From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49969) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZwsyE-0003bG-Mx for qemu-devel@nongnu.org; Thu, 12 Nov 2015 09:35:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zwsy9-0008BF-Ic for qemu-devel@nongnu.org; Thu, 12 Nov 2015 09:35:26 -0500 Received: from mailout2.w1.samsung.com ([210.118.77.12]:42363) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zwsy9-0008B5-DM for qemu-devel@nongnu.org; Thu, 12 Nov 2015 09:35:21 -0500 Received: from eucpsbgm1.samsung.com (unknown [203.254.199.244]) by mailout2.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NXP005VLHUUN770@mailout2.w1.samsung.com> for qemu-devel@nongnu.org; Thu, 12 Nov 2015 14:35:18 +0000 (GMT) From: Pavel Fedin References: <00fb01d11d19$fc458f20$f4d0ad60$@samsung.com> <1447337819.3946.35.camel@redhat.com> In-reply-to: <1447337819.3946.35.camel@redhat.com> Date: Thu, 12 Nov 2015 17:35:17 +0300 Message-id: <014c01d11d57$5a101a20$0e304e60$@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=UTF-8 Content-transfer-encoding: quoted-printable Content-language: ru Subject: Re: [Qemu-devel] [PATCH] vfio: Fix handling VFIO_IOMMU_GET_INFO results List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: 'Alex Williamson' Cc: qemu-devel@nongnu.org Hello! > > Kernel headers define VFIO_IOMMU_INFO_PGSIZES flag, however it has > > actually been never used, probably by mistake which now became a = part > > of the ABI. The kernel always sets info.flags to 0: >=20 > I don't see how this implies that it becomes part of the ABI. In = fact, > as the defacto userspace driver for vfio, QEMU honoring the flag and = not > using the value the kernel provides implies the ABI is still valid. = We > should fix the kernel instead. Well... I intentionally put two links to LXR. From the very beginning, = this ioctl returned valid page sizes. And it never set this flag. We = simply cannot have a kernel which does not report page sizes. If we fix qemu, it will automatically start working with all available = kernels which are there in the wild. If we fix kernel, older versions = will still not work, however they can. That's why i think that we should adapt qemu to what already exists. = But, well, you are The Boss, so you can just say "i don't care". So, = just let me now if you strongly disagree with this. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia