[Xen-changelog] [xen stable-4.6] x86: refine nr_sockets calculation

[patchbot@xxxxxxx]

commit 3d2d3d86a8e130ca1b708244bc2e16ef1975ca99
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Dec 15 15:26:56 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Dec 15 15:26:56 2015 +0100

    x86: refine nr_sockets calculation
    
    The previous variant didn't work for non-contiguous socket numbers.
    
    Reported-by: Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Tested-by: Ed Swierk <eswierk@xxxxxxxxxxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 4217080693f9a4831e290c7a31bc6b886be5ca12
    master date: 2015-12-08 09:45:29 +0100
---
 xen/arch/x86/mpparse.c       |   21 ++++++++-------------
 xen/include/asm-x86/mpspec.h |   13 +++++++++++++
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/xen/arch/x86/mpparse.c b/xen/arch/x86/mpparse.c
index 8609f4a..837ede9 100644
--- a/xen/arch/x86/mpparse.c
+++ b/xen/arch/x86/mpparse.c
@@ -89,19 +89,14 @@ void __init set_nr_cpu_ids(unsigned int max_cpus)
 
 void __init set_nr_sockets(void)
 {
-    /*
-     * Count the actual cpus in the socket 0 and use it to calculate nr_sockets
-     * so that the latter will be always >= the actual socket number in the
-     * system even when APIC IDs from MP table are too sparse.
-     */
-    unsigned int cpus = bitmap_weight(phys_cpu_present_map.mask,
-                                      boot_cpu_data.x86_max_cores *
-                                      boot_cpu_data.x86_num_siblings);
-
-    if ( cpus == 0 )
-        cpus = 1;
-
-    nr_sockets = DIV_ROUND_UP(num_processors + disabled_cpus, cpus);
+       nr_sockets = last_physid(phys_cpu_present_map)
+                    / boot_cpu_data.x86_max_cores
+                    / boot_cpu_data.x86_num_siblings + 1;
+       if (disabled_cpus)
+               nr_sockets += (disabled_cpus - 1)
+                             / boot_cpu_data.x86_max_cores
+                             / boot_cpu_data.x86_num_siblings + 1;
+       printk(XENLOG_DEBUG "nr_sockets: %u\n", nr_sockets);
 }
 
 /*
diff --git a/xen/include/asm-x86/mpspec.h b/xen/include/asm-x86/mpspec.h
index 8ae3cd5..e3e6f50 100644
--- a/xen/include/asm-x86/mpspec.h
+++ b/xen/include/asm-x86/mpspec.h
@@ -43,6 +43,19 @@ typedef struct physid_mask physid_mask_t;
 #define physid_isset(physid, map)              test_bit(physid, (map).mask)
 #define physid_test_and_set(physid, map)       test_and_set_bit(physid, 
(map).mask)
 
+#define first_physid(map)                      find_first_bit((map).mask, \
+                                                              MAX_APICS)
+#define next_physid(id, map)                   find_next_bit((map).mask, \
+                                                             MAX_APICS, (id) + 
1)
+#define last_physid(map) ({ \
+       const unsigned long *mask = (map).mask; \
+       unsigned int id, last = MAX_APICS; \
+       for (id = find_first_bit(mask, MAX_APICS); id < MAX_APICS; \
+            id = find_next_bit(mask, MAX_APICS, (id) + 1)) \
+               last = id; \
+       last; \
+})
+
 #define physids_and(dst, src1, src2)           bitmap_and((dst).mask, 
(src1).mask, (src2).mask, MAX_APICS)
 #define physids_or(dst, src1, src2)            bitmap_or((dst).mask, 
(src1).mask, (src2).mask, MAX_APICS)
 #define physids_clear(map)                     bitmap_zero((map).mask, 
MAX_APICS)
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog