From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35686) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fp6wg-0002jA-0Y for qemu-devel@nongnu.org; Mon, 13 Aug 2018 03:07:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fp6wf-0006dB-3e for qemu-devel@nongnu.org; Mon, 13 Aug 2018 03:07:17 -0400 Date: Mon, 13 Aug 2018 09:07:13 +0200 From: Igor Mammedov Message-ID: <20180813090713.76d7f710@redhat.com> In-Reply-To: <20180810182835.GZ15372@localhost.localdomain> References: <1533910017-55158-1-git-send-email-imammedo@redhat.com> <20180810180106.26e1f642@redhat.com> <20180810182835.GZ15372@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] acpi: SRAT: do not create reserved gap entries List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: qemu-devel@nongnu.org, qemu-stable@nongnu.org, lersek@redhat.com, mst@redhat.com On Fri, 10 Aug 2018 15:28:35 -0300 Eduardo Habkost wrote: > On Fri, Aug 10, 2018 at 06:01:06PM +0200, Igor Mammedov wrote: > > On Fri, 10 Aug 2018 16:06:57 +0200 > > Igor Mammedov wrote: > > > > > Commit 848a1cc1e8b04 while introducing SRAT entries for DIMM and NVDIMM > > > also introduced fake entries for gaps between memory devices, assuming > > > that we need all possible range covered with SRAT entries. > > > And it did it wrong since gap would overlap with preceeding entry. > > > Reproduced with following CLI: > > > > > > -m 1G,slots=4,maxmem=8 \ > > > -object memory-backend-ram,size=1G,id=m0 \ > > > -device pc-dimm,memdev=m0,addr=0x101000000 \ > > > -object memory-backend-ram,size=1G,id=m1 \ > > > -device pc-dimm,memdev=m1 > > > > > > However recent development (10efd7e108) showed that gap entries might > > > be not need. And indeed testing with WS2008DC-WS2016DC guests range > > > shows that memory hotplug works just fine without gap entries. > > > > > > So rather than fixing gap entry borders, just drop them altogether > > > and simplify code around it. > > > > > > Spotted-by: Laszlo Ersek > > > Signed-off-by: Igor Mammedov > > > --- > > > There is no need to update reference blobs since gaps beween dimms > > > aren't generated by any exsting test case. > > > > > > Considering issue is not visible by default lets just merge it into 3.1 > > > and stable 3.0.1 > > Pls ignore it for now I'll need to do more extensive testing with old kernels, > > we might need these holes for old kernels or even new ones. > > /me goes to read kernel code > > > > /per spec possible to hotplug range could be in SRAT, > > even though I don't like it bu we might end up with static > > partitioning of hotplug area between nodes like on bare metal > > to avoid chasing after unknown requirements from windows / > > Does that mean we might want to pair DIMM slots with NUMA nodes > in advance? Do you have a suggestion on how the command-line > would look like, in this case? > > Maybe "-numa mem-slot,slot=X,node=Y"? it's either, to make it per slot (it implies fixed maximum size per slot) or a bit more flexible maxmem per node, might be something like: -numa memory,node=X,maxmem=Y