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=-5.2 required=3.0 tests=BAYES_00, 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 14816C388F9 for ; Sun, 8 Nov 2020 23:26:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA9FD206DB for ; Sun, 8 Nov 2020 23:26:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728016AbgKHX0B (ORCPT ); Sun, 8 Nov 2020 18:26:01 -0500 Received: from mga01.intel.com ([192.55.52.88]:53447 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727929AbgKHX0B (ORCPT ); Sun, 8 Nov 2020 18:26:01 -0500 IronPort-SDR: PNuotPER4rnD6JFNMg4okKauh+DUm1kwdGCoi7yP3MqXzbgWdsG/eW7WRBi0JVQ55w7JklF5vj lUUGmQrSkrtw== X-IronPort-AV: E=McAfee;i="6000,8403,9799"; a="187674999" X-IronPort-AV: E=Sophos;i="5.77,462,1596524400"; d="scan'208";a="187674999" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Nov 2020 15:26:00 -0800 IronPort-SDR: x7QIRRuMi3bh+85h6knCHRfekbCoEwqsYZDqjIL2wQYho9XxStdGjLBngGkka+xrL5RYp+m5Pb WLKWJD3KgxdA== X-IronPort-AV: E=Sophos;i="5.77,462,1596524400"; d="scan'208";a="540602801" Received: from araj-mobl1.jf.intel.com ([10.255.228.179]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Nov 2020 15:25:59 -0800 Date: Sun, 8 Nov 2020 15:25:57 -0800 From: "Raj, Ashok" To: David Woodhouse Cc: Jason Gunthorpe , Dan Williams , "Tian, Kevin" , "Jiang, Dave" , Bjorn Helgaas , "vkoul@kernel.org" , "Dey, Megha" , "maz@kernel.org" , "bhelgaas@google.com" , "tglx@linutronix.de" , "alex.williamson@redhat.com" , "Pan, Jacob jun" , "Liu, Yi L" , "Lu, Baolu" , "Kumar, Sanjay K" , "Luck, Tony" , "jing.lin@intel.com" , "kwankhede@nvidia.com" , "eric.auger@redhat.com" , "parav@mellanox.com" , "rafael@kernel.org" , "netanelg@mellanox.com" , "shahafs@mellanox.com" , "yan.y.zhao@linux.intel.com" , "pbonzini@redhat.com" , "Ortiz, Samuel" , "Hossain, Mona" , "dmaengine@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "kvm@vger.kernel.org" , Ashok Raj Subject: Re: [PATCH v4 06/17] PCI: add SIOV and IMS capability detection Message-ID: <20201108232557.GA32074@araj-mobl1.jf.intel.com> References: <20201104135415.GX2620339@nvidia.com> <20201106131415.GT2620339@nvidia.com> <20201106164850.GA85879@otc-nc-03> <20201106175131.GW2620339@nvidia.com> <20201107001207.GA2620339@nvidia.com> <20201108181124.GA28173@araj-mobl1.jf.intel.com> <20da76a4cd2e984a307d673e26f76ab73bd820f4.camel@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20da76a4cd2e984a307d673e26f76ab73bd820f4.camel@infradead.org> User-Agent: Mutt/1.9.1 (2017-09-22) Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Sun, Nov 08, 2020 at 06:34:55PM +0000, David Woodhouse wrote: > > > > When we do interrupt remapping support in guest which would be required > > if we support x2apic in guest, I think this is something we should look into more > > carefully to make this work. > > No, interrupt remapping is not required for X2APIC in guests > > They can have X2APIC and up to 32768 CPUs without needing interrupt How is this made available today without interrupt remapping? I thought without IR, the destination ID is still limited to only 8 bits? On native, even if you have less than 255 cpu's but the APICID are sparsly distributed due to platform rules, the x2apic id could be more than 8 bits. Which is why the spec requires IR when x2apic is enabled. > remapping at all. Only if they want more than 32768 vCPUs, or to do > nested virtualisation and actually remap for the benefit of *their* > (L2+) guests would they need IR.