Re: [PATCH 2/3] arm64: acpi,efi: fix alignment fault in accessing ACPI tables at kdump

[AKASHI Takahiro <takahiro.akashi@linaro.org>]

James,

On Fri, Jun 15, 2018 at 05:30:08PM +0100, James Morse wrote:
> Hi Akashi,
> 
> On 15/06/18 08:56, AKASHI Takahiro wrote:
> > This is a fix against the issue that crash dump kernel may hang up
> > during booting, which can happen on any ACPI-based system with "ACPI
> > Reclaim Memory."
> > 
> > (kernel messages after panic kicked off kdump)
> > 	   (snip...)
> > 	Bye!
> > 	   (snip...)
> > 	ACPI: Core revision 20170728
> > 	pud=000000002e7d0003, *pmd=000000002e7c0003, *pte=00e8000039710707
> > 	Internal error: Oops: 96000021 [#1] SMP
> > 	Modules linked in:
> > 	CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.14.0-rc6 #1
> > 	task: ffff000008d05180 task.stack: ffff000008cc0000
> > 	PC is at acpi_ns_lookup+0x25c/0x3c0
> > 	LR is at acpi_ds_load1_begin_op+0xa4/0x294
> > 	   (snip...)
> > 	Process swapper/0 (pid: 0, stack limit = 0xffff000008cc0000)
> > 	Call trace:
> > 	   (snip...)
> > 	[<ffff0000084a6764>] acpi_ns_lookup+0x25c/0x3c0
> > 	[<ffff00000849b4f8>] acpi_ds_load1_begin_op+0xa4/0x294
> > 	[<ffff0000084ad4ac>] acpi_ps_build_named_op+0xc4/0x198
> > 	[<ffff0000084ad6cc>] acpi_ps_create_op+0x14c/0x270
> > 	[<ffff0000084acfa8>] acpi_ps_parse_loop+0x188/0x5c8
> > 	[<ffff0000084ae048>] acpi_ps_parse_aml+0xb0/0x2b8
> > 	[<ffff0000084a8e10>] acpi_ns_one_complete_parse+0x144/0x184
> > 	[<ffff0000084a8e98>] acpi_ns_parse_table+0x48/0x68
> > 	[<ffff0000084a82cc>] acpi_ns_load_table+0x4c/0xdc
> > 	[<ffff0000084b32f8>] acpi_tb_load_namespace+0xe4/0x264
> > 	[<ffff000008baf9b4>] acpi_load_tables+0x48/0xc0
> > 	[<ffff000008badc20>] acpi_early_init+0x9c/0xd0
> > 	[<ffff000008b70d50>] start_kernel+0x3b4/0x43c
> > 	Code: b9008fb9 2a000318 36380054 32190318 (b94002c0)
> > 	---[ end trace c46ed37f9651c58e ]---
> > 	Kernel panic - not syncing: Fatal exception
> > 	Rebooting in 10 seconds..
> > 
> > (diagnosis)
> > * This fault is a data abort, alignment fault (ESR=0x96000021)
> >   during reading out ACPI table.
> > * Initial ACPI tables are normally stored in system ram and marked as
> >   "ACPI Reclaim memory" by the firmware.
> > * After the commit f56ab9a5b73c ("efi/arm: Don't mark ACPI reclaim
> >   memory as MEMBLOCK_NOMAP"), those regions are differently handled
> >   as they are "memblock-reserved", without NOMAP bit.
> > * So they are now excluded from device tree's "usable-memory-range"
> >   which kexec-tools determines based on a current view of /proc/iomem.
> > * When crash dump kernel boots up, it tries to accesses ACPI tables by
> >   mapping them with ioremap(), not ioremap_cache(), in acpi_os_ioremap()
> >   since they are no longer part of mapped system ram.
> > * Given that ACPI accessor/helper functions are compiled in without
> >   unaligned access support (ACPI_MISALIGNMENT_NOT_SUPPORTED),
> >   any unaligned access to ACPI tables can cause a fatal panic.
> > 
> > With this patch, acpi_os_ioremap() always honors memory attribute
> > information provided by the firmware (EFI) and retaining cacheability
> > allows the kernel safe access to ACPI tables.
> 
> 
> > Please note that arm_enable_runtime_services() is now renamed to
> > efi_enter_virtual_mode() due to the similarity to x86's.
> 
> Just a rename?:

and maps EFI memory map whether or not runtime service is enabled.

> >  drivers/firmware/efi/arm-runtime.c | 27 ++++++++++++---------------
> 
> 
> 
> > diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> > index 32f465a80e4e..d53c95f4e1a9 100644
> > --- a/arch/arm64/include/asm/acpi.h
> > +++ b/arch/arm64/include/asm/acpi.h
> > @@ -29,18 +31,22 @@
> >  
> >  /* Basic configuration for ACPI */
> >  #ifdef	CONFIG_ACPI
> > +pgprot_t __acpi_get_mem_attribute(phys_addr_t addr);
> > +
> >  /* ACPI table mapping after acpi_permanent_mmap is set */
> >  static inline void __iomem *acpi_os_ioremap(acpi_physical_address phys,
> >  					    acpi_size size)
> >  {
> > +	/* For normal memory we already have a cacheable mapping. */
> > +	if (memblock_is_map_memory(phys))
> > +		return (void __iomem *)__phys_to_virt(phys);
> 
> >  	/*
> > -	 * EFI's reserve_regions() call adds memory with the WB attribute
> > -	 * to memblock via early_init_dt_add_memory_arch().
> > +	 * We should still honor the memory's attribute here because
> > +	 * crash dump kernel possibly excludes some ACPI (reclaim)
> > +	 * regions from memblock list.
> >  	 */
> 
> (Even without kdump we would still need this. Regions ACPI wants mapped may not
> be covered by the linear map. In this case we need to use the attributes
> firmware described in the UEFI memory map. Kdump exacerbates this by
> artificially reducing the range of the linear map.)
> 
> 
> > -	if (!memblock_is_memory(phys))
> > -		return ioremap(phys, size);
> > -
> > -	return ioremap_cache(phys, size);
> > +	return __ioremap(phys, size, __acpi_get_mem_attribute(phys));
> >  }
> 
> 
> 
> > diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
> > index 5889cbea60b8..566ef0a9edb5 100644
> > --- a/drivers/firmware/efi/arm-runtime.c
> > +++ b/drivers/firmware/efi/arm-runtime.c
> > @@ -106,46 +106,43 @@ static bool __init efi_virtmap_init(void)
> >   * non-early mapping of the UEFI system table and virtual mappings for all
> >   * EFI_MEMORY_RUNTIME regions.
> >   */
> > -static int __init arm_enable_runtime_services(void)
> > +void __init efi_enter_virtual_mode(void)
> >  {
> >  	u64 mapsize;
> >  
> >  	if (!efi_enabled(EFI_BOOT)) {
> >  		pr_info("EFI services will not be available.\n");
> > -		return 0;
> > +		return;
> > +	}
> > +
> > +	mapsize = efi.memmap.desc_size * efi.memmap.nr_map;
> > +
> > +	if (efi_memmap_init_late(efi.memmap.phys_map, mapsize)) {
> > +		pr_err("Failed to remap EFI memory map\n");
> > +		return;
> >  	}
> >  
> >  	if (efi_runtime_disabled()) {
> >  		pr_info("EFI runtime services will be disabled.\n");
> > -		return 0;
> > +		return;
> >  	}
> >  
> >  	if (efi_enabled(EFI_RUNTIME_SERVICES)) {
> >  		pr_info("EFI runtime services access via paravirt.\n");
> > -		return 0;
> > +		return;
> >  	}
> >  
> >  	pr_info("Remapping and enabling EFI services.\n");
> >  
> > -	mapsize = efi.memmap.desc_size * efi.memmap.nr_map;
> > -
> > -	if (efi_memmap_init_late(efi.memmap.phys_map, mapsize)) {
> > -		pr_err("Failed to remap EFI memory map\n");
> > -		return -ENOMEM;
> > -	}
> > -
> >  	if (!efi_virtmap_init()) {
> >  		pr_err("UEFI virtual mapping missing or invalid -- runtime services will not be available\n");
> > -		return -ENOMEM;
> > +		return;
> >  	}
> >  
> >  	/* Set up runtime services function pointers */
> >  	efi_native_runtime_setup();
> >  	set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
> > -
> > -	return 0;
> >  }
> 
> Please have the drivers/firmware/efi/arm-runtime.c changes in a separate patch
> (maybe combine it with patch 3). The 'efi/arm: ' prefix is more likely to catch
> the maintainers attention.
>
> I think this is what Ard meant by:
> | Could you please move the changes to this file and init/main.c into a
> | separate patch?
> 
> https://patchwork.kernel.org/patch/10361761/
> 
> 
> > -early_initcall(arm_enable_runtime_services);
> 
> With just this patch, surely nothing ever calls arm_enable_runtime_services(),
> and now acpi_os_ioremap() will return device memory for anything that isn't part
> of the linear region. (This breaks RAS).

Actually I noticed the issue.

> This will make it difficult to bisect through for any RAS or
> efi-runtime-services issue. Its easily fixed: please put the efi+init changes in
> a patch before the acpi_os_ioremap() changes.

I was reluctant to put different part of code changes into one.
But if nobody cares, I will do so in three patches.
  * change arm_enable_runtime_services() with renaming
  * move this function earlier in start_kernel()
  * modify acpi_os_ioremap()

Thanks,
-Takahiro AKASHI


> Otherwise, looks good to me!
> 
> 
> Thanks,
> 
> James