From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Date: Mon, 27 Oct 2014 20:36:53 +0000 Subject: RE: [PATCH v9 09/12] x86, mpx: decode MPX instruction to get bound violation information Message-Id: List-Id: References: <1413088915-13428-1-git-send-email-qiaowei.ren@intel.com> <1413088915-13428-10-git-send-email-qiaowei.ren@intel.com> <9E0BE1322F2F2246BD820DA9FC397ADE0180ED16@shsmsx102.ccr.corp.intel.com> In-Reply-To: <9E0BE1322F2F2246BD820DA9FC397ADE0180ED16@shsmsx102.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Ren, Qiaowei" Cc: "H. Peter Anvin" , Ingo Molnar , "Hansen, Dave" , "x86@kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "linux-ia64@vger.kernel.org" , "linux-mips@linux-mips.org" On Mon, 27 Oct 2014, Ren, Qiaowei wrote: > On 2014-10-24, Thomas Gleixner wrote: > > On Sun, 12 Oct 2014, Qiaowei Ren wrote: > > > >> This patch sets bound violation fields of siginfo struct in #BR > >> exception handler by decoding the user instruction and constructing > >> the faulting pointer. > >> > >> This patch does't use the generic decoder, and implements a limited > >> special-purpose decoder to decode MPX instructions, simply because > >> the generic decoder is very heavyweight not just in terms of > >> performance but in terms of interface -- because it has to. > > > > My question still stands why using the existing decoder is an issue. > > Performance is a complete non issue in case of a bounds violation and > > the interface argument is just silly, really. > > > > As hpa said, we only need to decode several mpx instructions > including BNDCL/BNDCU, and general decoder looks like a little > heavy. Peter, what do you think about it? You're repeating yourself. Care to read the discussion about this from the last round of review again? Thanks, tglx