From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: kvm: WARNING in em_jmp_far Date: Tue, 15 Nov 2016 11:45:26 +0100 Message-ID: References: <45DE3A97-304D-4D1A-AADE-1B9D154BB7DF@gmail.com> <2C688876-3784-4852-AD7D-0E6548F5F4FF@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: syzkaller , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "x86@kernel.org" , KVM list , LKML , Steve Rutherford , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= To: Nadav Amit , Dmitry Vyukov Return-path: In-Reply-To: <2C688876-3784-4852-AD7D-0E6548F5F4FF@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 15/11/2016 06:39, Nadav Amit wrote: > >> On Nov 14, 2016, at 9:30 PM, Dmitry Vyukov wrote: >> >> On Tue, Nov 15, 2016 at 6:24 AM, Nadav Amit wrote: >>> >>>> On Nov 14, 2016, at 9:06 PM, Dmitry Vyukov wrote: >>>> >>>> Hello, >>>> >>>> The following program triggers WARNING in em_jmp_far: >>>> https://gist.githubusercontent.com/dvyukov/16bfd3d68fa7d5461101ef74e07796e4/raw/e6d663980681f2c5838ff6cd361cede7d3204838/gistfile1.txt >>>> >>>> >>>> WARNING: CPU: 1 PID: 15748 at arch/x86/kvm/emulate.c:2128 em_jmp_far+0x4a7/0x530 >>> >>> I don’t know how to “read” the test, but it seems that this warning >>> can be triggered if CS base/limit cause a #GP exception when EIP >>> is loaded. >>> >>> I think it safe to remove this warning (which I introduced) as well as >>> the redundant “return rc” that follows it. The code should handle the >>> emulation correctly regardless of the warning. >> >> There was also a similar WARNING in em_ret_far: >> https://groups.google.com/forum/#!msg/syzkaller/o5ZftARBhrs/r1ivQ-HtBgAJ >> >> Please mail a fix and add a test. > > I am sorry, but I don’t think my current employer allows me to contribute > to KVM in such a manner. No problem, we can take care of it. Paolo