From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49883) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e47cW-0001Ua-Ft for qemu-devel@nongnu.org; Mon, 16 Oct 2017 11:48:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e47cT-0007mF-DV for qemu-devel@nongnu.org; Mon, 16 Oct 2017 11:48:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55438) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e47cT-0007lK-6O for qemu-devel@nongnu.org; Mon, 16 Oct 2017 11:47:57 -0400 Date: Mon, 16 Oct 2017 09:47:54 -0600 From: Alex Williamson Message-ID: <20171016094754.0ba814c1@t450s.home> In-Reply-To: <1508144183-30844-1-git-send-email-yang.zhong@intel.com> References: <1508144183-30844-1-git-send-email-yang.zhong@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 0/2] add "nopin" option in the memory-backend-file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yang Zhong Cc: qemu-devel@nongnu.org, xiaoguangrong.eric@gmail.com, ehabkost@redhat.com, pbonzini@redhat.com, anthony.xu@intel.com On Mon, 16 Oct 2017 16:56:21 +0800 Yang Zhong wrote: > Qemu does not need pin NVDIMM memory for VFIO device during VFIO > hotplug, what's more, if there is no NVDIMM hw in the test machine, > the VFIO hotplug operation will need at least 10 minutes to pin RAM > as the NVDIMM, this time is not accepted. So we add "nopin=on" option > in the memory-backed-file, which can avoid to pin RAM memory for NVDIMM. > > The new command like below: > -object memory-backend-file,id=mem0,share,nopin=on,mem-path=kvm.img,size=9161408512 > > The default of "nopin" still "off" value, which is same with previous value. If an NVDIMM is not a possible DMA target for a VFIO assigned device then it should be in a different AddressSpace from the device. If an NVDIMM can be a DMA target then it's the correct thing to do to pin it through the IOMMU for a VFIO device even if it might take considerable time to do so. Thanks, Alex