This patch adds a _PXM object to seabios CPU objects. The _PXM value is derived from CPU SRAT entries, so build_ssdt needs to be called after build_srat for this to work.
The motivation for this patch is a CPU hot-unplug/hot-plug bug observed when using seabios and a 3.11 linux guest kernel on a multi-NUMA node qemu/kvm VM. The linux guest kernel parses the SRAT CPU entries at boot time and stores them in the array __apicid_to_node. When a CPU is hot-removed, the linux guest kernel resets the removed CPU's __apicid_to_node entry to NO_NUMA_NODE (kernel commit c4c60524). When the removed cpu is hot-added again, the linux kernel looks up the hot-added cpu object's _PXM value instead of somehow re-using the SRAT entry info (acpi_map_cpu2node calls acpi_get_node which calls acpi_get_pxm). If the _PXM value is not found, the CPU is assumed to be on node 0, and it is hot-plugged in the wrong NUMA node.
Which is the preferred OSPM way of looking up a CPU's proximity info at hotplug time? Is it the CPU object's _PXM value, or the already-parsed CPU SRAT entry? Or maybe both ways are valid?
This issue may require a kernel fix alternatively or additionally to the seabios fix: The kernel can save the originally parsed SRAT entry info somewhere before it resets it at hot-remove time, and use that info on hot-plug time if the _PXM value is missing for the hot-plugged CPU BIOS object. This way CPU hot-plug works well against a BIOS with no CPU _PXM info.
Any comments / thoughts are welcome. --- src/fw/acpi.c | 8 +++++++- src/fw/ssdt-proc.dsl | 2 ++ 2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/src/fw/acpi.c b/src/fw/acpi.c index 8de24c9..85c04fd 100644 --- a/src/fw/acpi.c +++ b/src/fw/acpi.c @@ -23,6 +23,7 @@ #include "src/fw/acpi-dsdt.hex"
u32 acpi_pm1a_cnt VARFSEG; +struct srat_processor_affinity *cpu;
static void build_header(struct acpi_table_header *h, u32 sig, int len, u8 rev) @@ -244,6 +245,7 @@ encodeLen(u8 *ssdt_ptr, int length, int bytes) #define PROC_OFFSET_CPUHEX (*ssdt_proc_name - *ssdt_proc_start + 2) #define PROC_OFFSET_CPUID1 (*ssdt_proc_name - *ssdt_proc_start + 4) #define PROC_OFFSET_CPUID2 (*ssdt_proc_id - *ssdt_proc_start) +#define PROC_OFFSET_CPUPXM (*ssdt_proc_pxm - *ssdt_proc_start) #define PROC_SIZEOF (*ssdt_proc_end - *ssdt_proc_start) #define PROC_AML (ssdp_proc_aml + *ssdt_proc_start)
@@ -372,6 +374,7 @@ build_ssdt(void) *(ssdt_ptr++) = '_';
// build Processor object for each processor + struct srat_processor_affinity *core = cpu; int i; for (i=0; i<acpi_cpus; i++) { memcpy(ssdt_ptr, PROC_AML, PROC_SIZEOF); @@ -379,7 +382,9 @@ build_ssdt(void) ssdt_ptr[PROC_OFFSET_CPUHEX+1] = getHex(i); ssdt_ptr[PROC_OFFSET_CPUID1] = i; ssdt_ptr[PROC_OFFSET_CPUID2] = i; + ssdt_ptr[PROC_OFFSET_CPUPXM] = core->proximity_lo; ssdt_ptr += PROC_SIZEOF; + core++; }
// build "Method(NTFY, 2) {If (LEqual(Arg0, 0x00)) {Notify(CP00, Arg1)} ...}" @@ -497,6 +502,7 @@ build_srat(void) int i; u64 curnode;
+ cpu = core; for (i = 0; i < max_cpu; ++i) { core->type = SRAT_PROCESSOR; core->length = sizeof(*core); @@ -620,10 +626,10 @@ acpi_setup(void)
struct fadt_descriptor_rev1 *fadt = build_fadt(pci); ACPI_INIT_TABLE(fadt); - ACPI_INIT_TABLE(build_ssdt()); ACPI_INIT_TABLE(build_madt()); ACPI_INIT_TABLE(build_hpet()); ACPI_INIT_TABLE(build_srat()); + ACPI_INIT_TABLE(build_ssdt()); if (pci->device == PCI_DEVICE_ID_INTEL_ICH9_LPC) ACPI_INIT_TABLE(build_mcfg_q35());
diff --git a/src/fw/ssdt-proc.dsl b/src/fw/ssdt-proc.dsl index 407d61e..373cdd7 100644 --- a/src/fw/ssdt-proc.dsl +++ b/src/fw/ssdt-proc.dsl @@ -32,6 +32,8 @@ DefinitionBlock ("ssdt-proc.aml", "SSDT", 0x01, "BXPC", "BXSSDT", 0x1) * also updating the C code. */ Name(_HID, "ACPI0007") + ACPI_EXTRACT_NAME_BYTE_CONST ssdt_proc_pxm + Name(_PXM, 0xBB) External(CPMA, MethodObj) External(CPST, MethodObj) External(CPEJ, MethodObj)