From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [Xen-devel] [PATCH RESEND] fix MSI injection on Xen Date: Wed, 27 Jan 2016 12:41:38 -0500 Message-ID: <20160127174138.GF2258@char.us.oracle.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org To: Stefano Stabellini Cc: xen-devel@lists.xensource.com, Wei Liu , qemu-devel@nongnu.org, mst@redhat.com List-Id: xen-devel@lists.xenproject.org On Wed, Jan 13, 2016 at 02:59:09PM +0000, Stefano Stabellini wrote: > On Xen MSIs can be remapped into pirqs, which are a type of event > channels. It's mostly for the benefit of PCI passthrough devices, to > avoid the overhead of interacting with the emulated lapic. > > However remapping interrupts and MSIs is also supported for emulated > devices, such as the e1000 and virtio-net. > > When an interrupt or an MSI is remapped into a pirq, masking and > unmasking is done by masking and unmasking the event channel. The > masking bit on the PCI config space or MSI-X table should be ignored, > but it isn't at the moment. > > As a consequence emulated devices which use MSI or MSI-X, such as > virtio-net, don't work properly (the guest doesn't receive any > notifications). The mechanism was working properly when xen_apic was By xen_apic I presume the Linux Xen APIC code? > introduced, but I haven't narrowed down which commit in particular is > causing the regression. It sounds like the issue was due to the Xen APIC code? Or am I misreading it?