From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: Re: Hardware support for vt-posted interrupts described in vt-directed-io-spec for assigned devices Date: Fri, 20 Mar 2015 08:04:51 -0600 Message-ID: <1426860291.3643.471.camel@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, jiang.liu@linux.intel.com To: bk rakesh Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, 2015-03-20 at 15:24 +0530, bk rakesh wrote: > Adding few more information regarding the setup which i had created to > test the vt-d posted interrupts for assigned devices, > > Hardware used for evaluating vt-posted interrupts > cpu "E5-2620 v2 @ 2.10GHz" and "S2600CP server board" > > I had used kernel-3.18 patched with "KVM-VFIO IRQ forward > control(posted by eric.auger@linaro.org)", IRQ forwarding in an ARM technology for handling level triggered interrupts, not Intel, not even x86. > "hierarchy irqdomian(posted > by jiang.liu@linux.intel.com)" and "VT-d Posted-Interrupts > support(http://lwn.net/Articles/626050/) and assigned the ixgbe 10G > NIC via vfio passthrough using qemu-kvm, But resulted in the following > dmesg output, > > [233783.657187] dmar: DRHD: handling fault status reg 602 > [233783.662926] dmar: INTR-REMAP: Request device [[02:00.0] fault index 47 > INTR-REMAP:[fault reason 36] Detected reserved fields in the IRTE entry This suggests bugs in the patch series for setting bits that are reserved on the hardware in your test system. > I had checked the hardware supported for posted interrupt capability > via capability register bit 59 (#define cap_pi_support(c) (((c) >> > 59) & 1)), as described in > "http://www.intel.com/content/www/us/en/embedded/technology/virtualization/vt-directed-io-spec.html", > Which resulted as not supported, Can anyone suggest that does this hw > support posted vt-d feature ? Your own hardware is telling you that it doesn't support it. > if not then which one to use. Personally I would have no expectation that any currently shipping hardware supports this feature. If you watch one of GregKH's talks on how the Linux community works or follow development for a while, you'll see and hear that Intel will often pre-enable features before the hardware that supports it is available. I suspect this is one of those features. Thanks, Alex