Check if any online CPU in the system is tagged as
a block interference CPU, and if so return an error
to mtrr_add_page/mtrr_del_page.
This can avoid interference to such CPUs (while allowing
userspace to handle the failures).
Signed-off-by: Marcelo Tosatti <[email protected]>
Index: linux-2.6/arch/x86/kernel/cpu/mtrr/mtrr.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ linux-2.6/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -45,6 +45,7 @@
#include <linux/smp.h>
#include <linux/syscore_ops.h>
#include <linux/rcupdate.h>
+#include <linux/sched/isolation.h>
#include <asm/cpufeature.h>
#include <asm/e820/api.h>
@@ -335,6 +336,13 @@ int mtrr_add_page(unsigned long base, un
error = -EINVAL;
replace = -1;
+ block_interf_read_lock();
+
+ if (cpumask_intersects(block_interf_cpumask, cpu_online_mask)) {
+ block_interf_read_unlock();
+ return -EPERM;
+ }
+
/* No CPU hotplug when we change MTRR entries */
cpus_read_lock();
@@ -399,6 +407,7 @@ int mtrr_add_page(unsigned long base, un
out:
mutex_unlock(&mtrr_mutex);
cpus_read_unlock();
+ block_interf_read_unlock();
return error;
}
@@ -484,6 +493,11 @@ int mtrr_del_page(int reg, unsigned long
return -ENODEV;
max = num_var_ranges;
+ block_interf_read_lock();
+ if (cpumask_intersects(block_interf_cpumask, cpu_online_mask)) {
+ block_interf_read_unlock();
+ return -EPERM;
+ }
/* No CPU hotplug when we change MTRR entries */
cpus_read_lock();
mutex_lock(&mtrr_mutex);
@@ -521,6 +535,7 @@ int mtrr_del_page(int reg, unsigned long
out:
mutex_unlock(&mtrr_mutex);
cpus_read_unlock();
+ block_interf_read_unlock();
return error;
}