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Shutemov" To: "Edgecombe, Rick P" Cc: "peterz@infradead.org" , "Lutomirski, Andy" , "dave.hansen@linux.intel.com" , "linux-kernel@vger.kernel.org" , "hjl.tools@gmail.com" , "linux-mm@kvack.org" , "kcc@google.com" , "andreyknvl@gmail.com" , "ak@linux.intel.com" , "dvyukov@google.com" , "x86@kernel.org" , "ryabinin.a.a@gmail.com" , "glider@google.com" Subject: Re: [PATCHv3 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED_ADDR Message-ID: <20220610180635.l44opq2votd3gxpl@black.fi.intel.com> References: <20220610143527.22974-1-kirill.shutemov@linux.intel.com> <20220610143527.22974-7-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-5.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_NONE,T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 10, 2022 at 04:16:01PM +0000, Edgecombe, Rick P wrote: > On Fri, 2022-06-10 at 17:35 +0300, Kirill A. Shutemov wrote: > > +static int prctl_enable_tagged_addr(unsigned long nr_bits) > > +{ > > + struct mm_struct *mm = current->mm; > > + > > + /* Already enabled? */ > > + if (mm->context.lam_cr3_mask) > > + return -EBUSY; > > + > > + /* LAM has to be enabled before spawning threads */ > > + if (get_nr_threads(current) > 1) > > + return -EBUSY; > > Does this work for vfork()? I guess the idea is that locking is not > needed below because there is only one thread with the MM, but with > vfork() another task could operate on the MM, call fork(), etc. I'm not > sure... I'm not sure I follow. vfork() blocks parent process until child exit or execve(). I don't see how it is a problem. -- Kirill A. Shutemov