From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v2 1/4] x86/MSI-X: be more careful during teardown Date: Mon, 30 Mar 2015 11:05:30 +0100 Message-ID: <55191FEA.4000800@citrix.com> References: <5512F1B3020000780006D924@mail.emea.novell.com> <5512F2C2020000780006D941@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YcWZb-0006gg-C2 for xen-devel@lists.xenproject.org; Mon, 30 Mar 2015 10:05:35 +0000 In-Reply-To: <5512F2C2020000780006D941@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 25/03/15 16:39, Jan Beulich wrote: > When a device gets detached from a guest, pciback will clear its > command register, thus disabling both memory and I/O decoding. The > disabled memory decoding, however, has an effect on the MSI-X table > accesses the hypervisor does: These won't have the intended effect > anymore. Even worse, for PCIe devices (but not SR-IOV virtual > functions) such accesses may (will?) be treated as Unsupported > Requests, causing respective errors to be surfaced, potentially in the > form of NMIs that may be fatal to the hypervisor or Dom0 is different > ways. Hence rather than carrying out these accesses, we should avoid > them where we can, and use alternative (e.g. PCI config space based) > mechanisms to achieve at least the same effect. > > Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper