From patchwork Mon Oct 24 14:31:37 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eduardo Habkost X-Patchwork-Id: 9392283 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7459A60762 for ; Mon, 24 Oct 2016 15:06:00 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 673AD28F07 for ; Mon, 24 Oct 2016 15:06:00 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5B54B28FBB; Mon, 24 Oct 2016 15:06:00 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 0499228F07 for ; Mon, 24 Oct 2016 15:06:00 +0000 (UTC) Received: from localhost ([::1]:47277 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bygp5-0002S6-8v for patchwork-qemu-devel@patchwork.kernel.org; Mon, 24 Oct 2016 11:05:59 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56358) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bygIT-0007u7-Kf for qemu-devel@nongnu.org; Mon, 24 Oct 2016 10:32:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bygIS-0006Qw-S7 for qemu-devel@nongnu.org; Mon, 24 Oct 2016 10:32:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34916) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1bygIS-0006Qa-Mq for qemu-devel@nongnu.org; Mon, 24 Oct 2016 10:32:16 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id EE27868827; Mon, 24 Oct 2016 14:32:15 +0000 (UTC) Received: from localhost (ovpn-116-51.phx2.redhat.com [10.3.116.51]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u9OEWEN2001406; Mon, 24 Oct 2016 10:32:15 -0400 From: Eduardo Habkost To: Peter Maydell Date: Mon, 24 Oct 2016 12:31:37 -0200 Message-Id: <1477319505-20181-10-git-send-email-ehabkost@redhat.com> In-Reply-To: <1477319505-20181-1-git-send-email-ehabkost@redhat.com> References: <1477319505-20181-1-git-send-email-ehabkost@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 24 Oct 2016 14:32:16 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL 09/17] pc: Clarify FW_CFG_MAX_CPUS usage comment X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Igor Mammedov , qemu-devel@nongnu.org, Richard Henderson Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Igor Mammedov Signed-off-by: Igor Mammedov Reviewed-by: Eduardo Habkost Signed-off-by: Eduardo Habkost --- hw/i386/pc.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 6f4075f..4b97795 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -746,17 +746,15 @@ static FWCfgState *bochs_bios_init(AddressSpace *as, PCMachineState *pcms) /* FW_CFG_MAX_CPUS is a bit confusing/problematic on x86: * - * SeaBIOS needs FW_CFG_MAX_CPUS for CPU hotplug, but the CPU hotplug - * QEMU<->SeaBIOS interface is not based on the "CPU index", but on the APIC - * ID of hotplugged CPUs[1]. This means that FW_CFG_MAX_CPUS is not the - * "maximum number of CPUs", but the "limit to the APIC ID values SeaBIOS - * may see". + * For machine types prior to 1.8, SeaBIOS needs FW_CFG_MAX_CPUS for + * building MPTable, ACPI MADT, ACPI CPU hotplug and ACPI SRAT table, + * that tables are based on xAPIC ID and QEMU<->SeaBIOS interface + * for CPU hotplug also uses APIC ID and not "CPU index". + * This means that FW_CFG_MAX_CPUS is not the "maximum number of CPUs", + * but the "limit to the APIC ID values SeaBIOS may see". * - * So, this means we must not use max_cpus, here, but the maximum possible - * APIC ID value, plus one. - * - * [1] The only kind of "CPU identifier" used between SeaBIOS and QEMU is - * the APIC ID, not the "CPU index" + * So for compatibility reasons with old BIOSes we are stuck with + * "etc/max-cpus" actually being apic_id_limit */ fw_cfg_add_i16(fw_cfg, FW_CFG_MAX_CPUS, (uint16_t)pcms->apic_id_limit); fw_cfg_add_i64(fw_cfg, FW_CFG_RAM_SIZE, (uint64_t)ram_size);