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 E993B1553AB; Thu, 21 Nov 2024 15:30:19 +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=1732203021; cv=none; b=oOrVJU6a/UqtsxndvDzmHU8e63LW/zWUbW7ZIKVf47v5wOM7b78uR5QA4C9dvxr7oo5HrZG/rE7AGLDE1QPGSwpf+68nApjnMAc6gnxB50sTtRzrTqhcLXgxFe9okfO6d9iQMG1nNuBpO27WfMykQuQFAwH7UMfhxrFW/YyWU4A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732203021; c=relaxed/simple; bh=t1OS0SZ4JnSMKv7XRJ70eysyTs6yIg/uNEDpFJowCak=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bUqcPhvNphSBgYEGneiMuI/oqQ0xehM2cq7QsoMybNcAAG1XMxGkht/LQSL2m8XtwRnF016jnc8ZtAtJSFt30OE70mYUaYTOqZjlGfgYnePRLxe2euJzc+YyVb8z9Fb+49orh9r07sErPgpKsVsRni2fIPszjTWFemzEzorgLEY= 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=jtbwyGXC; 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="jtbwyGXC" 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=idhvmbSpjgyt1zH7fW+NeMIym2Pxx0s6Zv4Z+MCkqpE=; b=jtbwyGXCj+fwhrEMqG86bsZNay X+Nhdx5L2GrnjsPVKZMH/9Xlth2dXn7V1q8B2uGnwZSnS6VwBnDlo5l2mF+gNGa53bifeHhjLxjzg LuuxbLivsvnoJwHFWwJ9HtpsFFWT8w0DB1+4DsJiSAIW+c3l+jOZYuC50VHY94USWDg0cH0Q7S79T 1ZsOjEJHR7cDhHo4Vg+1JyCeUwWbUtSCdu8Z1iaCD/rwUxfrFtSe4/gPhcmFLw431+Dp/q/9biI53 QSscxd44bVnld3NBcnhmjIxaeXKZ8sAp+fCs+CkEKohDWDGM4zASCp/XotZ1Hh/spjqUWQHzjx5dH aH1ns5Yg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tE98L-00000000av5-0FLU; Thu, 21 Nov 2024 15:30:17 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 3DCD6300848; Thu, 21 Nov 2024 16:30:16 +0100 (CET) Date: Thu, 21 Nov 2024 16:30:16 +0100 From: Peter Zijlstra To: Dave Hansen Cc: Valentin Schneider , 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 , Petr Tesarik Subject: Re: [RFC PATCH v3 13/15] context_tracking,x86: Add infrastructure to defer kernel TLBI Message-ID: <20241121153016.GL39245@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> Precedence: bulk X-Mailing-List: linux-doc@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: <4b562cd0-7500-4b3a-8f5c-e6acfea2896e@intel.com> On Thu, Nov 21, 2024 at 07:07:44AM -0800, Dave Hansen wrote: > On 11/21/24 03:12, Peter Zijlstra wrote: > >> I see e.g. ds_clear_cea() clears PTEs that can have the _PAGE_GLOBAL flag, > >> and it correctly uses the non-deferrable flush_tlb_kernel_range(). > > > > I always forget what we use global pages for, dhansen might know, but > > let me try and have a look. > > > > I *think* we only have GLOBAL on kernel text, and that only sometimes. > > I think you're remembering how _PAGE_GLOBAL gets used when KPTI is in play. Yah, I suppose I am. That was the last time I had a good look at this stuff :-) > Ignoring KPTI for a sec... We use _PAGE_GLOBAL for all kernel mappings. > Before PCIDs, global mappings let the kernel TLB entries live across CR3 > writes. When PCIDs are in play, global mappings let two different ASIDs > share TLB entries. Hurmph.. bah. That means we do need that horrible CR4 dance :/