From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752773AbaLWAiT (ORCPT ); Mon, 22 Dec 2014 19:38:19 -0500 Received: from mga02.intel.com ([134.134.136.20]:27764 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751024AbaLWAiS convert rfc822-to-8bit (ORCPT ); Mon, 22 Dec 2014 19:38:18 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,627,1413270000"; d="scan'208";a="651905629" From: "Zhang, Yang Z" To: Paolo Bonzini , "Wu, Feng" , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "x86@kernel.org" , "Gleb Natapov" , "dwmw2@infradead.org" , "joro@8bytes.org" , Alex Williamson , Jiang Liu CC: "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , KVM list , Eric Auger Subject: RE: [v3 06/26] iommu, x86: No need to migrating irq for VT-d Posted-Interrupts Thread-Topic: [v3 06/26] iommu, x86: No need to migrating irq for VT-d Posted-Interrupts Thread-Index: AQHQFiFw/2wcwNXVUk6mLzPIG8E78JyVcJswgAC8KvCAAAEAoIAAJl0AgAYPrcA= Date: Tue, 23 Dec 2014 00:37:46 +0000 Message-ID: References: <1418397300-10870-1-git-send-email-feng.wu@intel.com> <1418397300-10870-7-git-send-email-feng.wu@intel.com> <54941326.4080405@redhat.com> In-Reply-To: <54941326.4080405@redhat.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paolo Bonzini wrote on 2014-12-19: > > > On 19/12/2014 02:46, Zhang, Yang Z wrote: >>> If the IRQ is posted, its affinity is controlled by guest (irq >>> <---> vCPU <----> pCPU), it has no effect when host changes its affinity. >> >> That's the problem: User is able to changes it in host but it never >> takes effect since it is actually controlled by guest. I guess it >> will break the IRQ balance too. > > I don't think that's a problem. > > Controlling the affinity in the host affects which CPU in the host > takes care of signaling the guest. > > If this signaling is done directly by the chipset, there is no need to > do anything in the host and thus the host affinity can be bypassed. I don't quite understand it. If user set an interrupt's affinity to a CPU, but he still see the interrupt delivers to other CPUs in host. Do you think it is a right behavior? > > Paolo Best regards, Yang