Drivers: hv: Setup a mapping for Hyper-V's notion cpu ID

On win8 (ws2012), incoming vmbus interrupt load can be spread across all
available VCPUs in the guest. On a per-channel basis, the interrupts can
be bound to specific CPUs. The Linux notion of cpu ID may be different
from that of the hypervisor's. Setup a mapping structure.
Signed-off-by: NK. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: NHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/hv.c

@@ -137,6 +137,8 @@ int hv_init(void)
 	memset(hv_context.synic_event_page, 0, sizeof(void *) * NR_CPUS);
 	memset(hv_context.synic_message_page, 0,
 	       sizeof(void *) * NR_CPUS);
+	memset(hv_context.vp_index, 0,
+	       sizeof(int) * NR_CPUS);
 
 	max_leaf = query_hypervisor_info();
 
@@ -296,6 +298,7 @@ void hv_synic_init(void *irqarg)
 	union hv_synic_siefp siefp;
 	union hv_synic_sint shared_sint;
 	union hv_synic_scontrol sctrl;
+	u64 vp_index;
 
 	u32 irq_vector = *((u32 *)(irqarg));
 	int cpu = smp_processor_id();
@@ -355,6 +358,14 @@ void hv_synic_init(void *irqarg)
 	wrmsrl(HV_X64_MSR_SCONTROL, sctrl.as_uint64);
 
 	hv_context.synic_initialized = true;
+
+	/*
+	 * Setup the mapping between Hyper-V's notion
+	 * of cpuid and Linux' notion of cpuid.
+	 * This array will be indexed using Linux cpuid.
+	 */
+	rdmsrl(HV_X64_MSR_VP_INDEX, vp_index);
+	hv_context.vp_index[cpu] = (u32)vp_index;
 	return;
 
 cleanup:

drivers/hv/hyperv_vmbus.h

@@ -502,6 +502,16 @@ struct hv_context {
 
 	void *synic_message_page[NR_CPUS];
 	void *synic_event_page[NR_CPUS];
+	/*
+	 * Hypervisor's notion of virtual processor ID is different from
+	 * Linux' notion of CPU ID. This information can only be retrieved
+	 * in the context of the calling CPU. Setup a map for easy access
+	 * to this information:
+	 *
+	 * vp_index[a] is the Hyper-V's processor ID corresponding to
+	 * Linux cpuid 'a'.
+	 */
+	u32 vp_index[NR_CPUS];
 };
 
 extern struct hv_context hv_context;