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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id qa16sm21795ejc.120.2021.10.27.07.31.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Oct 2021 07:31:24 -0700 (PDT) Date: Wed, 27 Oct 2021 16:31:23 +0200 From: Igor Mammedov To: Gavin Shan Subject: Re: [PATCH] hw/arm/virt: Expose empty NUMA nodes through ACPI Message-ID: <20211027163123.270d077b@redhat.com> In-Reply-To: References: <20211025234101.224705-1-gshan@redhat.com> <20211026114751.427205bc@redhat.com> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=imammedo@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=imammedo@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -8 X-Spam_score: -0.9 X-Spam_bar: / X-Spam_report: (-0.9 / 5.0 requ) DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peter.maydell@linaro.org, drjones@redhat.com, ehabkost@redhat.com, richard.henderson@linaro.org, qemu-devel@nongnu.org, qemu-arm@nongnu.org, shan.gavin@gmail.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 27 Oct 2021 16:20:30 +1100 Gavin Shan wrote: > On 10/26/21 8:47 PM, Igor Mammedov wrote: > > On Tue, 26 Oct 2021 07:41:01 +0800 > > Gavin Shan wrote: > > > >> The empty NUMA nodes, where no memory resides, aren't exposed > >> through ACPI SRAT table. It's not user preferred behaviour because > >> the corresponding memory node devices are missed from the guest > >> kernel as the following example shows, and memory can't be hot > >> added to these empty NUMA nodes at later point. > > > > a error message one gets would be useful here. > > > > btw: > > memory hotplug seems to work for x86 without adding empty nodes. > > So it beg a question, if absence of empty nodes is the issue here. > > > > Yes, the memory can be still hot added even the empty NUMA nodes > aren't exposed. However, we still need to expose them so that > the guest kernel has the information as the users specifies. commit message says that memory can't be hotplugged though ... so what doesn't work/is broken currently. Question is why do we need to expose empty nodes that aren't warranted by any present hardware (cpu/mem)? (so far I see it as extra burden on qemu without any gain) SRAT is typically used to describe startup configuration, any changes to topology later during runtime are made using _PXM objects. > > I will make the commit log more precise in v2. > > >> > >> /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64 \ > >> -accel kvm -machine virt,gic-version=host \ > >> -cpu host -smp 4,sockets=2,cores=2,threads=1 \ > >> -m 1024M,slots=16,maxmem=64G \ > >> -object memory-backend-ram,id=mem0,size=512M \ > >> -object memory-backend-ram,id=mem1,size=512M \ > >> -numa node,nodeid=0,cpus=0-1,memdev=mem0 \ > >> -numa node,nodeid=1,cpus=2-3,memdev=mem1 \ > >> -numa node,nodeid=2 \ > >> -numa node,nodeid=3 \ > >> : > >> guest# ls /sys/devices/system/node | grep node > >> node0 > >> node1 > >> node2 > >> > >> This exposes these empty NUMA nodes through ACPI SRAT table. With > >> this applied, the corresponding memory node devices can be found > >> from the guest. Note that the hotpluggable capability is explicitly > >> given to these empty NUMA nodes for sake of completeness. > >> > >> guest# ls /sys/devices/system/node | grep node > >> node0 > >> node1 > >> node2 > >> node3 > >> > >> Signed-off-by: Gavin Shan > >> --- > >> hw/arm/virt-acpi-build.c | 14 +++++++++----- > >> 1 file changed, 9 insertions(+), 5 deletions(-) > >> > >> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > >> index 674f902652..a4c95b2f64 100644 > >> --- a/hw/arm/virt-acpi-build.c > >> +++ b/hw/arm/virt-acpi-build.c > >> @@ -526,6 +526,7 @@ build_srat(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > >> const CPUArchIdList *cpu_list = mc->possible_cpu_arch_ids(ms); > >> AcpiTable table = { .sig = "SRAT", .rev = 3, .oem_id = vms->oem_id, > >> .oem_table_id = vms->oem_table_id }; > >> + MemoryAffinityFlags flags; > >> > >> acpi_table_begin(&table, table_data); > >> build_append_int_noprefix(table_data, 1, 4); /* Reserved */ > >> @@ -547,12 +548,15 @@ build_srat(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > >> > >> mem_base = vms->memmap[VIRT_MEM].base; > >> for (i = 0; i < ms->numa_state->num_nodes; ++i) { > >> - if (ms->numa_state->nodes[i].node_mem > 0) { > >> - build_srat_memory(table_data, mem_base, > >> - ms->numa_state->nodes[i].node_mem, i, > >> - MEM_AFFINITY_ENABLED); > >> - mem_base += ms->numa_state->nodes[i].node_mem; > >> + if (ms->numa_state->nodes[i].node_mem) { > >> + flags = MEM_AFFINITY_ENABLED; > >> + } else { > >> + flags = MEM_AFFINITY_ENABLED | MEM_AFFINITY_HOTPLUGGABLE; > >> } > >> + > >> + build_srat_memory(table_data, mem_base, > >> + ms->numa_state->nodes[i].node_mem, i, flags); > >> + mem_base += ms->numa_state->nodes[i].node_mem; > >> } > >> > >> if (ms->nvdimms_state->is_enabled) { > > > > Thanks, > Gavin >