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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 8D01AC4360C for ; Wed, 9 Oct 2019 01:11:56 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 64732206C2 for ; Wed, 9 Oct 2019 01:11:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 64732206C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:38414 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iI0WB-0003S0-JS for qemu-devel@archiver.kernel.org; Tue, 08 Oct 2019 21:11:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40295) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iI0VS-0002zq-6n for qemu-devel@nongnu.org; Tue, 08 Oct 2019 21:11:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iI0VQ-0002Nj-SY for qemu-devel@nongnu.org; Tue, 08 Oct 2019 21:11:10 -0400 Received: from mga18.intel.com ([134.134.136.126]:21434) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iI0VQ-0002MD-JO for qemu-devel@nongnu.org; Tue, 08 Oct 2019 21:11:08 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 Oct 2019 18:11:06 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,273,1566889200"; d="scan'208";a="345209452" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga004.jf.intel.com with ESMTP; 08 Oct 2019 18:11:05 -0700 Date: Wed, 9 Oct 2019 09:10:48 +0800 From: Wei Yang To: "Dr. David Alan Gilbert" Subject: Re: [PATCH 2/2] migration/postcopy: map large zero page in postcopy_ram_incoming_setup() Message-ID: <20191009011048.GD26203@richard> References: <20191005135021.21721-1-richardw.yang@linux.intel.com> <20191005135021.21721-3-richardw.yang@linux.intel.com> <20191008172423.GH3441@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191008172423.GH3441@work-vm> User-Agent: Mutt/1.9.4 (2018-02-28) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 134.134.136.126 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Wei Yang Cc: qemu-devel@nongnu.org, Wei Yang , quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Oct 08, 2019 at 06:24:23PM +0100, Dr. David Alan Gilbert wrote: >* Wei Yang (richardw.yang@linux.intel.com) wrote: >> postcopy_ram_incoming_setup() and postcopy_ram_incoming_cleanup() are >> counterpart. It is reasonable to map/unmap large zero page in these two >> functions respectively. >> >> Signed-off-by: Wei Yang > >Yes, OK. > >> --- >> migration/postcopy-ram.c | 34 +++++++++++++++++----------------- >> 1 file changed, 17 insertions(+), 17 deletions(-) >> >> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c >> index e554f93eec..813cfa5c42 100644 >> --- a/migration/postcopy-ram.c >> +++ b/migration/postcopy-ram.c >> @@ -1142,6 +1142,22 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis) >> return -1; >> } >> >> + /* >> + * Map large zero page when kernel can't use UFFDIO_ZEROPAGE for hugepages >> + */ >> + mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size, >> + PROT_READ | PROT_WRITE, >> + MAP_PRIVATE | MAP_ANONYMOUS, >> + -1, 0); >> + if (mis->postcopy_tmp_zero_page == MAP_FAILED) { >> + int e = errno; >> + mis->postcopy_tmp_zero_page = NULL; >> + error_report("%s: Failed to map large zero page %s", >> + __func__, strerror(e)); >> + return -e; > >Note this starts returning -errno where the rest of this function >returns 0 or -1; returning -errno is a good thing I think and it might >be good to change the other returns. > This is reasonable, while I am thinking how caller would handle this. For example, the return value would be finally returned to qemu_loadvm_state_main(). If we handle each errno respectively in this function, the code would be difficult to read and maintain. Would it be good to classify return value to different category? Like POSTCOPY_FATAL POSTCOPY_RETRY POSTCOPY_DISABLE > >Reviewed-by: Dr. David Alan Gilbert > >> + } >> + memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size); >> + >> /* >> * Ballooning can mark pages as absent while we're postcopying >> * that would cause false userfaults. >> @@ -1248,23 +1264,7 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, >> qemu_ram_block_host_offset(rb, >> host)); >> } else { >> - /* The kernel can't use UFFDIO_ZEROPAGE for hugepages */ >> - if (!mis->postcopy_tmp_zero_page) { >> - mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size, >> - PROT_READ | PROT_WRITE, >> - MAP_PRIVATE | MAP_ANONYMOUS, >> - -1, 0); >> - if (mis->postcopy_tmp_zero_page == MAP_FAILED) { >> - int e = errno; >> - mis->postcopy_tmp_zero_page = NULL; >> - error_report("%s: %s mapping large zero page", >> - __func__, strerror(e)); >> - return -e; >> - } >> - memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size); >> - } >> - return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, >> - rb); >> + return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page, rb); >> } >> } >> >> -- >> 2.17.1 >> >-- >Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK -- Wei Yang Help you, Help me