From c8b00bb742dd036388f37d019dbb9db177f3e66c Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Thu, 1 Nov 2018 16:21:05 +1100 Subject: [PATCH] powerpc/mm/64s: Fix preempt warning in slb_allocate_kernel() With preempt enabled we see warnings in do_slb_fault(): BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u33:0/98 futex hash table entries: 4096 (order: 3, 524288 bytes) caller is do_slb_fault+0x204/0x230 CPU: 5 PID: 98 Comm: kworker/u33:0 Not tainted 4.19.0-rc3-gcc-7.3.1-00022-g1936f094e164 #138 Call Trace: dump_stack+0xb4/0x104 (unreliable) check_preemption_disabled+0x148/0x150 do_slb_fault+0x204/0x230 data_access_slb_common+0x138/0x180 This is caused by the get_paca() in slb_allocate_kernel(), which includes a call to debug_smp_processor_id(). slb_allocate_kernel() can only be called from do_slb_fault(), and in that path interrupts are hard disabled and so we can't be preempted, but we can't update the preempt flags (in thread_info) because that could cause an SLB fault. So just use local_paca which is safe and doesn't cause the warning. Fixes: 48e7b7695745 ("powerpc/64s/hash: Convert SLB miss handlers to C") Signed-off-by: Michael Ellerman --- arch/powerpc/mm/slb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c index b663a36f9ada..bc3914d54e26 100644 --- a/arch/powerpc/mm/slb.c +++ b/arch/powerpc/mm/slb.c @@ -708,7 +708,7 @@ static long slb_allocate_kernel(unsigned long ea, unsigned long id) return -EFAULT; if (ea < H_VMALLOC_END) - flags = get_paca()->vmalloc_sllp; + flags = local_paca->vmalloc_sllp; else flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_io_psize].sllp; } else { -- 2.30.2