From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [RFC][PATCH] KVM: Introduce direct MSI message injection for in-kernel irqchips Date: Mon, 24 Oct 2011 11:45:28 +0200 Message-ID: <4EA533B8.4040407@redhat.com> References: <4EA13917.7070401@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm , "Michael S. Tsirkin" To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:5960 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754375Ab1JXJqL (ORCPT ); Mon, 24 Oct 2011 05:46:11 -0400 In-Reply-To: <4EA13917.7070401@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10/21/2011 11:19 AM, Jan Kiszka wrote: > Currently, MSI messages can only be injected to in-kernel irqchips by > defining a corresponding IRQ route for each message. This is not only > unhandy if the MSI messages are generated "on the fly" by user space, > IRQ routes are a limited resource that user space as to manage > carefully. By itself, this does not provide enough value to offset the cost of a new ABI, especially as userspace will need to continue supporting the old method for a very long while. > By providing a direct injection with, we can both avoid using up limited > resources and simplify the necessary steps for user land. The API > already provides a channel (flags) to revoke an injected but not yet > delivered message which will become important for in-kernel MSI-X vector > masking support. > With the new feature it may be worthwhile, but I'd like to see the whole thing, with numbers attached. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.