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Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, Yu-cheng Yu Subject: Re: [PATCH v5 11/39] x86/mm: Update pte_modify for _PAGE_COW Message-ID: References: <20230119212317.8324-1-rick.p.edgecombe@intel.com> <20230119212317.8324-12-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230119212317.8324-12-rick.p.edgecombe@intel.com> X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 8d4i778ug74brtwopqeymh1bk3pkon94 X-Rspamd-Queue-Id: 46C22120029 X-HE-Tag: 1675952194-945612 X-HE-Meta: U2FsdGVkX18FGmwjoSSIN3loCHxr10qymjJMLQ6D245/Bpgo+WL56SpFKS+Ri0i5KYQm+UIV57JgPXv+WbGjCzmpcEhqgcRNwqVP2nyYosefoixEKFHENtiMjpfbJl+6VjKhXZ/bVtfVIlY1Ozf63/sC/Vch6grlwwRwOSGqMEXExNpoqNRo50xZxjiuZg44RZZIYmfMmgvC81Zj7WxGAnY4se6k/0qMRBchHVTkOD3QVJvV6ojW6gpS8Q4Ydf/YTdszIKzVv7bXfb2SYpunjOXv+AP73Z7lZX7wPyNiaKcTX0hFKb9Sfdh1BQK2PEHZYcnIrT7adyGBwpCU9c/lRTQIEaZAxMvByo7UFpNvp1dLxPwdlZgGlx2710WH6ywK5PaJwAqRRuXnfG+Ma0hgLiSNMZTP54ldPxtTATZ6Gew9kr2q5bXEb9dkCTEzFvQz0ySM95gcvFNxmfYfkLOAfhmMuMKgNGZRWbmqE6lUVQMUkvMXdJ93zenklKQMCyBq/dHFKh7bnsolB7Bby2Dvk0d4qfXKvE+7a5g/NriVXzXlp8xuqTXmUaFdhJZ5OCvg1ASGoiJfdDoQu5ZU6YOCUL8KfKbAcPXd+CKzk/MdwNSAL78TmyLv2+Su1rsxHOEUowcR3TDKBfeIQc86d/v5W5AGtEjoq1ouYnBfrFci1xGW0KRlCNQWL0lDASgR56zIHbwegbwYf8SKeXRaz/6OCHnv0X0rR3zryKs/+uNBo43BWWMvQDqB6ma/VCoR+IvfT4TE3QUlFj94EionijnBSGIG3vjCMqlU1dmBZa/hovPtQQSqjsla+PaJJeQzOLIi0PMKgwfGahHvWi+GsVgGuczw62dVHKtDgFTuIhA3tgc72iow5raRDKtsdSJIJz2klSy7FipWuj40upKu5/1qxZM5dXHXPWk7cusAPQI87tM5XTBhmHRYqemyMz3k6dUWw/SOS3jJO1tUBCEf5Eu AOy6mqsG uKwcO+vWoryMSdomwzYGbhH4l9V47/Q7nMAev3WXWik5dokmt1HOUIhTjKhaPb8XnvfWUNiorKB/ek4HaEXsNG/HA5MJLy8/bOR1XkKrKMWArgR7r52v8UQfOj4pQ4WxnFDD/qvpTEuPW5SdrbyDsD89ZO7R3l505qVEqwnqX73rr7zVPvkXqcLKeRUbWxkbUCCr/GGKuP1D79++oo1fhjThfQ875xfY1n/mOMQixZN0zwCgwMmgkp/AUMbFRxdJrMwRw5OISbuk9aD0dixPtP429fTkCGmgc5rI+/k0VBCjz8lsLrolmhTgIZ+i2AVQNnVJgSMXrZwHIIGwCH3s2dkD/ymxcvPJZXDuy 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, Jan 19, 2023 at 01:22:49PM -0800, Rick Edgecombe wrote: > From: Yu-cheng Yu > > The Write=0,Dirty=1 PTE has been used to indicate copy-on-write pages. > However, newer x86 processors also regard a Write=0,Dirty=1 PTE as a > shadow stack page. In order to separate the two, the software-defined > _PAGE_DIRTY is changed to _PAGE_COW for the copy-on-write case, and > pte_*() are updated to do this. "In order to separate the two, change the software-defined ..." >From section "2) Describe your changes" in Documentation/process/submitting-patches.rst: "Describe your changes in imperative mood, e.g. "make xyzzy do frotz" instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy to do frotz", as if you are giving orders to the codebase to change its behaviour." > +static inline pte_t __pte_mkdirty(pte_t pte, bool soft) > +{ > + pteval_t dirty = _PAGE_DIRTY; > + > + if (soft) > + dirty |= _PAGE_SOFT_DIRTY; > + > + return pte_set_flags(pte, dirty); > +} Dunno, do you even need that __pte_mkdirty() helper? AFAIU, pte_mkdirty() will always set _PAGE_SOFT_DIRTY too so whatever the __pte_mkdirty() thing needs to do, you can simply do it by foot in the two callsites. And this way you won't have the confusion: should I use pte_mkdirty() or __pte_mkdirty()? Ditto for the pmd variants. Otherwise, this is starting to make more sense now. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette