Re: pci-usb/pci-sata broken with LPAE config after "reduce use of block bounce buffers"

From: Kishon Vijay Abraham I <kishon@ti.com>
To: Christoph Hellwig <hch@lst.de>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
Subject: Re: pci-usb/pci-sata broken with LPAE config after "reduce use of block bounce buffers"
Date: Wed, 5 Feb 2020 10:45:24 +0530	[thread overview]
Message-ID: <a5eb4f73-418a-6780-354f-175d08395e71@ti.com> (raw)
In-Reply-To: <20200203142155.GA16388@lst.de>

Hi Christoph,

On 03/02/20 7:51 PM, Christoph Hellwig wrote:
> On Fri, Jan 31, 2020 at 05:14:01PM +0530, Kishon Vijay Abraham I wrote:
>>> Can you throw in a little debug printk if this comes from
>>> dma_direct_possible or swiotlb_map?
>>
>> I could see swiotlb_tbl_map_single() returning DMA_MAPPING_ERROR.
>>
>> Kernel with debug print:
>> https://github.com/kishon/linux-wip.git nvm_dma_issue
>>
>> Full log: https://pastebin.ubuntu.com/p/Xf2ngxc3kB/
> 
> Ok, this mostly like means we allocate a swiotlb buffer that isn't
> actually addressable.  To verify that can you post the output with the
> first attached patch?  If it shows the overflow message added there,
> please try if the second patch fixes it.

I'm seeing some sort of busy loop after applying your 1st patch. I sent
a SysRq to see where it is stuck

[  182.641398] sysrq: Show Blocked State
[  182.645080]   task                PC stack   pid father
[  182.650359] sync            D    0  2101   1901 0x00000000
[  182.655889] [<c0a399b8>] (__schedule) from [<c0a39e54>]
(schedule+0xa0/0x138)
[  182.663063] [<c0a39e54>] (schedule) from [<c0a3a484>]
(io_schedule+0x14/0x34)
[  182.670237] [<c0a3a484>] (io_schedule) from [<c02eebec>]
(wait_on_page_bit+0x14c/0x1a8)
[  182.678283] [<c02eebec>] (wait_on_page_bit) from [<c02edaa4>]
(__filemap_fdatawait_range+0x94/0xec)
[  182.687374] [<c02edaa4>] (__filemap_fdatawait_range) from
[<c02edb8c>] (filemap_fdatawait_keep_errors+0x24/0x50)
[  182.697601] [<c02edb8c>] (filemap_fdatawait_keep_errors) from
[<c0385a84>] (sync_inodes_sb+0x1a8/0x23c)
[  182.707041] [<c0385a84>] (sync_inodes_sb) from [<c035bd84>]
(iterate_supers+0x88/0xdc)
[  182.714998] [<c035bd84>] (iterate_supers) from [<c0389be4>]
(ksys_sync+0x40/0xb8)
[  182.722519] [<c0389be4>] (ksys_sync) from [<c0389c64>]
(sys_sync+0x8/0x10)
[  182.729429] [<c0389c64>] (sys_sync) from [<c0201000>]
(ret_fast_syscall+0x0/0x4c)
[  182.736943] Exception stack(0xe5461fa8 to 0xe5461ff0)
[  182.742016] 1fa0:                   be8a8db4 be8a8db8 00000000
ffffffff 00000000 0009d6b8
[  182.750230] 1fc0: be8a8db4 be8a8db8 00000001 00000024 be8a8db4
00000000 b6f0b000 0009d6dc
[  182.758443] 1fe0: b6e2e3d0 be8a8c1c 00064821 b6e2e3dc

Full log here: https://pastebin.ubuntu.com/p/q6yDtP9vxR/

Thanks
Kishon
> 