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[213.95.11.211]) by mx.google.com with ESMTPS id m1si2274885wmg.171.2019.02.14.09.44.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Feb 2019 09:44:52 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by newverein.lst.de (Postfix, from userid 2407) id 5C65B6FA8C; Thu, 14 Feb 2019 18:44:51 +0100 (CET) Date: Thu, 14 Feb 2019 18:44:51 +0100 From: Christoph Hellwig To: Khalid Aziz Cc: Christoph Hellwig , 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, steven.sistare@oracle.com, labbott@redhat.com, luto@kernel.org, dave.hansen@intel.com, peterz@infradead.org, 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 Subject: Re: [RFC PATCH v8 04/14] swiotlb: Map the buffer if it was unmapped by XPFO Message-ID: <20190214174451.GA3338@lst.de> References: <20190214074747.GA10666@lst.de> <3c75c46c-2a5a-cd75-83d4-f77d96d22f7d@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3c75c46c-2a5a-cd75-83d4-f77d96d22f7d@oracle.com> User-Agent: Mutt/1.5.17 (2007-11-01) 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 Thu, Feb 14, 2019 at 09:56:24AM -0700, Khalid Aziz wrote: > On 2/14/19 12:47 AM, Christoph Hellwig wrote: > > On Wed, Feb 13, 2019 at 05:01:27PM -0700, Khalid Aziz wrote: > >> +++ b/kernel/dma/swiotlb.c > >> @@ -396,8 +396,9 @@ static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr, > >> { > >> unsigned long pfn = PFN_DOWN(orig_addr); > >> unsigned char *vaddr = phys_to_virt(tlb_addr); > >> + struct page *page = pfn_to_page(pfn); > >> > >> - if (PageHighMem(pfn_to_page(pfn))) { > >> + if (PageHighMem(page) || xpfo_page_is_unmapped(page)) { > > > > I think this just wants a page_unmapped or similar helper instead of > > needing the xpfo_page_is_unmapped check. We actually have quite > > a few similar construct in the arch dma mapping code for architectures > > that require cache flushing. > > As I am not the original author of this patch, I am interpreting the > original intent. I think xpfo_page_is_unmapped() was added to account > for kernel build without CONFIG_XPFO. xpfo_page_is_unmapped() has an > alternate definition to return false if CONFIG_XPFO is not defined. > xpfo_is_unmapped() is cleaned up further in patch 11 ("xpfo, mm: remove > dependency on CONFIG_PAGE_EXTENSION") to a one-liner "return > PageXpfoUnmapped(page);". xpfo_is_unmapped() can be eliminated entirely > by adding an else clause to the following code added by that patch: The point I'm making it that just about every PageHighMem() check before code that does a kmap* later needs to account for xpfo as well. So instead of opencoding the above, be that using xpfo_page_is_unmapped or PageXpfoUnmapped, we really need one self-describing helper that checks if a page is unmapped for any reason and needs a kmap to access it.