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dkim=pass header.d=citrix.com header.s=securemail header.b=SXuQ9+qa; dkim=pass header.d=citrix.onmicrosoft.com header.s=selector2-citrix-onmicrosoft-com header.b=RqRSAEZU; dmarc=pass (policy=reject) header.from=citrix.com; spf=none (imf08.hostedemail.com: domain of Andrew.Cooper3@citrix.com has no SPF policy when checking 216.71.155.175) smtp.mailfrom=Andrew.Cooper3@citrix.com X-HE-Tag: 1635160439-368524 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 25/10/2021 11:59, Peter Zijlstra wrote: > On Thu, Oct 21, 2021 at 05:21:10AM -0700, Nadav Amit wrote: >> From: Nadav Amit >> Add a check to prevent access_error() from returning mistakenly that >> page-faults due to instruction fetch are not allowed. Intel SDM does not >> indicate whether "instruction fetch" and "write" in the hardware error >> code are mutual exclusive, so check both before returning whether the >> access is allowed. > Dave, can we get that clarified? It seems a bit naf and leads to > confusing code IMO. There is no such thing as an instruction fetch (a read) causing a modification to the mapping.=C2=A0 From this point of view, you'd never expect to see them both set. However, be aware that INSTR is only reported for NX || SMEP.=C2=A0 Without either, instruction vs data accesses are distinguished internally (can be demonstrated with SMAP) but not visible in the pagefault error code. ~Andrew