[Patch v3 1/2] x86/smp: count the number of online physical processor in the system

From: Chao Gao <chao.gao@intel.com>
To: xen-devel@lists.xen.org
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Jan Beulich <jbeulich@suse.com>, Chao Gao <chao.gao@intel.com>
Subject: [Patch v3 1/2] x86/smp: count the number of online physical processor in the system
Date: Wed,  9 May 2018 06:01:32 +0800	[thread overview]
Message-ID: <1525816893-36669-1-git-send-email-chao.gao@intel.com> (raw)

Mainly for the patch behind which relies on 'nr_phys_cpus' to estimate
the time needed for microcode update in the worst case.

Signed-off-by: Chao Gao <chao.gao@intel.com>
---
v3:
 - new

---
 xen/arch/x86/smpboot.c    | 13 +++++++++++++
 xen/include/asm-x86/smp.h |  3 +++
 2 files changed, 16 insertions(+)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 86fa410..c3c3558 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -67,6 +67,8 @@ unsigned int __read_mostly nr_sockets;
 cpumask_t **__read_mostly socket_cpumask;
 static cpumask_t *secondary_socket_cpumask;
 
+unsigned int __read_mostly nr_phys_cpus;
+
 struct cpuinfo_x86 cpu_data[NR_CPUS];
 
 u32 x86_cpu_to_apicid[NR_CPUS] __read_mostly =
@@ -262,6 +264,10 @@ static void set_cpu_sibling_map(int cpu)
         cpumask_set_cpu(cpu, per_cpu(cpu_sibling_mask, cpu));
     }
 
+    /* Increase physical processor count when a new cpu comes up */
+    if ( cpumask_weight(per_cpu(cpu_sibling_mask, cpu)) == 1 )
+        nr_phys_cpus++;
+
     if ( c[cpu].x86_max_cores == 1 )
     {
         cpumask_copy(per_cpu(cpu_core_mask, cpu),
@@ -1156,6 +1162,13 @@ remove_siblinginfo(int cpu)
             cpu_data[sibling].booted_cores--;
     }
 
+    /*
+     * Decrease physical processor count when all threads of a physical
+     * processor go down
+     */
+    if ( cpumask_weight(per_cpu(cpu_sibling_mask, cpu)) == 1 )
+        nr_phys_cpus--;
+
     for_each_cpu(sibling, per_cpu(cpu_sibling_mask, cpu))
         cpumask_clear_cpu(cpu, per_cpu(cpu_sibling_mask, sibling));
     cpumask_clear(per_cpu(cpu_sibling_mask, cpu));
diff --git a/xen/include/asm-x86/smp.h b/xen/include/asm-x86/smp.h
index 4e5f673..910888a 100644
--- a/xen/include/asm-x86/smp.h
+++ b/xen/include/asm-x86/smp.h
@@ -65,6 +65,9 @@ uint32_t get_cur_idle_nums(void);
  */
 extern unsigned int nr_sockets;
 
+/* The number of online physical CPUs in this system */
+extern unsigned int nr_phys_cpus;
+
 void set_nr_sockets(void);
 
 /* Representing HT and core siblings in each socket. */
-- 
1.8.3.1


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