4.19-rcX: WARN_ON() arch/arm64/kernel/setup.c:271 reserve_memblock_reserved_regions

4.19-rcX: WARN_ON() arch/arm64/kernel/setup.c:271 reserve_memblock_reserved_regions

[Paolo Pisati]

This on my dragonboard 410c:

...
[    0.170657] WARNING: CPU: 2 PID: 1 at arch/arm64/kernel/setup.c:271 reserve_memblock_reserved_regions+0xd4/0x150
[    0.170666] Modules linked in:
[    0.170680] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.19.0-rc7-dirty #3
[    0.170687] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
[    0.170696] pstate: 20000005 (nzCv daif -PAN -UAO)
[    0.170707] pc : reserve_memblock_reserved_regions+0xd4/0x150
[    0.170718] lr : reserve_memblock_reserved_regions+0xcc/0x150
[    0.170725] sp : ffff000008033d30
[    0.170731] x29: ffff000008033d30 x28: ffff000009048050
[    0.170744] x27: ffff000009048078 x26: ffff000008f871b0
[    0.170755] x25: 0000000000000000 x24: 0000000000488020
[    0.170767] x23: 00000000bfffffff x22: ffff000008f3ca28
[    0.170778] x21: ffff000008e61840 x20: ffff0000090e9000
[    0.170789] x19: ffff80003a218e00 x18: 0000000000000000
[    0.170800] x17: 0000000000000000 x16: 0000000000000000
[    0.170811] x15: 0000000000000000 x14: 0000000000000400
[    0.170822] x13: 0000000000000000 x12: 0000000000000028
[    0.170833] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f
[    0.170844] x9 : 0000000000000000 x8 : ffff80003a218e80
[    0.170855] x7 : 0000000000000000 x6 : ffff80003d9ffc70
[    0.170866] x5 : 0000000000000000 x4 : 00000000bfffffff
[    0.170877] x3 : 00000000bff00000 x2 : 0000000000000000
[    0.170888] x1 : ffff800009ff0000 x0 : 0000000000000000
[    0.170899] Call trace:
[    0.170910]  reserve_memblock_reserved_regions+0xd4/0x150
[    0.170921]  do_one_initcall+0x58/0x170
[    0.170931]  kernel_init_freeable+0x1a4/0x264
[    0.170942]  kernel_init+0x10/0x108
[    0.170952]  ret_from_fork+0x10/0x18
[    0.170962] ---[ end trace c7ce9242331f7319 ]---
[    0.170974] name: reserved res: [mem 0xbff00000-0xbfffffff flags 0x200]
...

that memory region corresponds to the ramoops node:

        reserved-memory {
                ramoops@bff00000{
                        compatible = "ramoops";
                        reg = <0x0 0xbff00000 0x0 0x100000>;

                        record-size = <0x20000>;
                        console-size = <0x20000>;
                        ftrace-size = <0x20000>;
                };
        };

According to the comment in reserve_memblock_reserved_regions():

               /*
                 * We expected memblock_reserve() regions to conflict with
                 * memory created by request_standard_resources().
                 */

and the reserved-memory region evades this condition, but i'm not entirely sure how to
properly fix this - any idea?
-- 
bye,
p.

Re: 4.19-rcX: WARN_ON() arch/arm64/kernel/setup.c:271 reserve_memblock_reserved_regions

[James Morse]

Hi Paolo!

On 08/10/2018 16:11, Paolo Pisati wrote:
> This on my dragonboard 410c:
> 
> ...
> [    0.170657] WARNING: CPU: 2 PID: 1 at arch/arm64/kernel/setup.c:271 reserve_memblock_reserved_regions+0xd4/0x150
> [    0.170666] Modules linked in:
> [    0.170680] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.19.0-rc7-dirty #3
> [    0.170687] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
> [    0.170696] pstate: 20000005 (nzCv daif -PAN -UAO)
> [    0.170707] pc : reserve_memblock_reserved_regions+0xd4/0x150
> [    0.170718] lr : reserve_memblock_reserved_regions+0xcc/0x150
> [    0.170725] sp : ffff000008033d30

> [    0.170899] Call trace:
> [    0.170910]  reserve_memblock_reserved_regions+0xd4/0x150
> [    0.170921]  do_one_initcall+0x58/0x170
> [    0.170931]  kernel_init_freeable+0x1a4/0x264
> [    0.170942]  kernel_init+0x10/0x108
> [    0.170952]  ret_from_fork+0x10/0x18
> [    0.170962] ---[ end trace c7ce9242331f7319 ]---
> [    0.170974] name: reserved res: [mem 0xbff00000-0xbfffffff flags 0x200]

John Stultz saw this on Hikey,

> that memory region corresponds to the ramoops node:

... it was the ramoops description too.

There is a patch:
https://www.spinics.net/lists/arm-kernel/msg675580.html

Which I need to re-spin.

This is happening because your reserved-memory isn't described as memory. I
mistakenly believed no-one would do this, and I really didn't want to walk both
them memory and reserved lists at the same time!

mm/page_alloc.c:zero_resv_unavail() has a comment about this:
|	* Once memblock is changed so such behaviour is not allowed: i.e.
|	* list of "reserved" memory must be a subset of list of "memory", then
|	* this code can be removed.


> According to the comment in reserve_memblock_reserved_regions():

> and the reserved-memory region evades this condition, but i'm not entirely sure how to
> properly fix this - any idea?

Ideally reserved-memory would be described as memory. If you need it to be
removed from the linear map (e.g. because it needs special memory attributes),
use the binding's 'nomap' property. This causes
early_init_dt_reserve_memory_arch() to remove the memory instead of marking it
reserved.

But! DT's that have this reserved-but-not-memory are already out there, so we
should work around this in the kernel.


Thanks,

James

Re: 4.19-rcX: WARN_ON() arch/arm64/kernel/setup.c:271 reserve_memblock_reserved_regions

[Paolo Pisati]

On Mon, Oct 08, 2018 at 05:03:27PM +0100, James Morse wrote:

> But! DT's that have this reserved-but-not-memory are already out there, so we
> should work around this in the kernel.

Ack, thanks for the explanation.
-- 
bye,
p.