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charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 18B9E14000E X-Rspamd-Server: rspam12 X-Stat-Signature: 94ttmff6htwk1poz5fei4moxjbb6bws1 X-Rspam-User: X-HE-Tag: 1735847743-720220 X-HE-Meta: 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 2ku0S0GW LGdichKUwJn0AWvqwX/KHa5dWc3NFs5ReSpo7bGa+U8BuuQkvgBEp08x9/bVAkf64ENqKPtZ496JGW+k2uddYpqb6iT02niTIAgPgjCTkuZtFw7PBfIHuEw86Yd/FcsEcxCJvBzmEJpopD3NOc2E4IvHNI7+JGf5ExZIJECxq1GGfmvxcK+EqAo8ttDc/pkYb8bcyhn7NfGXh8uAn6oCsNzEwriLIG25GBU20/wjl1dXxErYJh3YDS0AIbN6NEjX/vaSWSNdq1GtOsoKYhGGyC+zR1PK3kTN6+C9HvOU1BHY0D7CLkN+Kre7xRcJHPikqWmYv8C/yCFAjHfXQnUiXW3uxAQ== 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 Tue, Dec 31, 2024 at 11:11:51AM -0500, Rik van Riel wrote: > On Mon, 2024-12-30 at 19:41 +0100, Borislav Petkov wrote: > > 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. > > That would be a question for Peter :) Well, I've already answered why we need this in the previous thread but it wasn't preserved :-( Currently GUP-fast serializes against table-free by disabling interrupts, which in turn holds of the TLBI-IPIs. Since you're going to be doing broadcast TLBI -- without IPIs, this no longer works and we need other means of serializing GUP-fast vs table-free. MMU_GATHER_RCU_TABLE_FREE is that means. So where previously paravirt implementations of tlb_flush_multi might require this (because of virt optimizations that avoided the TLBI-IPI), this broadcast invalidate now very much requires this for native.