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=-7.0 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 29A23C3A5A5 for ; Thu, 5 Sep 2019 08:04:13 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id AC5C5217D7 for ; Thu, 5 Sep 2019 08:04:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC5C5217D7 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 2F8DF4A500; Thu, 5 Sep 2019 04:04:12 -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 yzHSdssYqZS5; Thu, 5 Sep 2019 04:04:07 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 2920E4A558; Thu, 5 Sep 2019 04:04:07 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 725A54A558 for ; Thu, 5 Sep 2019 04:04:06 -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 JebuZwcOlLIH for ; Thu, 5 Sep 2019 04:04:01 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 249D64A500 for ; Thu, 5 Sep 2019 04:04:01 -0400 (EDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 94B5928; Thu, 5 Sep 2019 01:04:00 -0700 (PDT) Received: from big-swifty.misterjones.org (unknown [10.1.27.38]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5AA793F67D; Thu, 5 Sep 2019 01:03:58 -0700 (PDT) Date: Thu, 05 Sep 2019 09:03:50 +0100 Message-ID: <86r24vrwyh.wl-maz@kernel.org> From: Marc Zyngier To: Heinrich Schuchardt Subject: Re: [PATCH 1/1] KVM: inject data abort if instruction cannot be decoded In-Reply-To: <20190904180736.29009-1-xypron.glpk@gmx.de> References: <20190904180736.29009-1-xypron.glpk@gmx.de> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Cc: =?UTF-8?B?IkRhbmllbCBQIC4gQmVycmFuZ8OpIg==?= , linux-kernel@vger.kernel.org, Stefan Hajnoczi , 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 [Please use my kernel.org address. My arm.com address will disappear shortly] On Wed, 04 Sep 2019 19:07:36 +0100, Heinrich Schuchardt wrote: > > If an application tries to access memory that is not mapped, an error > ENOSYS, "load/store instruction decoding not implemented" may occur. > QEMU will hang with a register dump. > > Instead create a data abort that can be handled gracefully by the > application running in the virtual environment. > > Now the virtual machine can react to the event in the most appropriate > way - by recovering, by writing an informative log, or by rebooting. > > Signed-off-by: Heinrich Schuchardt > --- > virt/kvm/arm/mmio.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c > index a8a6a0c883f1..0cbed7d6a0f4 100644 > --- a/virt/kvm/arm/mmio.c > +++ b/virt/kvm/arm/mmio.c > @@ -161,8 +161,8 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run, > if (ret) > return ret; > } else { > - kvm_err("load/store instruction decoding not implemented\n"); > - return -ENOSYS; > + kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu)); > + return 1; How can you tell that the access would fault? You have no idea at that stage (the kernel doesn't know about the MMIO ranges that userspace handles). All you know is that you're faced with a memory access that you cannot emulate in the kernel. Injecting a data abort at that stage is not something that the architecture allows. If you want to address this, consider forwarding the access to userspace. You'll only need an instruction decoder (supporting T1, T2, A32 and A64) and a S1 page table walker (one per page table format, all three of them) to emulate the access (having taken care of stopping all the other vcpus to make sure there is no concurrent modification of the page tables). You'll then be able to return the result of the access back to the kernel. Of course, the best thing would be to actually fix the guest so that it doesn't use non-emulatable MMIO accesses. In general, that the sign of a bug in low-level accessors. 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