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Received: from 77-249-17-89.cable.dynamic.v4.ziggo.nl ([77.249.17.89] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tQ9cB-000000044bO-0pOW; Tue, 24 Dec 2024 18:26:43 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 0A721300478; Tue, 24 Dec 2024 19:26:43 +0100 (CET) Date: Tue, 24 Dec 2024 19:26:42 +0100 From: Peter Zijlstra 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, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH 01/11] x86/mm: make MMU_GATHER_RCU_TABLE_FREE unconditional Message-ID: <20241224182642.GC17252@noisy.programming.kicks-ass.net> References: <20241223025751.3268975-1-riel@surriel.com> <20241223025751.3268975-2-riel@surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241223025751.3268975-2-riel@surriel.com> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4AF2640008 X-Stat-Signature: od4o3qfn1c7et17zcwijup13mj8fop5o X-Rspam-User: X-HE-Tag: 1735064741-323256 X-HE-Meta: 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 f0DqqzkW RUTfYdN4WAa22m9NjMKLKY9ZiSecY+IjmN6XrQpHmfDAlyVLbGuXskGJ7adLsOq001wZf5gey6uecpRehHxbsXTlKZhgolm/+59wmgYrSL7a/6nlx44bNx4xnWWUzVc6QSA35V5uUJGEbDbyGTRXLEG9CjKFDABxc1z+gYeQSJu1/xF9YageukwBo8y1OIN8NMH2Q91d9zQK5aFTa6ipu3r8+Dt1UBC5y7H5XAr4CwdTmIrPN0bat+FJNElDdCd6UYUOVid6gUVhxSRolBI/p7QOL3FDmI7ipypkXJO1Y8J2CW0W9B3wWWahiMh6r+TcJY4FvtP3XZMz4/y2BiBPuM3mH69+Sqg47yi8a+pRKii0X/y0= 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 Sun, Dec 22, 2024 at 09:55:07PM -0500, Rik van Riel wrote: > Currently x86 usse 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. More importantly, the changes you're proposing very much rely on this. Without TLBi IPIs nothing serializes GUP-fast vs TLBi and this RCU-ish table free scheme is required. > Signed-off-by: Rik van Riel > Suggested-by: Peter Zijlstra > --- > arch/x86/Kconfig | 2 +- > arch/x86/kernel/paravirt.c | 7 +------ > 2 files changed, 2 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 9d7bd0ae48c4..e8743f8c9fd0 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -274,7 +274,7 @@ config X86 > select HAVE_PCI > select HAVE_PERF_REGS > select HAVE_PERF_USER_STACK_DUMP > - select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT > + select MMU_GATHER_RCU_TABLE_FREE > select MMU_GATHER_MERGE_VMAS > select HAVE_POSIX_CPU_TIMERS_TASK_WORK > select HAVE_REGS_AND_STACK_ACCESS_API > diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c > index fec381533555..2b78a6b466ed 100644 > --- a/arch/x86/kernel/paravirt.c > +++ b/arch/x86/kernel/paravirt.c > @@ -59,11 +59,6 @@ void __init native_pv_lock_init(void) > static_branch_enable(&virt_spin_lock_key); > } > > -static void native_tlb_remove_table(struct mmu_gather *tlb, void *table) > -{ > - tlb_remove_page(tlb, table); > -} > - > struct static_key paravirt_steal_enabled; > struct static_key paravirt_steal_rq_enabled; > > @@ -191,7 +186,7 @@ struct paravirt_patch_template pv_ops = { > .mmu.flush_tlb_kernel = native_flush_tlb_global, > .mmu.flush_tlb_one_user = native_flush_tlb_one_user, > .mmu.flush_tlb_multi = native_flush_tlb_multi, > - .mmu.tlb_remove_table = native_tlb_remove_table, > + .mmu.tlb_remove_table = tlb_remove_table, > > .mmu.exit_mmap = paravirt_nop, > .mmu.notify_page_enc_status_changed = paravirt_nop, > -- > 2.47.1 >