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Fri, 17 Jul 2020 09:17:22 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 163AB3003D8; Fri, 17 Jul 2020 11:17:19 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0035129CF6F50; Fri, 17 Jul 2020 11:17:18 +0200 (CEST) Date: Fri, 17 Jul 2020 11:17:18 +0200 From: Peter Zijlstra To: ira.weiny@intel.com Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , x86@kernel.org, Dave Hansen , Dan Williams , Vishal Verma , Andrew Morton , Fenghua Yu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH RFC V2 12/17] memremap: Add zone device access protection Message-ID: <20200717091718.GA10769@hirez.programming.kicks-ass.net> References: <20200717072056.73134-1-ira.weiny@intel.com> <20200717072056.73134-13-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200717072056.73134-13-ira.weiny@intel.com> X-Rspamd-Queue-Id: 7019B181B84E6 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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 Fri, Jul 17, 2020 at 12:20:51AM -0700, ira.weiny@intel.com wrote: > +void dev_access_disable(void) > +{ > + unsigned long flags; > + > + if (!static_branch_unlikely(&dev_protection_static_key)) > + return; > + > + local_irq_save(flags); > + current->dev_page_access_ref--; > + if (current->dev_page_access_ref == 0) if (!--current->dev_page_access_ref) > + pks_update_protection(dev_page_pkey, PKEY_DISABLE_ACCESS); > + local_irq_restore(flags); > +} > +EXPORT_SYMBOL_GPL(dev_access_disable); > + > +void dev_access_enable(void) > +{ > + unsigned long flags; > + > + if (!static_branch_unlikely(&dev_protection_static_key)) > + return; > + > + local_irq_save(flags); > + /* 0 clears the PKEY_DISABLE_ACCESS bit, allowing access */ > + if (current->dev_page_access_ref == 0) > + pks_update_protection(dev_page_pkey, 0); > + current->dev_page_access_ref++; if (!current->dev_page_access_ref++) > + local_irq_restore(flags); > +} > +EXPORT_SYMBOL_GPL(dev_access_enable); Also, you probably want something like: static __always_inline devm_access_disable(void) { if (static_branch_unlikely(&dev_protection_static_key)) __devm_access_disable(); } static __always_inline devm_access_enable(void) { if (static_branch_unlikely(&dev_protection_static_key)) __devm_access_enable(); }