From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46388) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dogM9-0003UV-TS for qemu-devel@nongnu.org; Sun, 03 Sep 2017 21:39:22 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dogM4-00018l-Td for qemu-devel@nongnu.org; Sun, 03 Sep 2017 21:39:17 -0400 Received: from mail.cn.fujitsu.com ([183.91.158.132]:54396 helo=heian.cn.fujitsu.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dogM4-00016S-2Y for qemu-devel@nongnu.org; Sun, 03 Sep 2017 21:39:12 -0400 References: <20170901154542.5687-1-cascardo@canonical.com> <20170901161118.GQ7570@localhost.localdomain> From: Dou Liyang Message-ID: <2ab3aaef-c6d7-ae3d-808b-f947dcb3ed1c@cn.fujitsu.com> Date: Mon, 4 Sep 2017 09:38:47 +0800 MIME-Version: 1.0 In-Reply-To: <20170901161118.GQ7570@localhost.localdomain> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] x86/acpi: build SRAT when memory hotplug is enabled List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost , Thadeu Lima de Souza Cascardo Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Igor Mammedov , Paolo Bonzini , Richard Henderson Hi Eduardo, Thadeu, At 09/02/2017 12:11 AM, Eduardo Habkost wrote: > On Fri, Sep 01, 2017 at 12:45:42PM -0300, Thadeu Lima de Souza Cascardo wrote: >> Linux uses SRAT to determine the maximum memory in a system, which is >> used to determine whether to use the swiotlb for IOMMU or not for a >> device that supports only 32 bits of addresses. > > Do you have a pointer to the corresponding Linux code, for > reference? Which SRAT entries Linux uses to make this decision? > >> >> When there is no NUMA configuration, qemu will not build SRAT. And when >> memory hotplug is done, some Linux device drivers start failing. >> >> Tested by running with -m 512M,slots=8,maxmem=1G, adding the memory, >> putting that online and using the system. Without the patch, swiotlb is >> not used and ATA driver fails. With the patch, swiotlb is used, no >> driver failure is observed. >> >> Signed-off-by: Thadeu Lima de Souza Cascardo > > As far as I can see, this will only add APIC entries and a memory > affinity entry for the first 640KB (which would be obviously > wrong) if pcms->numa_nodes is 0. > In my opinion, this may also add the hotpluggable memory, and see the following commemts. /* * Entry is required for Windows to enable memory hotplug in OS * and for Linux to enable SWIOTLB when booted with less than ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * 4G of RAM. Windows works better if the entry sets proximity * to the highest NUMA node in the machine. * Memory devices may override proximity set by this entry, * providing _PXM method if necessary. */ if (hotplugabble_address_space_size) { numamem = acpi_data_push(table_data, sizeof *numamem); build_srat_memory(numamem, pcms->hotplug_memory.base, hotplugabble_address_space_size, pcms->numa_nodes - 1, MEM_AFFINITY_HOTPLUGGABLE | MEM_AFFINITY_ENABLED); } Thanks, dou. > Once we apply the "Fix SRAT memory building in case of node 0 > without RAM" patch from Dou Liyang, no memory affinity entries > will be generated if pcms->numa_nodes is 0. Would this cause the > problem to happen again? > > >> --- >> hw/i386/acpi-build.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c >> index 98dd424678..fb94249779 100644 >> --- a/hw/i386/acpi-build.c >> +++ b/hw/i386/acpi-build.c >> @@ -2645,6 +2645,9 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine) >> GArray *tables_blob = tables->table_data; >> AcpiSlicOem slic_oem = { .id = NULL, .table_id = NULL }; >> Object *vmgenid_dev; >> + ram_addr_t hotplugabble_address_space_size = >> + object_property_get_int(OBJECT(pcms), PC_MACHINE_MEMHP_REGION_SIZE, >> + NULL); >> >> acpi_get_pm_info(&pm); >> acpi_get_misc_info(&misc); >> @@ -2708,7 +2711,7 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine) >> build_tpm2(tables_blob, tables->linker); >> } >> } >> - if (pcms->numa_nodes) { >> + if (pcms->numa_nodes || hotplugabble_address_space_size) { >> acpi_add_table(table_offsets, tables_blob); >> build_srat(tables_blob, tables->linker, machine); >> if (have_numa_distance) { >> -- >> 2.11.0 >> >