From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Hansen Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function Date: Fri, 7 Jun 2019 09:39:41 -0700 Message-ID: <00421c4e-c64b-57cf-882e-aa7b9a007661@intel.com> References: <20190606200926.4029-1-yu-cheng.yu@intel.com> <20190606200926.4029-4-yu-cheng.yu@intel.com> <20190607080832.GT3419@hirez.programming.kicks-ass.net> <76B7B1AE-3AEA-4162-B539-990EF3CCE2C2@amacapital.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <76B7B1AE-3AEA-4162-B539-990EF3CCE2C2@amacapital.net> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Andy Lutomirski , Yu-cheng Yu Cc: Peter Zijlstra , x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit List-Id: linux-api@vger.kernel.org On 6/7/19 9:35 AM, Andy Lutomirski wrote: > One might reasonably wonder why this state is privileged in the first > place and, given that, why we’re allowing it to be written like > this. I think it's generally a good architectural practice to make things like this privileged. They're infrequent so can survive the cost of a trip in/out of the kernel and are a great choke point to make sure the OS is involved. I wish we had the same for MPX or pkeys per-task "setup".