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 X-Spam-Level: X-Spam-Status: No, score=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC137C282DA for ; Wed, 17 Apr 2019 23:21:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A1DA217FA for ; Wed, 17 Apr 2019 23:21:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387695AbfDQXVG (ORCPT ); Wed, 17 Apr 2019 19:21:06 -0400 Received: from belmont80srvr.owm.bell.net ([184.150.200.80]:44676 "EHLO mtlfep02.bell.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2387630AbfDQXVF (ORCPT ); Wed, 17 Apr 2019 19:21:05 -0400 Received: from bell.net mtlfep02 184.150.200.30 by mtlfep02.bell.net with ESMTP id <20190417232104.JXFW4444.mtlfep02.bell.net@mtlspm01.bell.net> for ; Wed, 17 Apr 2019 19:21:04 -0400 Received: from [192.168.2.49] (really [70.53.52.226]) by mtlspm01.bell.net with ESMTP id <20190417232104.KIVB87666.mtlspm01.bell.net@[192.168.2.49]>; Wed, 17 Apr 2019 19:21:04 -0400 Subject: Re: [PATCH] parisc: Remove lock code to serialize TLB operations in pacache.S From: John David Anglin To: Helge Deller , Sven Schnelle Cc: linux-parisc , James Bottomley References: <20190417205515.GA2001@t470p.stackframe.org> <19e13735-bfe6-531a-1920-d8955546040e@gmx.de> <28d40070-75b9-a5c3-94ab-544345723cd9@bell.net> Openpgp: preference=signencrypt Message-ID: Date: Wed, 17 Apr 2019 19:21:00 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <28d40070-75b9-a5c3-94ab-544345723cd9@bell.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-CM-Analysis: v=2.3 cv=ZMOpZkzb c=1 sm=1 tr=0 cx=a_idp_x a=eekNWfHKKKZHbRJeTMr8Cw==:117 a=eekNWfHKKKZHbRJeTMr8Cw==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=IkcTkHD0fZMA:10 a=oexKYjalfGEA:10 a=FBHGMhGWAAAA:8 a=VwQbUJbxAAAA:8 a=zh-XebEQfMItxhbe-O0A:9 a=QEXdDO2ut3YA:10 a=9gvnlMMaQFpL9xblJ6ne:22 a=AjGcO6oz07-iQ99wixmX:22 X-CM-Envelope: MS4wfMffUtOEgwaKcCH3IEwPGyMOY/nWxkNlowokknJ7/zRgLRC1KM+rU9AX9itgDccdm5s4GZzD4YN7V97fMkwynUoLmtlr+bQCCI9WGScYmx/WFMC4Hh6C bn2cL5g1u7jYSsZ5t0JntDPTU+h6w9sJH0TUD0sLfzrf5cSVCBqKVZ9ug/3nKDNjuswJF1V2NldpQQ== Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On 2019-04-17 5:09 p.m., John David Anglin wrote: > On 2019-04-17 5:01 p.m., Helge Deller wrote: >> On 17.04.19 22:58, Helge Deller wrote: >>> On 17.04.19 22:55, Sven Schnelle wrote: >>>> On Fri, Apr 12, 2019 at 07:12:04PM -0400, John David Anglin wrote: >>>>> TLB operations only need to be serialized on machines with the Merced (Stretch) bus. >>>>> The only machines in this category are L and N class, and they require a 64-bit PA 2.0 >>>>> kernel. On these machines, we use local TLB purges in the tmpalias routines. We don't >>>>> need to serialize TLB purges on all other machines. Thus, the lock/unlock code can be >>>>> removed when CONFIG_PA20 is not defined. Further, when CONFIG_PA20 is not defined, >>>>> alternative patching converts the TLB purges to local purges when PA 2.0 hardware has >>>>> been detected. >>>>> >>>>> Signed-off-by: John David Anglin >>>> I had this patch running on my C8000 and J5000 for a few days, and haven't >>>> encountered any issues. >>> Nah... >>> I do have one of the critical machines (rp5470), and I tried >>> to add the necessary code to detect and handle the TLB serialization. >>> Until now the patch sadly doesn't work yet (hangs at boot), it still needs more work. >>> You can find it in my git tree: >>> https://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux.git/commit/?h=tlb-flush-merced-bus&id=fc6044f83cb9828ec6ebecb23a46549d9ebc518f >> Please ignore my comments. >> Dave's patch is OK. >> >> I mixed it up with the Mikulas Patocka's patch: "use per-pagetable spinlock" >> https://patchwork.kernel.org/patch/10888249/ > I think this hunk needs fixing to handle merced case: > > diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S > index 5796524a3137..3e11fdd9d3af 100644 > --- a/arch/parisc/kernel/entry.S > +++ b/arch/parisc/kernel/entry.S > @@ -48,14 +48,9 @@ >      .level 2.0 >  #endif >   > -    .import        pa_tlb_lock,data > -    .macro  load_pa_tlb_lock reg > -#if __PA_LDCW_ALIGNMENT > 4 > -    load32    PA(pa_tlb_lock) + __PA_LDCW_ALIGNMENT-1, \reg > -    depi    0,31,__PA_LDCW_ALIGN_ORDER, \reg > -#else > -    load32    PA(pa_tlb_lock), \reg > -#endif > +    .macro  load_process_pte_lock reg > +    mfctl        %cr25,\reg > +    addil        L%((PAGE_SIZE << PGD_ALLOC_ORDER) - PAGE_SIZE),\reg >      .endm >   >      /* space_to_prot macro creates a prot id from a space id */ Another option might be to remove pa_serialize_tlb_flushes here: +    if (unlikely(pgd == swapper_pg_dir) || pa_serialize_tlb_flushes) +        return &pa_tlb_flush_lock; This might be the better solution.  You have serialized the TLB purges using the pa_tlb_flush_lock. Dave -- John David Anglin dave.anglin@bell.net