From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 9A6F02236FA; Mon, 9 Dec 2024 12:12:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733746375; cv=none; b=A9xrwAUxvI95FnlHAmcInFMJvR5Oeg+6drRyaHoVX36r1vR6TGMhXTavmyj9L2oj9JD9l+dIsg9k1dFC1sATZOQFe1h3VS44gSNh5buDxztTvhpvee/gWuaJ2hFnP4MXsj0erhUdCviYT94Q060vE4VONWkTUePwKnF2vVl4z3k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733746375; c=relaxed/simple; bh=VmJgxY8JyHe4LPcKfR3zGqif4VDPc4khkHgSpIUKuLQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=h0RnniCFnX+VM2XmA8/PXlFNXrBH+lVe6nYIMeyZX5SufKK/V8gb2OZ3Y05MiL7h/EvIFm+nPkGYpdfF6QOWVzoDA7BiW+6U98B5BAzs5iRAlPB8vsguQMF3temQLYZ+BkcmHC0+2iFXH/4eCQgMNgP7rgURLkRtgOsFLCYB7GA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=KDB6uYED; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="KDB6uYED" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=uVT5Gi2KQmMoQpuKPHzUhOIG+qt0YGmH2vT/S1/cY9s=; b=KDB6uYEDfLPVKzKPUOzo8eD3z6 oLNbK1X3DwOjgnTiEsJ930xFhE1kUwiAEEcdqt5KaAZ4d7H45sMOZ72GVD2kljqEiOxunf3ZeaHBA oKPYPvUg3/H8lMDYDTwXM6Rjzo3HpJjJ0LrgUUuVQB8k2p0qQeVolxYqooGEDzVuPKTWy3wi+Y+e8 zGvxiKlH+29kd/OONbtvefEtZpw66LBUJXc18/7GTsMi18v14Ast8dL4bsGmw+GEOO4agRu7V+tPi zhPLoXmG2VJvw23vIYnpHN0wraWDrv/HsDqCWDieYP8tz+T1YhZLA2DBIJbu9ICkjU56I2dedVPx/ TnlD5zcA==; Received: from 77-249-17-89.cable.dynamic.v4.ziggo.nl ([77.249.17.89] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tKcd8-00000003X9M-3OPg; Mon, 09 Dec 2024 12:12:51 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 6352330040C; Mon, 9 Dec 2024 13:12:49 +0100 (CET) Date: Mon, 9 Dec 2024 13:12:49 +0100 From: Peter Zijlstra To: Valentin Schneider Cc: Petr Tesarik , Dave Hansen , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, x86@kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org, Steven Rostedt , Masami Hiramatsu , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Andy Lutomirski , Frederic Weisbecker , "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Josh Poimboeuf , Jason Baron , Kees Cook , Sami Tolvanen , Ard Biesheuvel , Nicholas Piggin , Juerg Haefliger , Nicolas Saenz Julienne , "Kirill A. Shutemov" , Nadav Amit , Dan Carpenter , Chuang Wang , Yang Jihong , Petr Mladek , "Jason A. Donenfeld" , Song Liu , Julian Pidancet , Tom Lendacky , Dionna Glaze , Thomas =?iso-8859-1?Q?Wei=DFschuh?= , Juri Lelli , Marcelo Tosatti , Yair Podemsky , Daniel Wagner Subject: Re: [RFC PATCH v3 13/15] context_tracking,x86: Add infrastructure to defer kernel TLBI Message-ID: <20241209121249.GN35539@noisy.programming.kicks-ass.net> References: <20241119153502.41361-1-vschneid@redhat.com> <20241119153502.41361-14-vschneid@redhat.com> <20241120152216.GM19989@noisy.programming.kicks-ass.net> <20241120153221.GM38972@noisy.programming.kicks-ass.net> <20241121111221.GE24774@noisy.programming.kicks-ass.net> <4b562cd0-7500-4b3a-8f5c-e6acfea2896e@intel.com> <20241121153016.GL39245@noisy.programming.kicks-ass.net> <20241205183111.12dc16b3@mordecai.tesarici.cz> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Dec 09, 2024 at 01:04:43PM +0100, Valentin Schneider wrote: > > But I wonder what exactly was the original scenario encountered by > > Valentin. I mean, if TLB entry invalidations were necessary to sync > > changes to kernel text after flipping a static branch, then it might be > > less overhead to make a list of affected pages and call INVLPG on them. No; TLB is not involved with text patching (on x86). > > Valentin, do you happen to know? > > So from my experimentation (hackbench + kernel compilation on housekeeping > CPUs, dummy while(1) userspace loop on isolated CPUs), the TLB flushes only > occurred from vunmap() - mainly from all the hackbench threads coming and > going. Right, we have virtually mapped stacks.