From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37412) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dnoXX-00074w-Da for qemu-devel@nongnu.org; Fri, 01 Sep 2017 12:11:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dnoXT-0002Dg-Ck for qemu-devel@nongnu.org; Fri, 01 Sep 2017 12:11:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33693) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dnoXT-0002DF-42 for qemu-devel@nongnu.org; Fri, 01 Sep 2017 12:11:23 -0400 Date: Fri, 1 Sep 2017 13:11:18 -0300 From: Eduardo Habkost Message-ID: <20170901161118.GQ7570@localhost.localdomain> References: <20170901154542.5687-1-cascardo@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170901154542.5687-1-cascardo@canonical.com> 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: Thadeu Lima de Souza Cascardo Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Igor Mammedov , Paolo Bonzini , Richard Henderson , Dou Liyang 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. 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 > -- Eduardo