Please ignore this!
> From: Linuxarm [mailto:linuxarm-boun...@huawei.com] On Behalf Of Salil Mehta > Sent: Wednesday, January 29, 2020 11:51 AM > To: qemu-devel@nongnu.org; qemu-...@nongnu.org > Cc: peter.mayd...@linaro.org; drjo...@redhat.com; sa...@linux.intel.com; > m...@redhat.com; Linuxarm <linux...@huawei.com>; eric.au...@redhat.com; > pbonzini <pbonz...@redhat.com>; Igor Mammedov <imamm...@redhat.com>; > ler...@redhat.com > Subject: [Question] Regarding presence of duplicate ACPI CPU entries at two > nodes > \\_SB.CXXX and \\_SB.CPUS.CXXX of namespace > > Hello, > > Observation: > If we launch Linux Guest VM using QEMU(running on any type host. I am using > x86) > with > CPU based on any ARM64 architecture then I could see QEMU populating ACPI > nodes > related to same CPU at 2 places of the ACPI namespace: > 1. \\_SB.CXXX > 2. \\_SB.CPUS.CXXX > > Above results in Guest VM showing duplicate CPU entries in the sysfs for the > same CPUS. > I could make out the entries under \\_SB.CPUS.XXX are part of the container. > > estuary:/$ ls -al /sys/bus/acpi/devices/ > > Observation 1: (belongs to \\_SB.C00X) > ACPI0007:00 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0007:00 > ACPI0007:01 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0007:01 > ACPI0007:02 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0007:02 > ACPI0007:03 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0007:03 > ACPI0007:04 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0007:04 > ACPI0007:05 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0007:05 > > Observation 2: (belongs to \\_SB.CPUS.C00X and under container ACPI0010:00 > part > of \\_SB.CPUS) > ACPI0007:06 > -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0010:00/ACPI0007:06 > ACPI0007:07 > -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0010:00/ACPI0007:07 > ACPI0007:08 > -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0010:00/ACPI0007:08 > ACPI0007:09 > -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0010:00/ACPI0007:09 > ACPI0007:0a > -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0010:00/ACPI0007:0a > ACPI0007:0b > -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0010:00/ACPI0007:0b > ACPI0010:00 -> ../../../devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0010:00 > > > estuary:/$ cat /sys/bus/acpi/devices/ACPI0010\:00/path > \_SB_.CPUS > > estuary:/$ cat /sys/bus/acpi/devices/ACPI0007\:00/uid > 0 > estuary:/$ cat /sys/bus/acpi/devices/ACPI0007\:00/path > \_SB_.C000 > > estuary:/$ cat /sys/bus/acpi/devices/ACPI0007\:06/uid > 0 > estuary:/$ cat /sys/bus/acpi/devices/ACPI0007\:06/path > \_SB_.CPUS.C000 > > > > QEMU Code Excerpt: > I could trace with in QEMU AML code, the CPUS are being appended at 2 places: > > > Code 1. File: hw/arm/virt-acpi-build.c (Cause of Observation 1 i.e. > \\_SB.CXXX ) > > static void acpi_dsdt_add_cpus(Aml *scope, int smp_cpus) > { > uint16_t i; > > for (i = 0; i < smp_cpus; i++) { --->{should be possible cpus anyways} > Aml *dev = aml_device("C%.03X", i); > aml_append(dev, aml_name_decl("_HID", aml_string("ACPI0007"))); > aml_append(dev, aml_name_decl("_UID", aml_int(i))); > aml_append(scope, dev); > } > } > > > Code 2. File: hw/acpi/cpu.c (Cause of Observation 2 i.e. \\_SB.CPUS.CXXX) > > void build_cpus_aml(..) > { > [...] > cpus_dev = aml_device("\\_SB.CPUS"); > { > [...] > /* build Processor object for each processor */ > for (i = 0; i < arch_ids->len; i++) { > Aml *dev; > Aml *uid = aml_int(i); > GArray *madt_buf = g_array_new(0, 1, 1); > int arch_id = arch_ids->cpus[i].arch_id; > > if (opts.acpi_1_compatible && arch_id < 255) { > dev = aml_processor(i, 0, 0, CPU_NAME_FMT, i); > } else { > dev = aml_device(CPU_NAME_FMT, i); > aml_append(dev, aml_name_decl("_HID", > aml_string("ACPI0007"))); > aml_append(dev, aml_name_decl("_UID", uid)); > } > [...] > } > [...] > } > > > > Questions: > Q1. I could not understand the purpose of keeping acpi_dsdt_add_cpus() after > the code 2. > was introduced as part of the below change and which is already adding > CPUS > related > AML to \\_SB.CPUS namespace? > > acpi: cpuhp: add CPU devices AML with _STA method > commit 5e1b5d93887b52eede156f846b6c4c5c8bbcfcdb > > Q2. Do we really require CPUs being added by acpi_dsdt_add_cpus() in > \\_SB.CXXX > Namespace OR is it a stray code left? > > > > Please help to correct if there is a gap in my understanding here and please > forgive me if I have terribly missed out something very basic here. > > Many thanks! > > Best Regards > Salil >
