From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754904AbcI1Xhu (ORCPT ); Wed, 28 Sep 2016 19:37:50 -0400 Received: from mail2.candelatech.com ([208.74.158.173]:46686 "EHLO mail2.candelatech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752020AbcI1Xhj (ORCPT ); Wed, 28 Sep 2016 19:37:39 -0400 Subject: Re: Question on kzalloc and GFP_DMA32 To: David Rientjes References: <9b251303-2267-3f28-364e-031e92c79348@candelatech.com> Cc: linux-kernel@vger.kernel.org From: Ben Greear Organization: Candela Technologies Message-ID: Date: Wed, 28 Sep 2016 16:37:38 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/28/2016 02:11 PM, David Rientjes wrote: > 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 >> >> -------------------- 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. >> > > 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. CONFIG_ZONE_DMA32 is enabled in my .config. >> 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, > get_order(pool_size))? I really don't understand the (subtle?) difference between alloc_pages and kzalloc, but I will give your suggestion a try and see if it works. If you have time, maybe you could take a look at drivers/net/wireless/ath/ath10k/wmi.c in the ath10k_wmi_alloc_chunk method to see if you notice any problems with using alloc_pages there? Thanks for the suggestion. -- Ben Greear Candela Technologies Inc http://www.candelatech.com