[PATCH v4 07/11] sched: Define and initialize a flag to identify valid PASID in the task

Fenghua Yu
2022-02-08T01:05:07Z

From: Peter Zijlstra <peterz@infradead.org>

Add a new single bit field to the task structure to track whether this task
has initialized the IA32_PASID MSR to the mm's PASID.

Initialize the field to zero when creating a new task with fork/clone.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
v4:
- Add "Reviewed-by: Thomas Gleixner <tglx@linutronix.de>" (Thomas).

v2:
- Change condition to more accurate CONFIG_IOMMU_SVA (Jacob)

include/linux/sched.h | 3 +++
kernel/fork.c | 4 ++++
2 files changed, 7 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 75ba8aa60248..4e5de3aed410 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -938,6 +938,9 @@ struct task_struct {
/* Recursion prevention for eventfd_signal() */
unsigned in_eventfd_signal:1;
#endif
+#ifdef CONFIG_IOMMU_SVA
+ unsigned pasid_activated:1;
+#endif

unsigned long atomic_flags; /* Flags requiring atomic access. */

diff --git a/kernel/fork.c b/kernel/fork.c
index c03c6682464c..51fd1df994b7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -968,6 +968,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
tsk->use_memdelay = 0;
#endif

+#ifdef CONFIG_IOMMU_SVA
+ tsk->pasid_activated = 0;
+#endif
+
#ifdef CONFIG_MEMCG
tsk->active_memcg = NULL;
#endif
--
2.35.1