From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF372C83F01 for ; Thu, 31 Aug 2023 12:51:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D64778D000E; Thu, 31 Aug 2023 08:51:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D13898D0001; Thu, 31 Aug 2023 08:51:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BDB228D000E; Thu, 31 Aug 2023 08:51:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id ACBD38D0001 for ; Thu, 31 Aug 2023 08:51:21 -0400 (EDT) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 878871C9691 for ; Thu, 31 Aug 2023 12:51:21 +0000 (UTC) X-FDA: 81184385562.05.8D37EDB Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf01.hostedemail.com (Postfix) with ESMTP id 805DA40004 for ; Thu, 31 Aug 2023 12:51:19 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=none; dmarc=none; spf=none (imf01.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1693486279; h=from:from:sender: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: in-reply-to:in-reply-to:references:references; bh=PzqccAgTnC2wqigtMsMGnsUlxawk3s1cXcT34hS2R14=; b=R1NExGrcNMG04LuU1UZEaz0+PRTLT+9pDYQIJACIZQPacFExLjrv195RW8MkcshLQ5nSYE oVe0pICpgkx+uac+hFtVDTHzhCvLIYyhO+plxwe2Zgq6VmRz0uFQWyZmj7IgEp8TeB5Zm/ AR7bYlNx+bZFv4PdvihD2rsRypI8R84= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=none; dmarc=none; spf=none (imf01.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1693486279; a=rsa-sha256; cv=none; b=1fp7aCURLf0MKbKsXAv+7c94ac0Sv5BS0z/sZ15GodnOGJZy+ybzqNnpoYMGa5udae5Y/n uTJ7NcJ//e5w859Ii8igTX6yNJKVazHYM1tCLSGihpETpERXJRkxK1lk8DfVn1stDFrTjY C8j0r6gcww2DgSEhGAD2KPuP/ETNn70= Received: by verein.lst.de (Postfix, from userid 2407) id C99B468C4E; Thu, 31 Aug 2023 14:51:10 +0200 (CEST) Date: Thu, 31 Aug 2023 14:51:09 +0200 From: Christoph Hellwig To: Jonathan Corbet Cc: Petr Tesarik , Stefano Stabellini , Russell King , Thomas Bogendoerfer , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , Greg Kroah-Hartman , "Rafael J. Wysocki" , Juergen Gross , Oleksandr Tyshchenko , Christoph Hellwig , Marek Szyprowski , Robin Murphy , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Petr Tesarik , Andy Shevchenko , Hans de Goede , James Seo , James Clark , Kees Cook , "moderated list:XEN HYPERVISOR ARM" , "moderated list:ARM PORT" , open list , "open list:MIPS" , "open list:XEN SWIOTLB SUBSYSTEM" , "open list:SLAB ALLOCATOR" , Roberto Sassu , petr@tesarici.cz Subject: Re: [PATCH v7 9/9] swiotlb: search the software IO TLB only if the device makes use of it Message-ID: <20230831125109.GA11562@lst.de> References: <87a5uz3ob8.fsf@meer.lwn.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87a5uz3ob8.fsf@meer.lwn.net> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspam-User: X-Stat-Signature: bzrkpzktrb3yatonnb4bto58mb6xjh8q X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 805DA40004 X-HE-Tag: 1693486279-724341 X-HE-Meta: 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 gZAUhIJu xpsshOLzudVlzX86UeUMzQ0LY40g213lXowPI03Xrwo3Bif3kmCmNZYtroklOZWsCRfKq4fQBjIY+nGOU+JEZPlvx9+BUEdP9raKIPFIMvgVshiE5j0nH6pEI+SHUdCPsqtrWCAlgyq2FGUac4gj9tnsM0g== 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: On Wed, Aug 09, 2023 at 03:20:43PM -0600, Jonathan Corbet wrote: > > spin_unlock_irqrestore(&dev->dma_io_tlb_lock, flags); > > > > - /* Pairs with smp_rmb() in swiotlb_find_pool(). */ > > - smp_wmb(); > > found: > > + dev->dma_uses_io_tlb = true; > > + /* Pairs with smp_rmb() in is_swiotlb_buffer() */ > > + smp_wmb(); > > + > > ...and here you set it if swiotlb is used. > > But, as far as I can tell, you don't actually *use* this field anywhere. > What am I missing? It's very much unused. Petr, I guess you wanted to use this in is_swiotlb_buffer to avoid the lookup unless required. Can you send a follow up?