[Xen-devel] [PATCH][retry 3][2/2] new vcpu op call to get physical CPU information

[Mark Langsdorf <mark.langsdorf@xxxxxxx>]

Some AMD machines have APIC IDs that not equal to CPU IDs.  In
the default Xen configuration, ACPI calls on these machines
can get confused.  This shows up most noticeably when running
AMD PowerNow!.  The only solution is for dom0 to get the
hypervisor's cpuid to apicid table when needed (ie, when dom0
vcpus are pinned).

Make dom0 call a new vcpu op hypercall that returns
architecture dependent information about the physical cpu if
and only iff the vcpus are pinned.  In this particular case,
the information is the underlying ACPIID and APICIDs for the
physical processor.  Only the APICIDs are used in this case
as the ACPIIDs are set up correctly by the ACPI subsystem
already.

The decision logic (dom0_vcpus_pinned) is currently hard-coded 
but should be passed from the hypervisor.  Keir wrote that he 
would take care of that when he suggested this solution.

I have tested this on my 4p/16 core machine and it works.  I
would appreciate testing on other boxes.


diff -r 1cf7ba68d855 drivers/xen/core/smpboot.c
--- a/drivers/xen/core/smpboot.c        Mon Mar 03 13:36:57 2008 +0000
+++ b/drivers/xen/core/smpboot.c        Tue Mar 04 15:45:19 2008 -0600
@@ -254,21 +254,35 @@ static void __cpuinit cpu_initialize_con
        spin_unlock(&ctxt_lock);
 }
 
+int dom0_vcpus_pinned = 1;
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
        unsigned int cpu;
        struct task_struct *idle;
+       int apicid;
 #ifdef __x86_64__
        struct desc_ptr *gdt_descr;
 #else
        struct Xgt_desc_struct *gdt_descr;
 #endif
 
-       boot_cpu_data.apicid = 0;
+       if (dom0_vcpus_pinned) {
+               vcpu_get_physid_t cpu_data;
+               if (HYPERVISOR_vcpu_op(VCPUOP_get_physid, 0, &cpu_data)) {
+                       /* failed to get valid data from hypervisor */
+                       printk(KERN_ERR "failed to get valid APIC ID 
information\n");
+                       dom0_vcpus_pinned = 0;
+                       apicid = 0;
+               }
+               else
+                       apicid = GET_APICID_FROM_PHYSID(cpu_data.phys_id);
+       } else
+               apicid = 0;
+       boot_cpu_data.apicid = apicid;
        cpu_data[0] = boot_cpu_data;
 
-       cpu_2_logical_apicid[0] = 0;
-       x86_cpu_to_apicid[0] = 0;
+       cpu_2_logical_apicid[0] = apicid;
+       x86_cpu_to_apicid[0] = apicid;
 
        current_thread_info()->cpu = 0;
 
@@ -312,11 +326,20 @@ void __init smp_prepare_cpus(unsigned in
                        (void *)gdt_descr->address,
                        XENFEAT_writable_descriptor_tables);
 
+               if (dom0_vcpus_pinned) {
+                       vcpu_get_physid_t cpu_data;
+                       if (HYPERVISOR_vcpu_op(VCPUOP_get_physid, cpu, 
&cpu_data)) {
+                               dom0_vcpus_pinned = 0;
+                               apicid = cpu;
+                       } else
+                               apicid = 
GET_APICID_FROM_PHYSID(cpu_data.phys_id); 
+               } else
+                       apicid = cpu;
                cpu_data[cpu] = boot_cpu_data;
-               cpu_data[cpu].apicid = cpu;
-
-               cpu_2_logical_apicid[cpu] = cpu;
-               x86_cpu_to_apicid[cpu] = cpu;
+               cpu_data[cpu].apicid = apicid;
+
+               cpu_2_logical_apicid[cpu] = apicid;
+               x86_cpu_to_apicid[cpu] = apicid;
 
                idle = fork_idle(cpu);
                if (IS_ERR(idle))
diff -r 1cf7ba68d855 include/asm-x86_64/mach-xen/asm/smp.h
--- a/include/asm-x86_64/mach-xen/asm/smp.h     Mon Mar 03 13:36:57 2008 +0000
+++ b/include/asm-x86_64/mach-xen/asm/smp.h     Tue Mar 04 15:45:19 2008 -0600
@@ -146,5 +146,11 @@ static __inline int logical_smp_processo
 #define cpu_physical_id(cpu)           boot_cpu_id
 #endif
 
+#define APICMASK                       0xff
+#define APICSHIFT                      0
+#define ACPIMASK                       0xff00
+#define ACPISHIFT                      8
+#define GET_APICID_FROM_PHYSID(physid) (physid & APICMASK) >> APICSHIFT;
+#define GET_ACPIID_FROM_PHYSID(physid) (physid & ACPIMASK) >> ACPISHIFT;
 #endif
 
diff -r 1cf7ba68d855 include/xen/interface/vcpu.h
--- a/include/xen/interface/vcpu.h      Mon Mar 03 13:36:57 2008 +0000
+++ b/include/xen/interface/vcpu.h      Tue Mar 04 15:45:19 2008 -0600
@@ -182,6 +182,17 @@ DEFINE_XEN_GUEST_HANDLE(vcpu_register_vc
 /* Send an NMI to the specified VCPU. @extra_arg == NULL. */
 #define VCPUOP_send_nmi             11
 
+/* 
+ * Get the physical ID information for a pinned vcpu's underlying
+ * physical processor.  The phyiscal ID informmation is architecture
+ * defined, but would ACPI and APIC IDs on x86 processors.
+ */
+#define VCPUOP_get_physid           12 /* arg == vcpu_get_physid_t */
+struct vcpu_get_physid {
+    uint64_t phys_id;
+};
+typedef struct vcpu_get_physid vcpu_get_physid_t;
+DEFINE_XEN_GUEST_HANDLE(vcpu_get_physid_t);
 #endif /* __XEN_PUBLIC_VCPU_H__ */
 
 /*


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