Re: [PATCH v24 5/9] arm64: kdump: add kdump support

[James Morse <james.morse@arm.com>]

On 19/08/16 02:26, AKASHI Takahiro wrote:
> Can you try the following change?
> If it fixes your problem, I will post it as a patch.

Almost! This causes booting with acpi=on to fail for the familiar
alignment-fault reasons[2],
details and a suggested fix below.

I think we should have this change as it matches x86's use of acpi, and means we
don't rely on re-parsing the efi memory map to learn which areas of memory
shouldn't be in the vmcore.


> ===8<===
> From 740563e4a437f0d6ecf6e421c91433f9b8f19041 Mon Sep 17 00:00:00 2001
> From: AKASHI Takahiro <takahiro.akashi@linaro.org>
> Date: Fri, 19 Aug 2016 09:57:52 +0900
> Subject: [PATCH] arm64: mark reserved memblock regions explicitly
> 
> ---
>  arch/arm64/kernel/setup.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 38eda13..38589b5 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -205,10 +205,15 @@ static void __init request_standard_resources(void)
>  
>  	for_each_memblock(memory, region) {
>  		res = alloc_bootmem_low(sizeof(*res));
> -		res->name  = "System RAM";
> +		if (memblock_is_nomap(region)) {
> +			res->name  = "reserved";

> +			res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;

This causes acpica to choke.  arch/arm64/include/asm/acpi.h:acpi_os_ioremap()
calls page_is_ram(), which expects IORESOURCE_SYSTEM_RAM. From kernel/resource.c:
> /*
>  * This generic page_is_ram() returns true if specified address is
>  * registered as System RAM in iomem_resource list.
>  */
> int __weak page_is_ram(unsigned long pfn)

We are trying to infer information about the EFI memory map by looking through
iomem_resource list generated from memblock.
drivers/firmware/efi/arm-init.c:reserve_regions() adds memory with the WB
attribute to memblock via early_init_dt_add_memory_arch(), so changing
page_is_ram() for memblock_is_memory() is one step closer to checking the
attributes in the efi memory map (which turns out to tricky).

With your v24 on v4.8-rc1 and 'mark reserved memblock regions explicitly', and
this extra hack [0], I can boot, kdump, extract the vmcore (with read() and
mmap()), and pull things out of it with crash.


Thanks,

James


> +		} else {
> +			res->name  = "System RAM";
> +			res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> +		}
>  		res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
>  		res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
> -		res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
>  
>  		request_resource(&iomem_resource, res);

[0] whitespace damaged hack for acpi_os_ioremap().
------------------------------------%<------------------------------------
+++ b/arch/arm64/include/asm/acpi.h
@@ -12,6 +12,7 @@
 #ifndef _ASM_ACPI_H
 #define _ASM_ACPI_H

+#include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/psci.h>

@@ -32,7 +33,11 @@
 static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
                                            acpi_size size)
 {
-       if (!page_is_ram(phys >> PAGE_SHIFT))
+       /*
+        * EFI's reserve_regions() call adds memory with the WB attribute
+        * to memblock via early_init_dt_add_memory_arch().
+        */
+       if (!memblock_is_memory(phys))
                return ioremap(phys, size);

        return ioremap_cache(phys, size);
------------------------------------%<------------------------------------

[1] cat /proc/iomem | tail -n 9
8000000000-8001e7ffff : reserved
8001e80000-83ff17ffff : System RAM
  8002080000-8002b0ffff : Kernel code
  8002d90000-8002f6ffff : Kernel data
  80dfe00000-80ffdfffff : Crash kernel
83ff180000-83ff1cffff : reserved
83ff1d0000-83ff21ffff : System RAM
83ff220000-83ffe4ffff : reserved
83ffe50000-83ffffffff : System RAM

[2] Panic on boot without [0]
[    0.037098] ACPI: Core revision 20160422
[    0.041174] Unable to handle kernel paging request at virtual address
fffffc0008f831e7
[    0.049155] pgd = fffffc0008f50000
[    0.052576] [fffffc0008f831e7] *pgd=00000083fffe0003, *pud=00000083fffe0003,
*pmd=00000083fffe0003, *pte=00e80083ff1c0707
[    0.063632] Internal error: Oops: 96000021 [#1] PREEMPT SMP
[    0.069245] Modules linked in:
[    0.072317] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.8.0-rc1+ #4892
[    0.078891] Hardware name: AMD Seattle (Rev.B0) Development Board (Overdrive)
(DT)
[    0.086518] task: fffffc0008dc8a80 task.stack: fffffc0008d90000
[    0.092486] PC is at acpi_ns_lookup+0x238/0x378
[    0.097049] LR is at acpi_ds_load1_begin_op+0x88/0x260
[    0.102290] pc : [<fffffc000840fed8>] lr : [<fffffc0008405dcc>] pstate: 60000045
[    0.109740] sp : fffffc0008d93bb0
[    0.113071] x29: fffffc0008d93bb0 x28: 0000000000000001
[    0.118420] x27: 0000000000000000 x26: 000000000000001b
[    0.123768] x25: fffffc0008a813b7 x24: 000000000000001b
[    0.129119] x23: 000000000000001b x22: 0000000000000001
[    0.134466] x21: fffffc0008d93cb8 x20: 0000000000000001
[    0.139814] x19: fffffc0008f831e7 x18: 0000000000000023
[    0.145163] x17: ffffffffffffffff x16: 0000000000000000
[    0.150511] x15: 000000000000038e x14: 0000000000007fff
[    0.155859] x13: ffffffffffffff00 x12: 0000000000000008
[    0.161208] x11: 0000000000000028 x10: 00000000ffffff76
[    0.166556] x9 : 0000000000000000 x8 : fffffe03c00b0140
[    0.171907] x7 : 0000000000000003 x6 : fffffc0008d93cb8
[    0.177255] x5 : fffffe03c0060800 x4 : fffffc0008ee7fe8
[    0.182603] x3 : fffffc0008ee8000 x2 : fffffc0008ee7fe8
[    0.187951] x1 : fffffc0008f831e7 x0 : 0000000000000000
[    0.193296]
[    0.194789] Process swapper/0 (pid: 0, stack limit = 0xfffffc0008d90020)
[    0.483605] Call trace:
[    0.486062] Exception stack(0xfffffc0008d939e0 to 0xfffffc0008d93b10)
[    0.568522] [<fffffc000840fed8>] acpi_ns_lookup+0x238/0x378
[    0.574134] [<fffffc0008405dcc>] acpi_ds_load1_begin_op+0x88/0x260
[    0.580358] [<fffffc0008415e3c>] acpi_ps_build_named_op+0xa8/0x170
[    0.586582] [<fffffc0008416034>] acpi_ps_create_op+0x130/0x230
[    0.592455] [<fffffc0008415988>] acpi_ps_parse_loop+0x174/0x580
[    0.598419] [<fffffc00084168b4>] acpi_ps_parse_aml+0xa8/0x278
[    0.604208] [<fffffc0008411efc>] acpi_ns_one_complete_parse+0x130/0x158
[    0.610871] [<fffffc0008411f48>] acpi_ns_parse_table+0x24/0x44
[    0.616745] [<fffffc00084116fc>] acpi_ns_load_table+0x50/0xe0
[    0.622535] [<fffffc000841ad80>] acpi_tb_load_namespace+0xdc/0x25c
[    0.628764] [<fffffc0008b383f4>] acpi_load_tables+0x3c/0xa8
[    0.634377] [<fffffc0008b37548>] acpi_early_init+0x88/0xbc
[    0.639903] [<fffffc0008b10b30>] start_kernel+0x330/0x394
[    0.645340] [<fffffc0008b10210>] __primary_switched+0x7c/0x8c
[    0.651127] Code: 2a1a03f7 2a0002d6 36380054 321902d6 (b9400260)
[    0.657270] ---[ end trace 0000000000000000 ]---
[    0.661922] Kernel panic - not syncing: Attempted to kill the idle task!
[    0.668673] ---[ end Kernel panic - not syncing: Attempted to kill the idle task!


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