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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id i72si5551863pfi.52.2019.02.13.05.17.14 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 13 Feb 2019 05:17:15 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=ROpBr8h6; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=g258Euwx0GrLQtKmSvWxw0CICp9PokNV4/Yv5ookS90=; b=ROpBr8h67o5e75H2FUd/lLVfM u6I13qq/lEPQLC2MlT5i7JauXenxPe8ri8dIBdqxo/DGvTMJLYoVCzFUqN+H2Vt9eSmbo4znPaoSl q/RSbrkG6zw5Wj1RJ39V9tPtvnKjFE1mSUrxzLsFSkhZxpDZWUZlGEPGtuhwcSUSzhigALi7YVRQF CNRHjkBeMsihplz7JRmDydJHk5jdbbUwDVZkQd0QPEkw1AJrmfoasfW/B6gFiOlHcfF0G7V0qxplb LTBkavhsR7gSPSjcqi2L255rWsd/oOrc4nSDmJz2HuuI7uUuXX0WyJ+/VKQQKpHZ9dkOo9LA8YoEO 1ZjGMhjjw==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gtuPW-0005n1-LV; Wed, 13 Feb 2019 13:17:10 +0000 Date: Wed, 13 Feb 2019 05:17:10 -0800 From: Matthew Wilcox To: Anshuman Khandual Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, kirill@shutemov.name, kirill.shutemov@linux.intel.com, vbabka@suse.cz, will.deacon@arm.com, catalin.marinas@arm.com, dave.hansen@intel.com Subject: Re: [RFC 1/4] mm: Introduce lazy exec permission setting on a page Message-ID: <20190213131710.GR12668@bombadil.infradead.org> References: <1550045191-27483-1-git-send-email-anshuman.khandual@arm.com> <1550045191-27483-2-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1550045191-27483-2-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.9.2 (2017-12-15) 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 Wed, Feb 13, 2019 at 01:36:28PM +0530, Anshuman Khandual wrote: > +#ifdef CONFIG_ARCH_SUPPORTS_LAZY_EXEC > +static inline pte_t maybe_mkexec(pte_t entry, struct vm_area_struct *vma) > +{ > + if (unlikely(vma->vm_flags & VM_EXEC)) > + return pte_mkexec(entry); > + return entry; > +} > +#else > +static inline pte_t maybe_mkexec(pte_t entry, struct vm_area_struct *vma) > +{ > + return entry; > +} > +#endif > +++ b/mm/memory.c > @@ -2218,6 +2218,8 @@ static inline void wp_page_reuse(struct vm_fault *vmf) > flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); > entry = pte_mkyoung(vmf->orig_pte); > entry = maybe_mkwrite(pte_mkdirty(entry), vma); > + if (vmf->flags & FAULT_FLAG_INSTRUCTION) > + entry = maybe_mkexec(entry, vma); I don't understand this bit. We have a fault based on an instruction fetch. But we're only going to _maybe_ set the exec bit? Why not call pte_mkexec() unconditionally?