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=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,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 F022FC433ED for ; Sun, 25 Apr 2021 13:41:33 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 A548C6121D for ; Sun, 25 Apr 2021 13:41:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A548C6121D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.117164.223032 (Exim 4.92) (envelope-from ) id 1laf0X-0007FK-GG; Sun, 25 Apr 2021 13:41:09 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 117164.223032; Sun, 25 Apr 2021 13:41:09 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1laf0X-0007FD-DF; Sun, 25 Apr 2021 13:41:09 +0000 Received: by outflank-mailman (input) for mailman id 117164; Sun, 25 Apr 2021 13:41:08 +0000 Received: from mail.xenproject.org ([104.130.215.37]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1laf0W-0007F8-7t for xen-devel@lists.xenproject.org; Sun, 25 Apr 2021 13:41:08 +0000 Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1laf0U-0002EX-P1; Sun, 25 Apr 2021 13:41:06 +0000 Received: from 54-240-197-239.amazon.com ([54.240.197.239] helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1laf0U-0001ND-DA; Sun, 25 Apr 2021 13:41:06 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=jcseDq2ZdU1T0/rnFxbHc4SJN0BhJiMohi8QIY8/hu8=; b=PqcaPzFM5/uNcsvWa9hcWuVCV7 idWyZZkkQ8Z/b5vY/ipzo74swD6/Ke/cg+fgcAFGrmGIfWGKobhhre5/7CFZCeXnQrV3pl+4VoP+O Yv/XE1eSQVH3ygzTDhVSJg+d/fJhMtmGYp0xxnvLjj1iQ5ywq+7XElFmggFluiXFASSA=; Subject: Re: [PATCH] xen/page_alloc: Remove dead code in alloc_domheap_pages() To: Jan Beulich Cc: Julien Grall , Andrew Cooper , George Dunlap , Ian Jackson , Stefano Stabellini , Wei Liu , xen-devel@lists.xenproject.org References: <20210406192246.15657-1-julien@xen.org> <6d3593cb-40d4-df17-4070-a6c18ea7d62b@suse.com> From: Julien Grall Message-ID: <6b37dc84-a251-a9d7-071d-65d2afad6361@xen.org> Date: Sun, 25 Apr 2021 14:41:04 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <6d3593cb-40d4-df17-4070-a6c18ea7d62b@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Hi Jan, On 07/04/2021 10:25, Jan Beulich wrote: > On 06.04.2021 21:22, Julien Grall wrote: >> --- a/xen/common/page_alloc.c >> +++ b/xen/common/page_alloc.c >> @@ -457,6 +457,12 @@ static long total_avail_pages; >> static DEFINE_SPINLOCK(heap_lock); >> static long outstanding_claims; /* total outstanding claims by all domains */ >> >> +static void __init __maybe_unused build_assertions(void) >> +{ >> + /* Zone 0 is reserved for Xen, so we at least need two zones to function.*/ >> + BUILD_BUG_ON(NR_ZONES < 2); >> +} > > With a couple of transformations this could also be > > BUILD_BUG_ON(PADDR_BITS <= PAGE_SHIFT); > > i.e. you're checking that the architecture allows for at least two > pages to be addressable. Is this really a useful thing to check? I saw it, but I was concerned that someone may modify the definition of NR_ZONES without looking at the rest of the code base. Anyway, I guess that the ASSERT(zone_hi != 0) in the code should be sufficient to catch such problem. So I will drop it. > > Irrespective of the usefulness, if this is to be kept I think the > function wants to live at the end of the source file, like the > majority of other files have it (another consistent place could > be at the top of the file, after all #include-s, as can be found > in two other cases). > >> @@ -2340,8 +2346,9 @@ struct page_info *alloc_domheap_pages( >> >> bits = domain_clamp_alloc_bitsize(memflags & MEMF_no_owner ? NULL : d, >> bits ? : (BITS_PER_LONG+PAGE_SHIFT)); >> - if ( (zone_hi = min_t(unsigned int, bits_to_zone(bits), zone_hi)) == 0 ) >> - return NULL; >> + >> + zone_hi = min_t(unsigned int, bits_to_zone(bits), zone_hi); >> + ASSERT(zone_hi != 0); > > With the function above preferably dropped or at least moved, > Reviewed-by: Jan Beulich > > I'd like to point out though that I think this would be a good > opportunity to eliminate the use of min_t() here, by changing > bits_to_zone()'s 1 to 1u. But I suppose you again would prefer > to not make this extra change right here, despite it being > somewhat related to bits_to_zone() only ever returning positive > values. In general, I am in not in favor to modify unrelated to code (e.g. coding style) or things that deserved a more than a one-line explanation in the commit message. This is not the case here, so I will respin it and switch from min_t to min. Cheers, -- Julien Grall