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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id s27si2026722pgm.501.2019.02.14.02.56.45 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 14 Feb 2019 02:56:45 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of peterz@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=Hn6IfzZR; spf=pass (google.com: best guess record for domain of peterz@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=peterz@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=h87IdZdCVuSbWdFagb1UhdNLjtjBoimcYpQUS+r7AhY=; b=Hn6IfzZRhdbXf7c86Xmn0Ffst WuQKta1CW47PaeEOB9FAAZC2ns5vNDz4hnZJm2czo42swIoeWSYwCdXB3mMGI6Qry1J8MSDpclLXK kdz6ZPsaUmrFBqSyRmLRQphHRHmsnhEVDcqVMhVVkh0pqTqFxA2MBqfOixBxtAfHMIEGMA8uShynt gEmU77M+VEv7uQg+5zFABeAGrfdRH8lpv80oGZcQfZnVI24U0lr/Z8awzWDUObdMr0qaNEriTdPnS Ovp522m8/zrSzKlu0kvLWGZ6YPvbQooP80v2TnDMFGscejdP3PxIeNCzFNyJhoD0bungED7gO6LKc AH+tdD3Nw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1guEgz-00036v-MJ; Thu, 14 Feb 2019 10:56:33 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DB8A220298375; Thu, 14 Feb 2019 11:56:31 +0100 (CET) Date: Thu, 14 Feb 2019 11:56:31 +0100 From: Peter Zijlstra To: Khalid Aziz Cc: juergh@gmail.com, tycho@tycho.ws, jsteckli@amazon.de, ak@linux.intel.com, torvalds@linux-foundation.org, liran.alon@oracle.com, keescook@google.com, akpm@linux-foundation.org, mhocko@suse.com, catalin.marinas@arm.com, will.deacon@arm.com, jmorris@namei.org, konrad.wilk@oracle.com, Juerg Haefliger , deepa.srinivasan@oracle.com, chris.hyser@oracle.com, tyhicks@canonical.com, dwmw@amazon.co.uk, andrew.cooper3@citrix.com, jcm@redhat.com, boris.ostrovsky@oracle.com, kanth.ghatraju@oracle.com, oao.m.martins@oracle.com, jmattson@google.com, pradeep.vincent@oracle.com, john.haxby@oracle.com, tglx@linutronix.de, kirill.shutemov@linux.intel.com, hch@lst.de, steven.sistare@oracle.com, labbott@redhat.com, luto@kernel.org, dave.hansen@intel.com, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Tycho Andersen , Marco Benatto Subject: Re: [RFC PATCH v8 03/14] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) Message-ID: <20190214105631.GJ32494@hirez.programming.kicks-ass.net> References: <8275de2a7e6b72d19b1cd2ec5d71a42c2c7dd6c5.1550088114.git.khalid.aziz@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8275de2a7e6b72d19b1cd2ec5d71a42c2c7dd6c5.1550088114.git.khalid.aziz@oracle.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 05:01:26PM -0700, Khalid Aziz wrote: > static inline void *kmap_atomic(struct page *page) > { > + void *kaddr; > + > preempt_disable(); > pagefault_disable(); > + kaddr = page_address(page); > + xpfo_kmap(kaddr, page); > + return kaddr; > } > #define kmap_atomic_prot(page, prot) kmap_atomic(page) > > static inline void __kunmap_atomic(void *addr) > { > + xpfo_kunmap(addr, virt_to_page(addr)); > pagefault_enable(); > preempt_enable(); > } How is that supposed to work; IIRC kmap_atomic was supposed to be IRQ-safe. > +/* Per-page XPFO house-keeping data */ > +struct xpfo { > + unsigned long flags; /* Page state */ > + bool inited; /* Map counter and lock initialized */ What's sizeof(_Bool) ? Why can't you use a bit in that flags word? > + atomic_t mapcount; /* Counter for balancing map/unmap requests */ > + spinlock_t maplock; /* Lock to serialize map/unmap requests */ > +}; Without that bool, the structure would be 16 bytes on 64bit, which seems like a good number. > +void xpfo_kmap(void *kaddr, struct page *page) > +{ > + struct xpfo *xpfo; > + > + if (!static_branch_unlikely(&xpfo_inited)) > + return; > + > + xpfo = lookup_xpfo(page); > + > + /* > + * The page was allocated before page_ext was initialized (which means > + * it's a kernel page) or it's allocated to the kernel, so nothing to > + * do. > + */ > + if (!xpfo || unlikely(!xpfo->inited) || > + !test_bit(XPFO_PAGE_USER, &xpfo->flags)) > + return; > + > + spin_lock(&xpfo->maplock); > + > + /* > + * The page was previously allocated to user space, so map it back > + * into the kernel. No TLB flush required. > + */ > + if ((atomic_inc_return(&xpfo->mapcount) == 1) && > + test_and_clear_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags)) > + set_kpte(kaddr, page, PAGE_KERNEL); > + > + spin_unlock(&xpfo->maplock); > +} > +EXPORT_SYMBOL(xpfo_kmap); > + > +void xpfo_kunmap(void *kaddr, struct page *page) > +{ > + struct xpfo *xpfo; > + > + if (!static_branch_unlikely(&xpfo_inited)) > + return; > + > + xpfo = lookup_xpfo(page); > + > + /* > + * The page was allocated before page_ext was initialized (which means > + * it's a kernel page) or it's allocated to the kernel, so nothing to > + * do. > + */ > + if (!xpfo || unlikely(!xpfo->inited) || > + !test_bit(XPFO_PAGE_USER, &xpfo->flags)) > + return; > + > + spin_lock(&xpfo->maplock); > + > + /* > + * The page is to be allocated back to user space, so unmap it from the > + * kernel, flush the TLB and tag it as a user page. > + */ > + if (atomic_dec_return(&xpfo->mapcount) == 0) { > + WARN(test_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags), > + "xpfo: unmapping already unmapped page\n"); > + set_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags); > + set_kpte(kaddr, page, __pgprot(0)); > + xpfo_flush_kernel_tlb(page, 0); > + } > + > + spin_unlock(&xpfo->maplock); > +} > +EXPORT_SYMBOL(xpfo_kunmap); And these here things are most definitely not IRQ-safe.