From nobody Tue May 13 15:17:08 2025 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D6369204875; Tue, 1 Apr 2025 20:53:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743540808; cv=none; b=pN3q10Okotvme0VaFIdRsCN4kPTyG1q41ITZLWHDOMeAZXAcqe1PYWW969GZSzezCpoi6ZQrFzOtUsBU7VxrZYQQndm8yDuuAUPvUY0rclFLYU63JX+7NKA5wkOLj1mXfnFvyk/JIr3qq2b05kNlMX1al8GucP8JhXT+jo9H59M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743540808; c=relaxed/simple; bh=rezkbcoOFKwTz7C5NqmHCDUWOf4SRkyuFzLRBTFOe6s=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=EBGps19eXfoXByTOVOhcpgMSsADa8UzUKGLjUV7xY91JVeAZ6n1hJt0KiOyyzYlazqvm20pacQSPOcL0cRUklVpJehfQtCfQWInUBMuRlQu+XwQnYNnyPZ1uJ5rADcymkpnCly5wiS6iW82lYez46f84R51+GIhMGA4i2l1I4pc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=oZ3VY7jH; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=wjYez3Yh; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="oZ3VY7jH"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="wjYez3Yh" Date: Tue, 01 Apr 2025 20:53:21 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1743540802; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bbyYn80ysDKfOOOUjXfZJIarNJI5LVfzzo9T/D0gY9k=; b=oZ3VY7jHlzLSikDR1jV9je6T+X3ysta8EaGsu2EMYEE5oIxWSGt9I0N+8wZmiYmJOE03Fs ROlUpkoHov9TOVlgOM0PNFFMYOg44PBqKtBXzKGiG4ifdlFq3g1EehMgYWxXFiB0G84CsJ Yl5+EQyHYP/TeBR+CpyIYNSn5aEsbIFE3VspMnGYF41EMk8Ts9QIddNTmHtFDVRGwHnShJ 0dwksgnwJODiBSU3L+6zAs4HKxDWeAt3E4TxldWlMx1jj2jYKP2gOurqg2VAN1gwV9qEua P46ac8IuI0yLz+Th8dTr7TvOT+zStBHSFEk5pwFB4iYZ19YulmNRRrO0+mj1xw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1743540802; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bbyYn80ysDKfOOOUjXfZJIarNJI5LVfzzo9T/D0gY9k=; b=wjYez3Yhz6bDhiEDkPtYo2zt2cRHNGuM5b9zq30OcbQ33pUyr5mfZcSnimBLa9G99dnU4D Lx4CNjKmXe/JNYCw== From: "tip-bot2 for Mateusz Guzik" <tip-bot2@linutronix.de> Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/mm] x86/mm: Stop prefetching current->mm->mmap_lock on page faults Cc: Mateusz Guzik <mjguzik@gmail.com>, Ingo Molnar <mingo@kernel.org>, Andy Lutomirski <luto@kernel.org>, Peter Zijlstra <peterz@infradead.org>, Rik van Riel <riel@surriel.com>, "H. Peter Anvin" <hpa@zytor.com>, Linus Torvalds <torvalds@linux-foundation.org>, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250401143520.1113572-1-mjguzik@gmail.com> References: <20250401143520.1113572-1-mjguzik@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: <linux-kernel.vger.kernel.org> List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org> List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org> MIME-Version: 1.0 Message-ID: <174354080164.14745.16617051817056445612.tip-bot2@tip-bot2> Robot-ID: <tip-bot2@linutronix.de> Robot-Unsubscribe: Contact <mailto:tglx@linutronix.de> to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable The following commit has been merged into the x86/mm branch of tip: Commit-ID: 0b2695d58e800ad53e718d003310829db492a39c Gitweb: https://git.kernel.org/tip/0b2695d58e800ad53e718d003310829db= 492a39c Author: Mateusz Guzik <mjguzik@gmail.com> AuthorDate: Tue, 01 Apr 2025 16:35:20 +02:00 Committer: Ingo Molnar <mingo@kernel.org> CommitterDate: Tue, 01 Apr 2025 22:47:02 +02:00 x86/mm: Stop prefetching current->mm->mmap_lock on page faults The prefetchw() dates back decades and the fundamental notion of doing something like this on a lock is shady. Moreover, for a few years now in the fast path faults are handled with RCU + per-vma locking, hopefully not even looking at the lock to begin with. As such just remove it. I did not see a point benchmarking this. Given that it is not expected to be looked at by default justifies not doing the prefetch. Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@surriel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20250401143520.1113572-1-mjguzik@gmail.com --- arch/x86/mm/fault.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 296d294..697432f 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -13,7 +13,6 @@ #include <linux/mmiotrace.h> /* kmmio_handler, ... */ #include <linux/perf_event.h> /* perf_sw_event */ #include <linux/hugetlb.h> /* hstate_index_to_shift */ -#include <linux/prefetch.h> /* prefetchw */ #include <linux/context_tracking.h> /* exception_enter(), ... */ #include <linux/uaccess.h> /* faulthandler_disabled() */ #include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/ @@ -1496,8 +1495,6 @@ DEFINE_IDTENTRY_RAW_ERRORCODE(exc_page_fault) =20 address =3D cpu_feature_enabled(X86_FEATURE_FRED) ? fred_event_data(regs)= : read_cr2(); =20 - prefetchw(¤t->mm->mmap_lock); - /* * KVM uses #PF vector to deliver 'page not present' events to guests * (asynchronous page fault mechanism). The event happens when a