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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id x68sm50341qka.129.2020.04.09.14.28.46 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 09 Apr 2020 14:28:46 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.80.23.2.2\)) Subject: Re: KCSAN + KVM = host reset From: Qian Cai In-Reply-To: Date: Thu, 9 Apr 2020 17:28:45 -0400 Cc: Paolo Bonzini , "paul E. McKenney" , kasan-dev , LKML , kvm@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <017E692B-4791-46AD-B9ED-25B887ECB56B@lca.pw> <2730C0CC-B8B5-4A65-A4ED-9DFAAE158AA6@lca.pw> To: Marco Elver X-Mailer: Apple Mail (2.3608.80.23.2.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Apr 9, 2020, at 12:03 PM, Marco Elver wrote: >=20 > On Thu, 9 Apr 2020 at 17:30, Qian Cai wrote: >>=20 >>=20 >>=20 >>> On Apr 9, 2020, at 11:22 AM, Marco Elver wrote: >>>=20 >>> On Thu, 9 Apr 2020 at 17:10, Qian Cai wrote: >>>>=20 >>>>=20 >>>>=20 >>>>> On Apr 9, 2020, at 3:03 AM, Marco Elver wrote: >>>>>=20 >>>>> On Wed, 8 Apr 2020 at 23:29, Qian Cai wrote: >>>>>>=20 >>>>>>=20 >>>>>>=20 >>>>>>> On Apr 8, 2020, at 5:25 PM, Paolo Bonzini = wrote: >>>>>>>=20 >>>>>>> On 08/04/20 22:59, Qian Cai wrote: >>>>>>>> Running a simple thing on this AMD host would trigger a reset = right away. >>>>>>>> Unselect KCSAN kconfig makes everything work fine (the host = would also >>>>>>>> reset If only "echo off > /sys/kernel/debug/kcsan=E2=80=9D = before running qemu-kvm). >>>>>>>=20 >>>>>>> Is this a regression or something you've just started to play = with? (If >>>>>>> anything, the assembly language conversion of the AMD world = switch that >>>>>>> is in linux-next could have reduced the likelihood of such a = failure, >>>>>>> not increased it). >>>>>>=20 >>>>>> I don=E2=80=99t remember I had tried this combination before, so = don=E2=80=99t know if it is a >>>>>> regression or not. >>>>>=20 >>>>> What happens with KASAN? My guess is that, since it also happens = with >>>>> "off", something that should not be instrumented is being >>>>> instrumented. >>>>=20 >>>> No, KASAN + KVM works fine. >>>>=20 >>>>>=20 >>>>> What happens if you put a 'KCSAN_SANITIZE :=3D n' into >>>>> arch/x86/kvm/Makefile? Since it's hard for me to reproduce on this >>>>=20 >>>> Yes, that works, but this below alone does not work, >>>>=20 >>>> KCSAN_SANITIZE_kvm-amd.o :=3D n >>>=20 >>> There are some other files as well, that you could try until you hit >>> the right one. >>>=20 >>> But since this is in arch, 'KCSAN_SANITIZE :=3D n' wouldn't be too = bad >>> for now. If you can't narrow it down further, do you want to send a >>> patch? >>=20 >> No, that would be pretty bad because it will disable KCSAN for Intel >> KVM as well which is working perfectly fine right now. It is only AMD >> is broken. >=20 > Interesting. Unfortunately I don't have access to an AMD machine right = now. >=20 > Actually I think it should be: >=20 > KCSAN_SANITIZE_svm.o :=3D n > KCSAN_SANITIZE_pmu_amd.o :=3D n >=20 > If you want to disable KCSAN for kvm-amd. KCSAN_SANITIZE_svm.o :=3D n That alone works fine. I am wondering which functions there could = trigger perhaps some kind of recursing with KCSAN?=