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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 70EFBC2D0F1 for ; Tue, 31 Mar 2020 14:51:42 +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 4F4B52078B for ; Tue, 31 Mar 2020 14:51:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F4B52078B Authentication-Results: mail.kernel.org; dmarc=none (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 4.89) (envelope-from ) id 1jJIEk-0000xN-R3; Tue, 31 Mar 2020 14:51:30 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jJIEj-0000xF-BJ for xen-devel@lists.xenproject.org; Tue, 31 Mar 2020 14:51:29 +0000 X-Inumbo-ID: 19732d50-735f-11ea-b58d-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 19732d50-735f-11ea-b58d-bc764e2007e4; Tue, 31 Mar 2020 14:51:27 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id CA66CB03F; Tue, 31 Mar 2020 14:51:26 +0000 (UTC) Subject: Re: [PATCH 09/11] x86/ucode/amd: Remove gratuitous memory allocations from cpu_request_microcode() To: Andrew Cooper References: <20200331100531.4294-1-andrew.cooper3@citrix.com> <20200331100531.4294-10-andrew.cooper3@citrix.com> From: Jan Beulich Message-ID: Date: Tue, 31 Mar 2020 16:51:25 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200331100531.4294-10-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: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Xen-devel , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 31.03.2020 12:05, Andrew Cooper wrote: > @@ -497,57 +456,54 @@ static struct microcode_patch *cpu_request_microcode(const void *buf, size_t siz > * It's possible the data file has multiple matching ucode, > * lets keep searching till the latest version > */ > - while ( (error = get_ucode_from_buffer_amd(mc_amd, buf, size, > - &offset)) == 0 ) > + buf += offset; > + size -= offset; > { > - /* > - * If the new ucode covers current CPU, compare ucodes and store the > - * one with higher revision. > - */ > - if ( (microcode_fits(mc_amd->mpb) != MIS_UCODE) && > - (!saved || (compare_header(mc_amd->mpb, saved) == NEW_UCODE)) ) > + while ( size ) > { > - xfree(saved); > - saved = mc_amd->mpb; > - } > - else > - { > - xfree(mc_amd->mpb); > - mc_amd->mpb = NULL; > - } > + const struct container_microcode *mc; > + > + if ( size < sizeof(*mc) || > + (mc = buf)->type != UCODE_UCODE_TYPE || > + size - sizeof(*mc) < mc->len || > + !verify_patch_size(mc->len) ) > + { > + printk(XENLOG_ERR "microcode: Bad microcode data\n"); > + error = -EINVAL; > + break; > + } > > - if ( offset >= size ) > - break; > + /* > + * If the new ucode covers current CPU, compare ucodes and store the > + * one with higher revision. > + */ > + if ( (microcode_fits(mc->patch) != MIS_UCODE) && > + (!saved || (compare_header(mc->patch, saved) == NEW_UCODE)) ) > + { > + saved = mc->patch; > + saved_size = mc->len; > + } > > - /* > - * 1. Given a situation where multiple containers exist and correct > - * patch lives on a container that is not the last container. > - * 2. We match equivalent ids using find_equiv_cpu_id() from the > - * earlier while() (On this case, matches on earlier container > - * file and we break) > - * 3. Proceed to while ( (error = get_ucode_from_buffer_amd(mc_amd, > - * buf, size, &offset)) == 0 ) > - * 4. Find correct patch using microcode_fits() and apply the patch > - * (Assume: apply_microcode() is successful) > - * 5. The while() loop from (3) continues to parse the binary as > - * there is a subsequent container file, but... > - * 6. ...a correct patch can only be on one container and not on any > - * subsequent ones. (Refer docs for more info) Therefore, we > - * don't have to parse a subsequent container. So, we can abort > - * the process here. > - * 7. This ensures that we retain a success value (= 0) to 'error' > - * before if ( mpbuf->type != UCODE_UCODE_TYPE ) evaluates to > - * false and returns -EINVAL. > - */ > - if ( offset + SECTION_HDR_SIZE <= size && > - *(const uint32_t *)(buf + offset) == UCODE_MAGIC ) > - break; > + /* Move over the microcode blob. */ > + buf += sizeof(*mc) + mc->len; > + size -= sizeof(*mc) + mc->len; > + > + /* > + * Peek ahead. If we see the start of another container, we've > + * exhaused all microcode blobs in this container. Exit cleanly. > + */ > + if ( size >= 4 && *(const uint32_t *)buf == UCODE_MAGIC ) > + break; While, as already indicated, I agree with shrinking the big comment, I think point 6 is what wants retaining in some form - it's not obvious at all why a subsequent container couldn't contain a higher rev ucode than what we've found. That comment refers us to docs, but I couldn't find anything to this effect in PM Vol 2. Assuming this indeed documented and true, with the comment extended accordingly Reviewed-by: Jan Beulich Jan