From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH] x86: don't change affinity with interrupt unmasked Date: Wed, 25 Mar 2015 18:12:17 +0000 Message-ID: <5512FA81.4000708@citrix.com> References: <550C4D62020000780006C258@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Yapmy-0005l0-5i for xen-devel@lists.xenproject.org; Wed, 25 Mar 2015 18:12:24 +0000 In-Reply-To: <550C4D62020000780006C258@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich , xen-devel Cc: Keir Fraser List-Id: xen-devel@lists.xenproject.org On 20/03/15 16:40, Jan Beulich wrote: > With ->startup unmasking the IRQ, setting the affinity afterwards > without masking the IRQ again is invalid namely for MSI (which can't > have their affinity updated atomically). > > Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper > --- > Changing the affinity of non-maskable MSI IRQs seems bogus too Agreed. Their affinity can clearly only be changed safely by a device driver which can guarantee that an interrupt will not be generated during the vulnerable period. This further implies that Xen can't even safely set an affinity to start with... > , but I > can't immediately see what we can do about this (better than disabling > affinity changes for them). If we used interrupt remapping properly (which we don't), we could update the effective affinity without changing any device configuration, but this still doesn't provide a solution for the many systems out there without (functional) interrupt remapping. ~Andrew