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=-5.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 B284EC2D0A8 for ; Mon, 28 Sep 2020 09:10:17 +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 3437121D7F for ; Mon, 28 Sep 2020 09:10:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=suse.com header.i=@suse.com header.b="VNer4sy8" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3437121D7F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kMpAT-0001Ut-Jn; Mon, 28 Sep 2020 09:09:57 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kMpAS-0001Uj-1J for xen-devel@lists.xenproject.org; Mon, 28 Sep 2020 09:09:56 +0000 X-Inumbo-ID: 4d0f63f6-da91-4922-bd50-49bcae10d705 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 4d0f63f6-da91-4922-bd50-49bcae10d705; Mon, 28 Sep 2020 09:09:55 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1601284194; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YmwCKo/pnbI+klT4n6rPfcFqGQ0z4n1gJyTc1Je6k1g=; b=VNer4sy857+Y504pyFQXrP239Un90gnnO3ESAJ32+XO9OhgImZxbLc/AeCbiKbo8H588Ok /rA2zCzurBfiqAt/AYcxCzmjHB5EJkIrz/G28nx4fTcjC7ohPqeTYTWg0xVkpORghz8JL3 dVYE4McqQ32PwROEFixroFh7kUUflM8= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 56630AE2C; Mon, 28 Sep 2020 09:09:54 +0000 (UTC) Subject: Re: [PATCH v2 07/11] xen/memory: Improve compat XENMEM_acquire_resource handling To: Andrew Cooper Cc: Xen-devel , George Dunlap , Ian Jackson , Stefano Stabellini , Wei Liu , Julien Grall , Paul Durrant , =?UTF-8?Q?Micha=c5=82_Leszczy=c5=84ski?= , Hubert Jasudowicz , Tamas K Lengyel References: <20200922182444.12350-1-andrew.cooper3@citrix.com> <20200922182444.12350-8-andrew.cooper3@citrix.com> From: Jan Beulich Message-ID: <9b6c7ed2-02a4-f422-c0ab-62ca5864c7db@suse.com> Date: Mon, 28 Sep 2020 11:09:53 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200922182444.12350-8-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 22.09.2020 20:24, Andrew Cooper wrote: > @@ -446,6 +430,31 @@ int compat_memory_op(unsigned int cmd, XEN_GUEST_HANDLE_PARAM(void) compat) > > #undef XLAT_mem_acquire_resource_HNDL_frame_list > > + if ( xen_frame_list && cmp.mar.nr_frames ) > + { > + /* > + * frame_list is an input for translated guests, and an output > + * for untranslated guests. Only copy in for translated guests. > + */ > + if ( paging_mode_translate(currd) ) > + { > + compat_pfn_t *compat_frame_list = (void *)xen_frame_list; > + > + if ( !compat_handle_okay(cmp.mar.frame_list, > + cmp.mar.nr_frames) || > + __copy_from_compat_offset( > + compat_frame_list, cmp.mar.frame_list, > + 0, cmp.mar.nr_frames) ) > + return -EFAULT; > + > + /* > + * Iterate backwards over compat_frame_list[] expanding > + * compat_pfn_t to xen_pfn_t in place. > + */ > + for ( int x = cmp.mar.nr_frames - 1; x >= 0; --x ) > + xen_frame_list[x] = compat_frame_list[x]; In addition to what Paul has said, I also don't see why you resort to a signed type here. Using the available local variable i ought to be quite easy: for ( i = cmp.mar.nr_frames; i--; ) xen_frame_list[i] = compat_frame_list[i]; As an aside, considering the controversy we're having on patch 2, I find it quite interesting how you carefully allow for nr_frames being zero throughout your changes here (which, as I think is obvious, I agree you want to do). Jan