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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 588E4C3A5A6 for ; Thu, 19 Sep 2019 15:17:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 27B5320665 for ; Thu, 19 Sep 2019 15:17:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403863AbfISPRo (ORCPT ); Thu, 19 Sep 2019 11:17:44 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:3260 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388706AbfISPRo (ORCPT ); Thu, 19 Sep 2019 11:17:44 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x8JFGHPk103875 for ; Thu, 19 Sep 2019 11:17:43 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2v4c390bjd-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 19 Sep 2019 11:17:42 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 19 Sep 2019 16:17:36 +0100 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x8JFHZAW52559994 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 19 Sep 2019 15:17:36 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B54C6A4055; Thu, 19 Sep 2019 15:17:35 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 638CFA4070; Thu, 19 Sep 2019 15:17:35 +0000 (GMT) Received: from pomme.tls.ibm.com (unknown [9.101.4.33]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 19 Sep 2019 15:17:35 +0000 (GMT) Subject: Re: [PATCH v2 2/2] powerpc/mm: call H_BLOCK_REMOVE when supported To: Michael Ellerman , benh@kernel.crashing.org, paulus@samba.org, aneesh.kumar@linux.ibm.com, npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20190916095543.17496-1-ldufour@linux.ibm.com> <20190916095543.17496-3-ldufour@linux.ibm.com> <87y2ylvhyo.fsf@mpe.ellerman.id.au> From: Laurent Dufour Date: Thu, 19 Sep 2019 17:17:35 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <87y2ylvhyo.fsf@mpe.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19091915-0012-0000-0000-0000034E1E3C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19091915-0013-0000-0000-00002188A0CF Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-09-19_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909190143 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 18/09/2019 à 15:42, Michael Ellerman a écrit : > Hi Laurent, > > Few comments ... Hi Michael, Thanks for the review and the nitpicking ;) > > Laurent Dufour writes: >> Now we do not call _BLOCK_REMOVE all the time when the feature is >> exhibited. > > This isn't true until after the patch is applied, ie. the tense is > wrong. The rest of the change log explains things fine, so just drop > that sentence I think. > > Can you include the info about the oops in here. > >> Depending on the hardware and the hypervisor, the hcall H_BLOCK_REMOVE may >> not be able to process all the page size for a segment base page size, as > ^ > sizes >> reported by the TLB Invalidate Characteristics.o > ^ > stray "o" >> >> For each couple base segment page size and actual page size, this > ^ > "pair of" >> characteristic is telling the size of the block the hcall is supporting. > ^ ^ > "tells us" supports >> >> Due to the involve complexity in do_block_remove() and call_block_remove(), > ^ > "required" is better I think >> and the fact currently a 8 size block is returned by the hypervisor, we > ^ ^ > that "block of size 8" >> are only supporting 8 size block to the H_BLOCK_REMOVE hcall. >> >> Furthermore a warning message is displayed at boot time in the case of an >> unsupported block size. > > I'm not sure we should be doing that? It could be unnecessarily spammy. > >> In order to identify this limitation easily in the code,a local define >> HBLKR_SUPPORTED_SIZE defining the currently supported block size, and a >> dedicated checking helper is_supported_hlbkr() are introduced. >> >> For regular pages and hugetlb, the assumption is made that the page size is >> equal to the base page size. For THP the page size is assumed to be 16M. >> >> Signed-off-by: Laurent Dufour >> --- >> arch/powerpc/platforms/pseries/lpar.c | 35 +++++++++++++++++++++++++-- >> 1 file changed, 33 insertions(+), 2 deletions(-) >> >> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c >> index 98a5c2ff9a0b..e2ad9b3b1097 100644 >> --- a/arch/powerpc/platforms/pseries/lpar.c >> +++ b/arch/powerpc/platforms/pseries/lpar.c >> @@ -65,6 +65,13 @@ EXPORT_SYMBOL(plpar_hcall_norets); >> */ >> static int hblkr_size[MMU_PAGE_COUNT][MMU_PAGE_COUNT]; >> >> +/* >> + * Due to the involved complexity, and that the current hypervisor is only >> + * returning this value or 0, we are limiting the support of the H_BLOCK_REMOVE >> + * buffer size to 8 size block. >> + */ >> +#define HBLKR_SUPPORTED_BLOCK_SIZE 8 >> + >> #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE >> static u8 dtl_mask = DTL_LOG_PREEMPT; >> #else >> @@ -993,6 +1000,15 @@ static void pSeries_lpar_hpte_invalidate(unsigned long slot, unsigned long vpn, >> #define HBLKR_CTRL_ERRNOTFOUND 0x8800000000000000UL >> #define HBLKR_CTRL_ERRBUSY 0xa000000000000000UL >> >> +/* >> + * Returned true if we are supporting this block size for the specified segment >> + * base page size and actual page size. >> + */ >> +static inline bool is_supported_hlbkr(int bpsize, int psize) >> +{ >> + return (hblkr_size[bpsize][psize] == HBLKR_SUPPORTED_BLOCK_SIZE); >> +} >> + >> /** >> * H_BLOCK_REMOVE caller. >> * @idx should point to the latest @param entry set with a PTEX. >> @@ -1152,7 +1168,11 @@ static inline void __pSeries_lpar_hugepage_invalidate(unsigned long *slot, >> if (lock_tlbie) >> spin_lock_irqsave(&pSeries_lpar_tlbie_lock, flags); >> >> - if (firmware_has_feature(FW_FEATURE_BLOCK_REMOVE)) >> + /* >> + * Assuming THP size is 16M, and we only support 8 bytes size buffer >> + * for the momment. >> + */ >> + if (is_supported_hlbkr(psize, MMU_PAGE_16M)) > > It's not very clear that this is correct in all cases. ie. how do we > know we're being called for THP and not regular huge page? > > I think we're only called via: > flush_hash_hugepage() > -> mmu_hash_ops.hugepage_invalidate() > pSeries_lpar_hugepage_invalidate() > -> __pSeries_lpar_hugepage_invalidate() > > And flush_hash_hugepage() is called via: > __hash_page_thp() > and > hpte_do_hugepage_flush() > > The first is presumably fine, the 2nd is called in a few places: > __flush_hash_table_range() under if (is_thp) > hash__pmd_hugepage_update() > > > But it's a little bit fragile if the code ever evolves. Not sure if > there's a better solution, other than just documenting it. Indeed __pSeries_lpar_hugepage_invalidate() can only be called for THP. flush_hash_hugepage() and hpte_do_hugepage_flush() are only defined (or valid) with CONFIG_TRANSPARENT_HUGEPAGE. As Aneesh remind me, "hugepage" stands for THP. > >> hugepage_block_invalidate(slot, vpn, count, psize, ssize); >> else >> hugepage_bulk_invalidate(slot, vpn, count, psize, ssize); >> @@ -1437,6 +1457,14 @@ void __init pseries_lpar_read_hblkr_characteristics(void) >> >> block_size = 1 << block_size; >> >> + /* >> + * If the block size is not supported by the kernel, report it, >> + * but continue reading the values, and the following blocks. >> + */ >> + if (block_size != HBLKR_SUPPORTED_BLOCK_SIZE) >> + pr_warn("Unsupported H_BLOCK_REMOVE block size : %d\n", >> + block_size); > > Does this need a printk? I'm worried it could end up triggering and > scaring people unnecessarily. I agree, will remove. > >> + >> for (npsize = local_buffer[idx++]; npsize > 0; npsize--) >> check_lp_set_hblk((unsigned int) local_buffer[idx++], >> block_size); >> @@ -1468,7 +1496,10 @@ static void pSeries_lpar_flush_hash_range(unsigned long number, int local) >> if (lock_tlbie) >> spin_lock_irqsave(&pSeries_lpar_tlbie_lock, flags); >> >> - if (firmware_has_feature(FW_FEATURE_BLOCK_REMOVE)) { >> + /* >> + * Currently, we only support 8 bytes size buffer in do_block_remove(). >> + */ >> + if (is_supported_hlbkr(batch->psize, batch->psize)) { >> do_block_remove(number, batch, param); >> goto out; >> } >> -- >> 2.23.0 > > cheers >