From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by mx.groups.io with SMTP id smtpd.web09.1377.1608580733958114287 for ; Mon, 21 Dec 2020 11:58:54 -0800 Authentication-Results: mx.groups.io; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=VHE4zVR3; spf=pass (domain: redhat.com, ip: 216.205.24.124, mailfrom: lersek@redhat.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608580733; 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=ScVzZf5KyWqP9N0Zo7YwDJfpGD9lh/xO+uj5oKiOafs=; b=VHE4zVR3qGglmJDnAPjuuWsHhZpPlEkrvgi0KsZR92Hl2b7qFdxJ9gFkxBSOl654RpCo2L +beDBR7BxFFhgvp/EWfawxY/i34JCHJStTbzZ93oTJBJGIXOYQAVyxAhoL6x0WNO7aGONp ulcBQRw0ZMc6k/jKII5s1iJHHLNxkQs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-45-jYiCNURQMbGXr8VU4EDW1A-1; Mon, 21 Dec 2020 14:58:51 -0500 X-MC-Unique: jYiCNURQMbGXr8VU4EDW1A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1D59259; Mon, 21 Dec 2020 19:58:50 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-114-71.ams2.redhat.com [10.36.114.71]) by smtp.corp.redhat.com (Postfix) with ESMTP id 23CA560C0F; Mon, 21 Dec 2020 19:58:48 +0000 (UTC) Subject: Re: [edk2-devel] [RFC PATCH 0/5] support CPU hot-unplug To: Ankur Arora , devel@edk2.groups.io Cc: imammedo@redhat.com, boris.ostrovsky@oracle.com References: <20201208053432.2690694-1-ankur.a.arora@oracle.com> <70e6bf5d-3d59-2e6f-4b5a-2e68cdda8108@redhat.com> <98d3701d-f51f-0909-fd79-9ed4338eb1d8@oracle.com> From: "Laszlo Ersek" Message-ID: <474dd88f-cc36-3103-5bb3-1ec2d47e1256@redhat.com> Date: Mon, 21 Dec 2020 20:58:48 +0100 MIME-Version: 1.0 In-Reply-To: <98d3701d-f51f-0909-fd79-9ed4338eb1d8@oracle.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=lersek@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 12/21/20 20:09, Ankur Arora wrote: > On 2020-12-21 6:44 a.m., Laszlo Ersek wrote: >> Hi Ankur, >> >> On 12/08/20 06:34, Ankur Arora wrote: >>> [ Resending to the correct edk2 alias this time. ] >>> >>> Hi, >>> >>> This series adds support for CPU hot-unplug with OVMF. >>> >>> Please see this in conjunction with the QEMU v2 series posted here: >>>    >>> https://lore.kernel.org/qemu-devel/20201207140739.3829993-1-imammedo@redhat.com/ >>> >>> >>> In particular, would be glad for comments on Patch 4, specifically >>> where we should be ejecting the CPU. >>> >>> Right now the ejection happens in UnplugCpus() (called from >>> CpuHotplugMmi()): >>>    +    QemuCpuhpWriteCpuSelector (mMmCpuIo, RemoveApicId); >>>    +    QemuCpuhpWriteCpuStatus (mMmCpuIo, QEMU_CPUHP_STAT_EJECTED); >>> >>> That is way too early -- given that the actual unplug will happen >>> in SmmCpuUpdate() and given that the BSPHandler() would have waited >>> for the APs multiple times before then. >>> >>> Another possibility is that the actual ejection be deferred to the >>> _EJ0 method after the return from the SMI. But, that seems like a >>> hack. Additionally, Igor points out here that this approach has >>> problems: >>>    >>> https://lore.kernel.org/qemu-devel/20201204170939.1815522-1-imammedo@redhat.com/ >>> >> >> I've filed: >> >>    https://bugzilla.tianocore.org/show_bug.cgi?id=3132 >> >> Can you please register an account in the TianoCore Bugzilla at >> , and assign the above ticket to >> yourself? >> >> And then, the URL of the new BZ ticket should be included in every >> commit message, like this: >> >> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3132 >> >> just above your S-o-b. > > Sure. Will do. >   >> No need to repost just because of this; I'll review the RFC series later. > > Actually could you hold off before reviewing the RFC series. I'll be > sending > a v2 series shortly. That does the actual unplug via > SmmCpuFeaturesRendezvousExit() > (I had described the approach elsewhere in this thread.) Sure, I can de-queue the RFC series. I planned to review it anyway in the new year; I've just done some admin stuff around the feature now. Thanks Laszlo