Question on kzalloc and GFP_DMA32

[Ben Greear]

I have been running this patch for a while:

    ath10k:  Use GPF_DMA32 for firmware swap memory.

    This fixes OS crash when using QCA 9984 NIC on x86-64 system
    without vt-d enabled.

    Also tested on ea8500 with 9980, and x86-64 with 9980 and 9880.

    All tests were with CT firmware.

    Signed-off-by: Ben Greear <greearb@xxxxxxxxxxxxxxx>

-------------------- drivers/net/wireless/ath/ath10k/wmi.c --------------------
index e20aa39..727b3aa 100644
@@ -4491,7 +4491,7 @@ static int ath10k_wmi_alloc_chunk(struct ath10k *ar, u32 req_id,
         if (!pool_size)
             return -EINVAL;

-        vaddr = kzalloc(pool_size, GFP_KERNEL | __GFP_NOWARN);
+        vaddr = kzalloc(pool_size, GFP_KERNEL | __GFP_NOWARN | GFP_DMA32);
         if (!vaddr)
             num_units /= 2;
     }


It sometimes works, on some systems, but then it also often fails with the splat
below, especially with several NICs in the system.

pool_size is relatively large (maybe 256k or so).

Any idea for a more proper way to do this?


gfp: 4
------------[ cut here ]------------
kernel BUG at /home/greearb/git/linux-4.7.dev.y/mm/slub.c:1508!
invalid opcode: 0000 [#1] PREEMPT SMP
Modules linked in: coretemp hwmon ath9k intel_rapl ath10k_pci x86_pkg_temp_thermal ath9k_common ath10k_core intel_powerclamp ath9k_hw ath kvm iTCO_wdt mac80211 
iTCO_vendor_support irqbypass snd_hda_codec_hdmi 6
CPU: 2 PID: 268 Comm: kworker/u8:5 Not tainted 4.7.2+ #16
Hardware name: To be filled by O.E.M. To be filled by O.E.M./ChiefRiver, BIOS 4.6.5 06/07/2013
Workqueue: ath10k_aux_wq ath10k_wmi_event_service_ready_work [ath10k_core]
task: ffff880036433a00 ti: ffff880036440000 task.ti: ffff880036440000
RIP: 0010:[<ffffffff8124592a>]  [<ffffffff8124592a>] new_slab+0x39a/0x410
RSP: 0018:ffff880036443b58  EFLAGS: 00010092
RAX: 0000000000000006 RBX: 00000000024082c4 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffff88021e30dd08 RDI: ffff88021e30dd08
RBP: ffff880036443b90 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000372 R12: ffff88021dc01200
R13: ffff88021dc00cc0 R14: ffff88021dc01200 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88021e300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3e65c1c730 CR3: 0000000001e06000 CR4: 00000000001406e0
Stack:
 ffffffff8127a4fc ffff0a01ffffff10 00000000024082c4 ffff88021dc01200
 ffff88021dc00cc0 ffff88021dc01200 0000000000000001 ffff880036443c58
 ffffffff81247ac6 ffff88021e31b360 ffff880036433a00 ffff880036433a00
Call Trace:
 [<ffffffff8127a4fc>] ? __d_lookup+0x9c/0x160
 [<ffffffff81247ac6>] ___slab_alloc+0x396/0x4a0
 [<ffffffffa0f8e14d>] ? ath10k_wmi_event_service_ready_work+0x5ad/0x800 [ath10k_core]
 [<ffffffff811f5279>] ? alloc_kmem_pages+0x9/0x10
 [<ffffffff8120f203>] ? kmalloc_order+0x13/0x40
 [<ffffffffa0f8e14d>] ? ath10k_wmi_event_service_ready_work+0x5ad/0x800 [ath10k_core]
 [<ffffffff81247bf6>] __slab_alloc.isra.72+0x26/0x40
 [<ffffffff81248767>] __kmalloc+0x147/0x1b0
 [<ffffffffa0f8e14d>] ath10k_wmi_event_service_ready_work+0x5ad/0x800 [ath10k_core]
 [<ffffffff811370a1>] ? dequeue_entity+0x261/0xac0
 [<ffffffff8111c2d8>] process_one_work+0x148/0x420
 [<ffffffff8111c929>] worker_thread+0x49/0x480
 [<ffffffff8111c8e0>] ? rescuer_thread+0x330/0x330
 [<ffffffff81121984>] kthread+0xc4/0xe0
 [<ffffffff8184d75f>] ret_from_fork+0x1f/0x40
 [<ffffffff811218c0>] ? kthread_create_on_node+0x170/0x170
Code: e9 65 fd ff ff 49 8b 57 20 48 8d 42 ff 83 e2 01 49 0f 44 c7 f0 80 08 40 e9 6f fd ff ff 89 c6 48 c7 c7 01 36 c7 81 e8 e8 40 fa ff <0f> 0b ba 00 10 00 00 be 
5a 00 00 00 48 89 c7 48 d3 e2 e8 bf 18
RIP  [<ffffffff8124592a>] new_slab+0x39a/0x410
 RSP <ffff880036443b58>
---[ end trace ea3b0043b2911d93 ]---


static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
{
        if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
                pr_emerg("gfp: %u\n", flags & GFP_SLAB_BUG_MASK);
                BUG();
        }

        return allocate_slab(s,
                flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
}


Thanks,
Ben

--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com