riscv: don't probe unaligned access speed if already done

[ Upstream commit c20d36cc2a2073d4cdcda92bd7a1bb9b3b3b7c79 ]

If misaligned_access_speed percpu var isn't so called "HWPROBE
MISALIGNED UNKNOWN", it means the probe has happened(this is possible
for example, hotplug off then hotplug on one cpu), and the percpu var
has been set, don't probe again in this case.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Fixes: 584ea6564bca ("RISC-V: Probe for unaligned access speed")
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230912154040.3306-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 1cfbba6..e12cd22 100644 (file)
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -568,6 +568,10 @@ void check_unaligned_access(int cpu)
        void *src;
        long speed = RISCV_HWPROBE_MISALIGNED_SLOW;
 
+       /* We are already set since the last check */
+       if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_UNKNOWN)
+               return;
+
        page = alloc_pages(GFP_NOWAIT, get_order(MISALIGNED_BUFFER_SIZE));
        if (!page) {
                pr_warn("Can't alloc pages to measure memcpy performance");