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 BB6B9C43331 for ; Tue, 31 Mar 2020 15:27:41 +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 92B2620786 for ; Tue, 31 Mar 2020 15:27:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 92B2620786 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 1jJInS-0004Dw-0J; Tue, 31 Mar 2020 15:27:22 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jJInP-0004Dr-Pr for xen-devel@lists.xenproject.org; Tue, 31 Mar 2020 15:27:19 +0000 X-Inumbo-ID: 1b94929a-7364-11ea-b4f4-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 1b94929a-7364-11ea-b4f4-bc764e2007e4; Tue, 31 Mar 2020 15:27:19 +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 F1019ABC2; Tue, 31 Mar 2020 15:27:17 +0000 (UTC) Subject: Re: [PATCH 11/11] x86/ucode/amd: Rework parsing logic in cpu_request_microcode() To: Andrew Cooper References: <20200331100531.4294-1-andrew.cooper3@citrix.com> <20200331100531.4294-12-andrew.cooper3@citrix.com> <3bcfdf14-7785-0319-26aa-b80926eff7ed@citrix.com> From: Jan Beulich Message-ID: <4e47ddba-d951-d573-1357-199207d28f43@suse.com> Date: Tue, 31 Mar 2020 17:27:12 +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: <3bcfdf14-7785-0319-26aa-b80926eff7ed@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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 17:19, Andrew Cooper wrote: > On 31/03/2020 16:07, Jan Beulich wrote: >> On 31.03.2020 12:05, Andrew Cooper wrote: >>> @@ -269,55 +265,25 @@ static int apply_microcode(const struct microcode_patch *patch) >>> return 0; >>> } >>> >>> -static int scan_equiv_cpu_table( >>> - const void *data, >>> - size_t size_left, >>> - size_t *offset) >>> +static int scan_equiv_cpu_table(const struct container_equiv_table *et) >>> { >>> const struct cpu_signature *sig = &this_cpu(cpu_sig); >>> - const struct mpbhdr *mpbuf; >>> - const struct equiv_cpu_entry *eq; >>> - unsigned int i, nr; >>> - >>> - if ( size_left < (sizeof(*mpbuf) + 4) || >>> - (mpbuf = data + *offset + 4, >>> - size_left - sizeof(*mpbuf) - 4 < mpbuf->len) ) >>> - { >>> - printk(XENLOG_WARNING "microcode: No space for equivalent cpu table\n"); >>> - return -EINVAL; >>> - } >>> - >>> - *offset += mpbuf->len + CONT_HDR_SIZE; /* add header length */ >>> - >>> - if ( mpbuf->type != UCODE_EQUIV_CPU_TABLE_TYPE ) >>> - { >>> - printk(KERN_ERR "microcode: Wrong microcode equivalent cpu table type field\n"); >>> - return -EINVAL; >>> - } >>> - >>> - if ( mpbuf->len == 0 || mpbuf->len % sizeof(*eq) || >>> - (eq = (const void *)mpbuf->data, >>> - nr = mpbuf->len / sizeof(*eq), >>> - eq[nr - 1].installed_cpu) ) >> Did this last check get lost? I can't seem to be able to identify >> any possible replacement. > > Given the lack of a spec, I'm unsure whether to keep it or not. > > It is necessary in the backport of patch 1, because find_equiv_cpu_id() > doesn't have mpbuf->len to hand, and relies on the sentinel to find the > end of the table. > > OTOH, the new logic will cope perfectly well without a sentinel. Okay. >>> static struct microcode_patch *cpu_request_microcode(const void *buf, size_t size) >>> { >>> const struct microcode_patch *saved = NULL; >>> struct microcode_patch *patch = NULL; >>> - size_t offset = 0, saved_size = 0; >>> + size_t saved_size = 0; >>> int error = 0; >>> - unsigned int cpu = smp_processor_id(); >>> - const struct cpu_signature *sig = &per_cpu(cpu_sig, cpu); >>> >>> - if ( size < 4 || >>> - *(const uint32_t *)buf != UCODE_MAGIC ) >>> + while ( size ) >>> { >>> - printk(KERN_ERR "microcode: Wrong microcode patch file magic\n"); >>> - error = -EINVAL; >>> - goto out; >>> - } >>> - >>> - /* >>> - * Multiple container file support: >>> - * 1. check if this container file has equiv_cpu_id match >>> - * 2. If not, fast-fwd to next container file >>> - */ >>> - while ( offset < size ) >>> - { >>> - error = scan_equiv_cpu_table(buf, size - offset, &offset); >>> - >>> - if ( !error || error != -ESRCH ) >>> - break; >>> + const struct container_equiv_table *et; >>> + bool skip_ucode; >>> >>> - error = container_fast_forward(buf, size - offset, &offset); >>> - if ( error == -ENODATA ) >>> + if ( size < 4 || *(const uint32_t *)buf != UCODE_MAGIC ) >>> { >>> - ASSERT(offset == size); >>> + printk(XENLOG_ERR "microcode: Wrong microcode patch file magic\n"); >>> + error = -EINVAL; >>> break; >>> } >>> - if ( error ) >>> + >>> + /* Move over UCODE_MAGIC. */ >>> + buf += 4; >>> + size -= 4; >>> + >>> + if ( size < sizeof(*et) || >>> + (et = buf)->type != UCODE_EQUIV_CPU_TABLE_TYPE || >>> + size - sizeof(*et) < et->len || >>> + et->len % sizeof(et->eq[0]) ) >>> { >>> - printk(KERN_ERR "microcode: CPU%d incorrect or corrupt container file\n" >>> - "microcode: Failed to update patch level. " >>> - "Current lvl:%#x\n", cpu, sig->rev); >>> + printk(XENLOG_ERR "microcode: Bad equivalent cpu table\n"); >>> + error = -EINVAL; >>> break; >>> } >>> - } >>> >>> - if ( error ) >>> - { >>> - /* >>> - * -ENODATA here means that the blob was parsed fine but no matching >>> - * ucode was found. Don't return it to the caller. >>> - */ >>> - if ( error == -ENODATA ) >>> - error = 0; >>> - >>> - goto out; >>> - } >>> + /* Move over the Equiv table. */ >>> + buf += sizeof(*et) + et->len; >>> + size -= sizeof(*et) + et->len; >>> + >>> + error = scan_equiv_cpu_table(et); >>> + if ( error && error != -ESRCH ) >>> + break; >> With this the only non-zero value left for error is -ESRCH. >> Hence ... >> >>> + /* -ESRCH means no applicable microcode in this container. */ >>> + skip_ucode = error == -ESRCH; >> ... perhaps omit the "== -ESRCH" here, moving the comment up >> ahead of the if()? > > That doesn't work, because you've got to reset error to 0 somewhere (to > avoid it leaking out if you don't find suitable microcode), and it can't > be before checking for errors in general.  It can't easily become a > conditional because skip_ucode needs setting unconditionally. I don't follow - what's wrong with /* -ESRCH means no applicable microcode in this container. */ if ( error && error != -ESRCH ) break; skip_ucode = error; error = 0; ? > I have been debating quite heavily whether -ESRCH is best here, or using > -ve, 0 and 1.  However, this doesn't lead to prettier code AFAICT, and > gains an ambiguous use for a variable named "error". I'm fine with that choice of yours. Jan