Re: Question on kzalloc and GFP_DMA32
From: David Rientjes
Date: Wed Sep 28 2016 - 17:11:51 EST
On Tue, 27 Sep 2016, Ben Greear wrote:
> 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
> 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
> below, especially with several NICs in the system.
I suppose it's failing sometimes because the BUG() will trigger when
trying to allocate new slab or CONFIG_ZONE_DMA32 isn't configured. That
shouldn't panic the kernel anymore since commit 72baeef0c271 ("slab: do
not panic on invalid gfp_mask") in 4.8, but you shouldn't be doing
kzalloc(..., ... | GFP_DMA32) anyway.
> pool_size is relatively large (maybe 256k or so).
If it's 256k, why allocate through the slab allocator? Why not
alloc_pages(GFP_KERNEL | GFP_DMA32 | __GFP_ZERO | __GFP_NOWARN,