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Thu, 07 Mar 2024 15:37:40 -0800 (PST) MIME-Version: 1.0 References: <20240307133916.3782068-1-yosryahmed@google.com> <20240307133916.3782068-2-yosryahmed@google.com> <56ea29c2-8545-4689-a418-eb7784613650@intel.com> In-Reply-To: <56ea29c2-8545-4689-a418-eb7784613650@intel.com> From: Yosry Ahmed Date: Thu, 7 Mar 2024 15:37:04 -0800 Message-ID: Subject: Re: [RFC PATCH 1/3] x86/mm: fix LAM cr3 mask inconsistency during context switch To: Dave Hansen Cc: Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , "Kirill A. Shutemov" , x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: CC0A34000F X-Rspam-User: X-Stat-Signature: 3ipb7kcpkppz3r9wd64mfbrqug5n1b4e X-Rspamd-Server: rspam03 X-HE-Tag: 1709854660-819440 X-HE-Meta: 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 qp2Y1EYX TwntKMnGqywF4uC9Lzolzl3EfMHa7ueZdweZNf+mYtyvp7Vlg4uizZ4UZPpDQuvqAo4EXUiVhIVyV8jKftXCablBAjVlJAUcTIfb7IKG3sndTc3GMvjewRXREZZYEvMwD4kWDrwOa/7v6e7UdeV/Zfm25+eIKpMz4NRKD X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > Or we can avoid returning a value from the helper and avoid passing an > > mm. The callers would be more verbose, they'll have to call > > mm_lam_cr3_mask() and mm_untag_mask() and pass the results into the > > helper (set_tlbstate_lam_mode() or update_cpu_tlbstate_lam()). Another > > advantage of this is that we can move the READ_ONCE to > > switch_mm_irqs_off() and keep the comment here. > > > One thing I don't like about set_tlbstate_lam_mode() is that it's not > obvious that it's writing to "cpu_tlbstate" and its right smack in the > middle of a bunch of other writers to the same thing. > > But I'm also not sure that open-coding it at its three call sites makes > things better overall. > > I honestly don't have any brilliant suggestions. Let me ponder this a little bit and try to come up with something, I think a max of renaming and open-coding could make an improvement. Thanks!