[xen stable-4.6] x86: possibly bring up all CPUs even if not all are supposed to be used

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[xen stable-4.6] x86: possibly bring up all CPUs even if not all are supposed to be used

patchbot
commit 91cf29f7c680f399382ef50b422c1eb0a92a5b2e
Author:     Jan Beulich <[hidden email]>
AuthorDate: Mon Jul 30 14:20:22 2018 +0200
Commit:     Jan Beulich <[hidden email]>
CommitDate: Mon Jul 30 14:20:22 2018 +0200

    x86: possibly bring up all CPUs even if not all are supposed to be used
   
    Reportedly Intel CPUs which can't broadcast #MC to all targeted
    cores/threads because some have CR4.MCE clear will shut down. Therefore
    we want to keep CR4.MCE enabled when offlining a CPU, and we need to
    bring up all CPUs in order to be able to set CR4.MCE in the first place.
   
    The use of clear_in_cr4() in cpu_mcheck_disable() was ill advised
    anyway, and to avoid future similar mistakes I'm removing clear_in_cr4()
    altogether right here.
   
    Signed-off-by: Jan Beulich <[hidden email]>
    Reviewed-by: Andrew Cooper <[hidden email]>
    Reviewed-by: Roger Pau Monné <[hidden email]>
    Reviewed-by: Wei Liu <[hidden email]>
    master commit: 8797d20a6ec2dd75195585a107ce345c51c0a59a
    master date: 2018-07-19 13:43:33 +0100
---
 xen/arch/x86/cpu/common.c           |  4 ++++
 xen/arch/x86/cpu/mcheck/mce_intel.c |  2 --
 xen/arch/x86/mpparse.c              | 15 +++++++++++----
 xen/arch/x86/setup.c                | 18 +++++++++++++++---
 xen/include/asm-x86/processor.h     |  6 ------
 5 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 1fb8f1b5d8..7d1c32e335 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -15,6 +15,7 @@
 #include <public/sysctl.h> /* for XEN_INVALID_{SOCKET,CORE}_ID */
 
 #include "cpu.h"
+#include "mcheck/x86_mca.h"
 
 static bool_t __cpuinitdata use_xsave = 1;
 boolean_param("xsave", use_xsave);
@@ -209,6 +210,9 @@ static void __init early_cpu_detect(void)
  c->x86_capability[0] = cap0;
  c->x86_capability[4] = cap4;
 
+ if (c->x86_vendor != X86_VENDOR_AMD)
+ park_offline_cpus = !mce_disabled;
+
  initialize_cpu_data(0);
 }
 
diff --git a/xen/arch/x86/cpu/mcheck/mce_intel.c b/xen/arch/x86/cpu/mcheck/mce_intel.c
index 193366b002..a8afb9ba2d 100644
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -628,8 +628,6 @@ static void clear_cmci(void)
 
 static void cpu_mcheck_disable(void)
 {
-    clear_in_cr4(X86_CR4_MCE);
-
     if (cmci_support && !mce_disabled)
         clear_cmci();
 }
diff --git a/xen/arch/x86/mpparse.c b/xen/arch/x86/mpparse.c
index 837ede96d3..c834ce30cb 100644
--- a/xen/arch/x86/mpparse.c
+++ b/xen/arch/x86/mpparse.c
@@ -69,19 +69,26 @@ physid_mask_t phys_cpu_present_map;
 
 void __init set_nr_cpu_ids(unsigned int max_cpus)
 {
+ unsigned int tot_cpus = num_processors + disabled_cpus;
+
  if (!max_cpus)
- max_cpus = num_processors + disabled_cpus;
+ max_cpus = tot_cpus;
  if (max_cpus > NR_CPUS)
  max_cpus = NR_CPUS;
  else if (!max_cpus)
  max_cpus = 1;
  printk(XENLOG_INFO "SMP: Allowing %u CPUs (%d hotplug CPUs)\n",
        max_cpus, max_t(int, max_cpus - num_processors, 0));
- nr_cpu_ids = max_cpus;
+
+ if (!park_offline_cpus)
+ tot_cpus = max_cpus;
+ nr_cpu_ids = min(tot_cpus, NR_CPUS + 0u);
+ if (park_offline_cpus && nr_cpu_ids < num_processors)
+ printk(XENLOG_WARNING "SMP: Cannot bring up %u further CPUs\n",
+       num_processors - nr_cpu_ids);
 
 #ifndef nr_cpumask_bits
- nr_cpumask_bits = (max_cpus + (BITS_PER_LONG - 1)) &
-  ~(BITS_PER_LONG - 1);
+ nr_cpumask_bits = ROUNDUP(nr_cpu_ids, BITS_PER_LONG);
  printk(XENLOG_DEBUG "NR_CPUS:%u nr_cpumask_bits:%u\n",
        NR_CPUS, nr_cpumask_bits);
 #endif
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 8adba9d19c..58ac554f39 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -616,7 +616,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 {
     char *memmap_type = NULL;
     char *cmdline, *kextra, *loader;
-    unsigned int initrdidx, domcr_flags = DOMCRF_s3_integrity;
+    unsigned int initrdidx, num_parked = 0, domcr_flags = DOMCRF_s3_integrity;
     multiboot_info_t *mbi = __va(mbi_p);
     module_t *mod = (module_t *)__va(mbi->mods_addr);
     unsigned long nr_pages, raw_max_page, modules_headroom, *module_map;
@@ -1319,7 +1319,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     else
     {
         set_nr_cpu_ids(max_cpus);
-        max_cpus = nr_cpu_ids;
+        if ( !max_cpus )
+            max_cpus = nr_cpu_ids;
     }
 
     /* Low mappings were only needed for some BIOS table parsing. */
@@ -1431,15 +1432,26 @@ void __init noreturn __start_xen(unsigned long mbi_p)
         /* Set up node_to_cpumask based on cpu_to_node[]. */
         numa_add_cpu(i);        
 
-        if ( (num_online_cpus() < max_cpus) && !cpu_online(i) )
+        if ( (park_offline_cpus || num_online_cpus() < max_cpus) &&
+             !cpu_online(i) )
         {
             int ret = cpu_up(i);
             if ( ret != 0 )
                 printk("Failed to bring up CPU %u (error %d)\n", i, ret);
+            else if ( num_online_cpus() > max_cpus )
+            {
+                ret = cpu_down(i);
+                if ( !ret )
+                    ++num_parked;
+                else
+                    printk("Could not re-offline CPU%u (%d)\n", i, ret);
+            }
         }
     }
 
     printk("Brought up %ld CPUs\n", (long)num_online_cpus());
+    if ( num_parked )
+        printk(XENLOG_INFO "Parked %u CPUs\n", num_parked);
     smp_cpus_done();
 
     do_initcalls();
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index ca535bb22b..02d5118c78 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -390,12 +390,6 @@ static always_inline void set_in_cr4 (unsigned long mask)
     write_cr4(read_cr4() | mask);
 }
 
-static always_inline void clear_in_cr4 (unsigned long mask)
-{
-    mmu_cr4_features &= ~mask;
-    write_cr4(read_cr4() & ~mask);
-}
-
 /*
  *      NSC/Cyrix CPU configuration register indexes
  */
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6


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