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[2620:137:e000::1:9]) by mx.google.com with ESMTPS id d33si1239194eda.62.2019.05.22.10.40.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 May 2019 10:40:23 -0700 (PDT) Received-SPF: neutral (google.com: 2620:137:e000::1:9 is neither permitted nor denied by best guess record for domain of davem@davemloft.net) client-ip=2620:137:e000::1:9; Authentication-Results: mx.google.com; spf=neutral (google.com: 2620:137:e000::1:9 is neither permitted nor denied by best guess record for domain of davem@davemloft.net) smtp.mailfrom=davem@davemloft.net Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::3d8]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 39F1515002414; Wed, 22 May 2019 10:40:20 -0700 (PDT) Date: Wed, 22 May 2019 10:40:19 -0700 (PDT) Message-Id: <20190522.104019.40493905027242516.davem@davemloft.net> To: rick.p.edgecombe@intel.com Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, linux-mm@kvack.org, mroos@linux.ee, mingo@redhat.com, namit@vmware.com, luto@kernel.org, bp@alien8.de, netdev@vger.kernel.org, dave.hansen@intel.com, sparclinux@vger.kernel.org Subject: Re: [PATCH v2] vmalloc: Fix issues with flush flag From: David Miller In-Reply-To: <339ef85d984f329aa66f29fa80781624e6e4aecc.camel@intel.com> References: <20190520.184336.743103388474716249.davem@davemloft.net> <339ef85d984f329aa66f29fa80781624e6e4aecc.camel@intel.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 22 May 2019 10:40:20 -0700 (PDT) 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: From: "Edgecombe, Rick P" Date: Tue, 21 May 2019 01:59:54 +0000 > On Mon, 2019-05-20 at 18:43 -0700, David Miller wrote: >> From: "Edgecombe, Rick P" >> Date: Tue, 21 May 2019 01:20:33 +0000 >> >> > Should it handle executing an unmapped page gracefully? Because >> > this >> > change is causing that to happen much earlier. If something was >> > relying >> > on a cached translation to execute something it could find the >> > mapping >> > disappear. >> >> Does this work by not mapping any kernel mappings at the beginning, >> and then filling in the BPF mappings in response to faults? > No, nothing too fancy. It just flushes the vm mapping immediatly in > vfree for execute (and RO) mappings. The only thing that happens around > allocation time is setting of a new flag to tell vmalloc to do the > flush. > > The problem before was that the pages would be freed before the execute > mapping was flushed. So then when the pages got recycled, random, > sometimes coming from userspace, data would be mapped as executable in > the kernel by the un-flushed tlb entries. If I am to understand things correctly, there was a case where 'end' could be smaller than 'start' when doing a range flush. That would definitely kill some of the sparc64 TLB flush routines.