability would be the best approach here though it seems that there is not > much of a choice? My take on this particular issue is that although the functionality is not perfectly working (far from it), it isn't completely broken (the guest does get some form of abort). Furthermore, we tend to add this kind of discovery mechanism when the userspace interface is broken, not when we have an implementation defect in the CPU emulation. The real question is whether there anything out there that would depend on such broken behaviour? Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm