Re: [PATCH v8] x86, apic, kexec, Documentation: Add disable_cpu_apic kernel parameter
On Thu, Nov 28, 2013 at 10:34:27AM +0900, HATAYAMA Daisuke wrote:
[..]
> int generic_processor_info(int apicid, int version)
> {
> int cpu, max = nr_cpu_ids;
> - bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
> + /*
> + * boot_cpu_physical_apicid is designed to have the apicid
> + * returned by read_apic_id(), i.e, the apicid of the
> + * currently booting-up processor. However, on some platforms,
> + * it is temporarilly modified by the apicid reported as BSP
> + * through MP table. Concretely:
> + *
> + * - arch/x86/kernel/mpparse.c: MP_processor_info()
> + * - arch/x86/mm/amdtopology.c: amd_numa_init()
> + * - arch/x86/platform/visws/visws_quirks.c: MP_processor_info()
> + *
> + * This function is executed with the modified
> + * boot_cpu_physical_apicid. So, disabled_cpu_apicid kernel
> + * parameter doesn't work to disable APs on kdump 2nd kernel.
> + *
> + * Since fixing handling of boot_cpu_physical_apicid requires
> + * another discussion and tests on each platform, we leave it
> + * for now and here we use read_apic_id() directly in this
> + * function, generic_processor_info().
> + */
> + bool boot_cpu_detected = physid_isset(read_apic_id(),
> phys_cpu_present_map);
>
> + if (disabled_cpu_apicid != BAD_APICID &&
> + disabled_cpu_apicid != read_apic_id() &&
> + disabled_cpu_apicid == apicid) {
> + int thiscpu = num_processors + disabled_cpus;
> +
> + pr_warning("ACPI: Disabling requested cpu."
> +" Processor %d/0x%x ignored.\n",
> +thiscpu, apicid);
> +
> + disabled_cpus++;
> + return -ENODEV;
> + }
> +
> /*
>* If boot cpu has not been detected yet, then only allow upto
>* nr_cpu_ids - 1 processors and keep one slot free for boot cpu
>*/
> if (!boot_cpu_detected && num_processors >= nr_cpu_ids - 1 &&
> - apicid != boot_cpu_physical_apicid) {
> + apicid != read_apic_id()) {
I thought of using read_apic_id() only for disabled_cpu_apicid case.
Existing code seems to be working fine with boot_cpu_physical_apicid.
Instead of converting rest of the code to read_apic_id() we should fix
notion of boot_cpu_physical_id in a separate cleanup patch series.
IOW, can we please use read_apic_id() only for the case of
disabled_cpu_apicid and leave rest of the code untouched. And handle all
the cleanup in separate patch series.
Thanks
Vivek
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Re: [PATCH v8] x86, apic, kexec, Documentation: Add disable_cpu_apic kernel parameter
On Thu, Nov 28, 2013 at 10:34:27AM +0900, HATAYAMA Daisuke wrote:
[..]
int generic_processor_info(int apicid, int version)
{
int cpu, max = nr_cpu_ids;
- bool boot_cpu_detected = physid_isset(boot_cpu_physical_apicid,
+ /*
+ * boot_cpu_physical_apicid is designed to have the apicid
+ * returned by read_apic_id(), i.e, the apicid of the
+ * currently booting-up processor. However, on some platforms,
+ * it is temporarilly modified by the apicid reported as BSP
+ * through MP table. Concretely:
+ *
+ * - arch/x86/kernel/mpparse.c: MP_processor_info()
+ * - arch/x86/mm/amdtopology.c: amd_numa_init()
+ * - arch/x86/platform/visws/visws_quirks.c: MP_processor_info()
+ *
+ * This function is executed with the modified
+ * boot_cpu_physical_apicid. So, disabled_cpu_apicid kernel
+ * parameter doesn't work to disable APs on kdump 2nd kernel.
+ *
+ * Since fixing handling of boot_cpu_physical_apicid requires
+ * another discussion and tests on each platform, we leave it
+ * for now and here we use read_apic_id() directly in this
+ * function, generic_processor_info().
+ */
+ bool boot_cpu_detected = physid_isset(read_apic_id(),
phys_cpu_present_map);
+ if (disabled_cpu_apicid != BAD_APICID
+ disabled_cpu_apicid != read_apic_id()
+ disabled_cpu_apicid == apicid) {
+ int thiscpu = num_processors + disabled_cpus;
+
+ pr_warning(ACPI: Disabling requested cpu.
+ Processor %d/0x%x ignored.\n,
+thiscpu, apicid);
+
+ disabled_cpus++;
+ return -ENODEV;
+ }
+
/*
* If boot cpu has not been detected yet, then only allow upto
* nr_cpu_ids - 1 processors and keep one slot free for boot cpu
*/
if (!boot_cpu_detected num_processors = nr_cpu_ids - 1
- apicid != boot_cpu_physical_apicid) {
+ apicid != read_apic_id()) {
I thought of using read_apic_id() only for disabled_cpu_apicid case.
Existing code seems to be working fine with boot_cpu_physical_apicid.
Instead of converting rest of the code to read_apic_id() we should fix
notion of boot_cpu_physical_id in a separate cleanup patch series.
IOW, can we please use read_apic_id() only for the case of
disabled_cpu_apicid and leave rest of the code untouched. And handle all
the cleanup in separate patch series.
Thanks
Vivek
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
