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Mon, 30 Dec 2024 18:41:24 +0000 (UTC) Date: Mon, 30 Dec 2024 19:41:18 +0100 From: Borislav Petkov To: Rik van Riel Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, akpm@linux-foundation.org, nadav.amit@gmail.com, zhengqi.arch@bytedance.com, linux-mm@kvack.org Subject: Re: [PATCH 01/12] x86/mm: make MMU_GATHER_RCU_TABLE_FREE unconditional Message-ID: <20241230184118.GMZ3LpTn3dHvu_bq-p@fat_crate.local> References: <20241230175550.4046587-1-riel@surriel.com> <20241230175550.4046587-2-riel@surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241230175550.4046587-2-riel@surriel.com> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8E0D2140014 X-Stat-Signature: hk698ofbzyk56pfpi1ienssj9mro4wit X-Rspam-User: X-HE-Tag: 1735584073-994719 X-HE-Meta: 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 riVf3m1i WhYq5vyFCeghKIxixYsa39Hr7s2WH/jv5zDj1USGNuc+ORjJmlg1ldJdfLWhZle2jtqHsoxatdR+J6rVFgalSyP6rTq8C7zg8Wmt26uzylzWt0r2Fx9nFoqYtWxmK3k5osVC0zjOsPX8JT7MT7ZXuDvkqx5vSLzg5aOvKr5ZsT4FdJhWUZQ97hCL22unofKdGr1CLeLyyJTbqe+TgVW7uvoJXGBZR2//bX4IIfFCZ4TwySC7njC8mg1SLmOyavDoiVAroBIiQnEDEuMwQw9QL7GbIuVV22i2J99OIdnAg2rwF3aO5AVX5R3VVmfpdgRhUhEhr/rIDgnKf1E1YLzkLedKrwQ== 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: List-Subscribe: List-Unsubscribe: On Mon, Dec 30, 2024 at 12:53:02PM -0500, Rik van Riel wrote: > Currently x86 uses CONFIG_MMU_GATHER_TABLE_FREE when using > paravirt, and not when running on bare metal. > > There is no real good reason to do things differently for > each setup. Make them all the same. > > After this change, the synchronization between get_user_pages_fast > and page table freeing is handled by RCU, which prevents page tables > from being reused for other data while get_user_pages_fast is walking > them. I'd rather like to read here why this is not a problem anymore and why 48a8b97cfd80 ("x86/mm: Only use tlb_remove_table() for paravirt") is not relevant anymore. > This allows us to invalidate page tables while other CPUs have ^^ Please use passive voice in your commit message: no "we" or "I", etc, and describe your changes in imperative mood. Personal pronouns are ambiguous in text, especially with so many parties/companies/etc developing the kernel so let's avoid them please. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette