[Devel] [PATCH vz8 2/2] x86: don't enable cpuid faults if /proc/vz/cpuid_override unused

[Andrey Ryabinin]

We don't need to enable cpuid faults if /proc/vz/cpuid_override
was never used. If task was attached to ve before a write to
'cpuid_override' it will not get cpuid faults now. It shouldn't
be a problem since the proper use of 'cpuid_override' requires
stopping all containers.

https://jira.sw.ru/browse/PSBM-121823
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 arch/x86/kernel/cpuid_fault.c | 21 ++-------------------
 kernel/ve/ve.c                |  5 ++++-
 2 files changed, 6 insertions(+), 20 deletions(-)

diff --git a/arch/x86/kernel/cpuid_fault.c b/arch/x86/kernel/cpuid_fault.c
index 1e8ffacc4412..cb6c2216fa8a 100644
--- a/arch/x86/kernel/cpuid_fault.c
+++ b/arch/x86/kernel/cpuid_fault.c
@@ -1,3 +1,4 @@
+#include <linux/cpuid_override.h>
 #include <linux/gfp.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
@@ -9,25 +10,7 @@
 #include <linux/veowner.h>
 #include <linux/uaccess.h>
 
-struct cpuid_override_entry {
-	unsigned int op;
-	unsigned int count;
-	bool has_count;
-	unsigned int eax;
-	unsigned int ebx;
-	unsigned int ecx;
-	unsigned int edx;
-};
-
-#define MAX_CPUID_OVERRIDE_ENTRIES	16
-
-struct cpuid_override_table {
-	struct rcu_head rcu_head;
-	int size;
-	struct cpuid_override_entry entries[MAX_CPUID_OVERRIDE_ENTRIES];
-};
-
-static struct cpuid_override_table __rcu *cpuid_override __read_mostly;
+struct cpuid_override_table __rcu *cpuid_override __read_mostly;
 static DEFINE_SPINLOCK(cpuid_override_lock);
 
 static void cpuid_override_update(struct cpuid_override_table *new_table)
diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
index aad8ce69ca1f..0d4d0ab70369 100644
--- a/kernel/ve/ve.c
+++ b/kernel/ve/ve.c
@@ -9,6 +9,7 @@
  * 've.c' helper file performing VE sub-system initialization
  */
 
+#include <linux/cpuid_override.h>
 #include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -801,6 +802,7 @@ static void ve_attach(struct cgroup_taskset *tset)
 {
 	struct cgroup_subsys_state *css;
 	struct task_struct *task;
+	extern struct cpuid_override_table __rcu *cpuid_override;
 
 	cgroup_taskset_for_each(task, css, tset) {
 		struct ve_struct *ve = css_to_ve(css);
@@ -816,7 +818,8 @@ static void ve_attach(struct cgroup_taskset *tset)
 		/* Leave parent exec domain */
 		task->parent_exec_id--;
 
-		set_tsk_thread_flag(task, TIF_CPUID_OVERRIDE);
+		if (cpuid_override_on())
+			set_tsk_thread_flag(task, TIF_CPUID_OVERRIDE);
 		task->task_ve = ve;
 	}
 }
-- 
2.26.2