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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id n3sm6548548wmf.46.2019.02.13.00.14.52 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 13 Feb 2019 00:14:52 -0800 (PST) Date: Wed, 13 Feb 2019 09:14:50 +0100 From: Ingo Molnar To: Fenghua Yu Cc: Thomas Gleixner , Ingo Molnar , H Peter Anvin , Dave Hansen , Ashok Raj , Peter Zijlstra , Michael Chan , Ravi V Shankar , Ricardo Neri , linux-kernel , x86 Subject: Re: [PATCH v3 10/10] x86/split_lock: Handle #AC exception for split lock Message-ID: <20190213081450.GA53242@gmail.com> References: <1549084491-57808-1-git-send-email-fenghua.yu@intel.com> <1549084491-57808-11-git-send-email-fenghua.yu@intel.com> <20190211105339.GA40840@gmail.com> <20190211181013.GA103371@romley-ivt3.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190211181013.GA103371@romley-ivt3.sc.intel.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Fenghua Yu wrote: > On Mon, Feb 11, 2019 at 11:53:39AM +0100, Ingo Molnar wrote: > > > + do_trap(trapnr, signr, str, regs, error_code, BUS_ADRALN, NULL); > > > + } > > > +} > > > > Is there any experience with how frequently this signal is killing > > user-space processes on a modern distro? Any expectation of how frequent > > such SIGBUS task terminations are going to be in the field? > > We did pretty intensive testing internally (zero day tests, many engineers > and testers use the patches in their dailly work, etc). So far I'm not > aware of any user space process hiting split lock issue. I guess GCC or > other compilers takes care of the issue already. Inline assembly code may > hit the issue if code is not right, but there are fewer inline assembly > code in user space. > > So far we only find two kernel split lock issues and fix them in the first > two patches in this patch set. We also find one BIOS split lock issue > internally which has been fixed in production BIOS. > > Thanks. Ok, still, for binary compatibility's sake, could you please add a sysctl knob (root-only, etc.) and a kernel boot parameter that disables this check? Looks good otherwise. Thanks, Ingo