[PATCH 7/8] riscv: improve the local flushing logic in sys_riscv_flush_icache

[Christoph Hellwig <hch@lst.de>]

If we have to offload any remote sfence the SBI we might as well let it
handle the local one as well.  This significantly simplifies the cpumask
operations and streamlines the code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/mm/cacheflush.c | 33 ++++++++++++++-------------------
 1 file changed, 14 insertions(+), 19 deletions(-)

diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 9180b2e93058..8f1134715fec 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -20,7 +20,6 @@ void flush_icache_all(void)
 static void flush_icache_mm(bool local)
 {
 	unsigned int cpu = get_cpu();
-	cpumask_t others, hmask;
 
 	/*
 	 * Mark the I$ for all harts not concurrently executing as needing a
@@ -29,27 +28,23 @@ static void flush_icache_mm(bool local)
 	cpumask_andnot(&current->mm->context.icache_stale_mask,
 		       cpu_possible_mask, mm_cpumask(current->mm));
 
-	/* Flush this hart's I$ now, and mark it as flushed. */
-	local_flush_icache_all();
-
 	/*
-	 * Flush the I$ of other harts concurrently executing.
+	 * It's assumed that at least one strongly ordered operation is
+	 * performed on this hart between setting a hart's cpumask bit and
+	 * scheduling this MM context on that hart.  Sending an SBI remote
+	 * message will do this, but in the case where no messages are sent we
+	 * still need to order this hart's writes with flush_icache_deferred().
 	 */
-	cpumask_andnot(&others, mm_cpumask(current->mm), cpumask_of(cpu));
-	local |= cpumask_empty(&others);
-	if (!local) {
-		riscv_cpuid_to_hartid_mask(&others, &hmask);
-		sbi_remote_fence_i(hmask.bits);
-	} else {
-		/*
-		 * It's assumed that at least one strongly ordered operation is
-		 * performed on this hart between setting a hart's cpumask bit
-		 * and scheduling this MM context on that hart.  Sending an SBI
-		 * remote message will do this, but in the case where no
-		 * messages are sent we still need to order this hart's writes
-		 * with flush_icache_deferred().
-		 */
+	cpu = get_cpu();
+	if (local ||
+	    cpumask_any_but(mm_cpumask(current->mm), cpu) >= nr_cpu_ids) {
+		local_flush_icache_all();
 		smp_mb();
+	} else {
+		cpumask_t hmask;
+
+		riscv_cpuid_to_hartid_mask(mm_cpumask(current->mm), &hmask);
+		sbi_remote_fence_i(cpumask_bits(&hmask));
 	}
 
 	put_cpu();
-- 
2.20.1


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