Any comment on this?
On Fri, Oct 25, 2013 at 11:32:10AM +0200, Vasilis Liaskovitis wrote:
> 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)
> --
> 1.7.10.4
>
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