[Xen-devel] [PATCH][retry 2][2/2] new platform hypervisor call to get APICIDs

[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 platform hypercall that returns the
hypervisor's cpuid to apicid table.  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.

-Mark Langsdorf
Operating System Research Center
AMD

Signed-off-by: Mark Langsdorf <mark.langsdorf@xxxxxxx>

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        Mon Mar 03 14:40:26 2008 -0600
@@ -254,21 +254,39 @@ 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;
+       u8 pinned_apicids[NR_CPUS];
 #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) {
+               struct xen_platform_op op;
+               op.cmd = XENPF_getapicids;
+               set_xen_guest_handle(op.u.getapicids.apicids, pinned_apicids);
+               op.u.getapicids.nr_cpus = NR_CPUS;
+               if (HYPERVISOR_platform_op(&op)) {
+                       /* 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 = pinned_apicids[0];
+       } 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 +330,15 @@ void __init smp_prepare_cpus(unsigned in
                        (void *)gdt_descr->address,
                        XENFEAT_writable_descriptor_tables);
 
+               if (dom0_vcpus_pinned)
+                       apicid = pinned_apicids[cpu];
+               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/xen/interface/platform.h
--- a/include/xen/interface/platform.h  Mon Mar 03 13:36:57 2008 +0000
+++ b/include/xen/interface/platform.h  Mon Mar 03 14:40:26 2008 -0600
@@ -198,6 +198,16 @@ struct xenpf_getidletime {
 };
 typedef struct xenpf_getidletime xenpf_getidletime_t;
 DEFINE_XEN_GUEST_HANDLE(xenpf_getidletime_t);
+
+#define XENPF_getapicids       54
+struct xenpf_getapicids {
+    /* IN variables */
+    /* size of apicid table */
+    uint32_t nr_cpus;
+    /* OUT variables */
+    /* Table of cpu to apicids */
+    XEN_GUEST_HANDLE(uint8) apicids;
+};
 
 struct xen_platform_op {
     uint32_t cmd;
@@ -213,6 +223,7 @@ struct xen_platform_op {
         struct xenpf_enter_acpi_sleep  enter_acpi_sleep;
         struct xenpf_change_freq       change_freq;
         struct xenpf_getidletime       getidletime;
+       struct xenpf_getapicids        getapicids;
         uint8_t                        pad[128];
     } u;
 };


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