[PATCH 3/5] arm64: mm: Use cpumask in flush_context()

[y00318929]

From: Yunfeng Ye <yeyunfeng@xxxxxxxxxx>

Currently, all CPUs are selected to flush TLB in flush_context().
In order to prepare for flushing only part of the CPUs TLB, we use
asid_housekeeping_mask and use cpumask_or() instead of cpumask_setall().

Signed-off-by: Yunfeng Ye <yeyunfeng@xxxxxxxxxx>
---
 arch/arm64/mm/context.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
index 380c7b05c36b..e402997aa1c2 100644
--- a/arch/arm64/mm/context.c
+++ b/arch/arm64/mm/context.c
@@ -11,6 +11,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/mm.h>
+#include <linux/cpumask.h>
 
 #include <asm/cpufeature.h>
 #include <asm/mmu_context.h>
@@ -32,6 +33,7 @@ static unsigned long *asid_map;
 static DEFINE_PER_CPU(atomic64_t, active_asids);
 static DEFINE_PER_CPU(u64, reserved_asids);
 static cpumask_t tlb_flush_pending;
+static const struct cpumask *asid_housekeeping_mask;
 
 static struct asid_bitmap pinned_asid;
 
@@ -129,17 +131,23 @@ static inline bool asid_gen_match(u64 asid)
 	return asid_match(asid, asid_read_generation());
 }
 
+static const struct cpumask *flush_cpumask(void)
+{
+	return asid_housekeeping_mask;
+}
+
 static void flush_context(void)
 {
 	int i;
 	u64 asid;
+	const struct cpumask *cpumask = flush_cpumask();
 
 	flush_generation();
 
 	/* Update the list of reserved ASIDs and the ASID bitmap. */
 	set_reserved_asid_bits();
 
-	for_each_possible_cpu(i) {
+	for_each_cpu(i, cpumask) {
 		asid = atomic64_xchg_relaxed(&per_cpu(active_asids, i), 0);
 		/*
 		 * If this CPU has already been through a
@@ -158,7 +166,7 @@ static void flush_context(void)
 	 * Queue a TLB invalidation for each CPU to perform on next
 	 * context-switch
 	 */
-	cpumask_setall(&tlb_flush_pending);
+	cpumask_or(&tlb_flush_pending, &tlb_flush_pending, cpumask);
 }
 
 static bool check_update_reserved_asid(u64 asid, u64 newasid)
@@ -439,6 +447,8 @@ static int asids_init(void)
 	pinned_asid.map = bitmap_zalloc(NUM_USER_ASIDS, GFP_KERNEL);
 	pinned_asid.nr = 0;
 
+	asid_housekeeping_mask = cpu_possible_mask;
+
 	/*
 	 * We cannot call set_reserved_asid_bits() here because CPU
 	 * caps are not finalized yet, so it is safer to assume KPTI
-- 
2.27.0