linux-kernel - [PATCH 3/8] sched: Define and initialize a flag to identify valid PASID in the task

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Date:   Mon, 20 Sep 2021 19:23:44 +0000
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Andy Lutomirski" <luto@...nel.org>,
        "Dave Hansen" <dave.hansen@...el.com>,
        "Tony Luck" <tony.luck@...el.com>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        "Joerg Roedel" <joro@...tes.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "Dave Jiang" <dave.jiang@...el.com>,
        "Jacob Jun Pan" <jacob.jun.pan@...el.com>,
        "Ashok Raj" <ashok.raj@...el.com>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>
Cc:     iommu@...ts.linux-foundation.org, "x86" <x86@...nel.org>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH 3/8] sched: Define and initialize a flag to identify valid PASID in the task

From: Peter Zijlstra <peterz@...radead.org>

Add a new field to the task structure to track whether this task
has initialized the IA32_PASID MSR (and thus holds a reference
count on the PASID for this process).

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

Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Co-developed-by: Fenghua Yu <fenghua.yu@...el.com>
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
---
 include/linux/sched.h | 4 ++++
 kernel/fork.c         | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 39039ce8ac4c..21a8cff9155c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -936,6 +936,10 @@ struct task_struct {
 	unsigned			in_eventfd_signal:1;
 #endif
 
+#ifdef CONFIG_IOMMU_SUPPORT
+	unsigned			has_valid_pasid:1;
+#endif
+
 	unsigned long			atomic_flags; /* Flags requiring atomic access. */
 
 	struct restart_block		restart_block;
diff --git a/kernel/fork.c b/kernel/fork.c
index 38681ad44c76..e379f88260eb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -967,6 +967,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	tsk->use_memdelay = 0;
 #endif
 
+#ifdef CONFIG_IOMMU_SUPPORT
+	tsk->has_valid_pasid = 0;
+#endif
+
 #ifdef CONFIG_MEMCG
 	tsk->active_memcg = NULL;
 #endif
-- 
2.33.0