On Wed, Jun 22, 2016 at 11:50:01AM +0100, Mark Rutland wrote:
> On Wed, Jun 22, 2016 at 06:24:31PM +0800, Dennis Chen wrote:
> > When kernel parameter 'mem=x' is specified by the command line,
> > probably the ACPI memory regions from firmware will beyond the
> > scope of the physical memory space after limited, if we don't add
> > back those regions into memblock in this case, then the ACPI core
> > will map it as device memory type. Since the ACPI core will produce
> > non-alignment access when parsing the AML data stream, alignment
> > exception will be generated upon the device memory mapped region.
> >
> > Below is an alignment exception output observed on ARM platform
> > with acpi enabled:
> > ...
> > [ 0.542475] Unable to handle kernel paging request at virtual address ffff0000080521e7
> > [ 0.550457] pgd = ffff000008aa0000
> > [ 0.553880] [ffff0000080521e7] *pgd=000000801fffe003, *pud=000000801fffd003, *pmd=000000801fffc003, *pte=00e80083ff1c1707
> > [ 0.564939] Internal error: Oops: 96000021 [#1] PREEMPT SMP
> > [ 0.570553] Modules linked in:
> > [ 0.573626] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.7.0-rc3-next-20160616+ #172
> > [ 0.581344] Hardware name: AMD Overdrive/Supercharger/Default string, BIOS ROD1001A 02/09/2016
> > [ 0.590025] task: ffff800001ef0000 ti: ffff800001ef8000 task.ti: ffff800001ef8000
> > [ 0.597571] PC is at acpi_ns_lookup+0x520/0x734
> > [ 0.602134] LR is at acpi_ns_lookup+0x4a4/0x734
> > [ 0.606693] pc : [<ffff0000083b8b10>] lr : [<ffff0000083b8a94>] pstate: 60000045
> > [ 0.614145] sp : ffff800001efb8b0
> > [ 0.617478] x29: ffff800001efb8c0 x28: 000000000000001b
> > [ 0.622829] x27: 0000000000000001 x26: 0000000000000000
> > [ 0.628181] x25: ffff800001efb9e8 x24: ffff000008a10000
> > [ 0.633531] x23: 0000000000000001 x22: 0000000000000001
> > [ 0.638881] x21: ffff000008724000 x20: 000000000000001b
> > [ 0.644230] x19: ffff0000080521e7 x18: 000000000000000d
> > [ 0.649580] x17: 00000000000038ff x16: 0000000000000002
> > [ 0.654929] x15: 0000000000000007 x14: 0000000000007fff
> > [ 0.660278] x13: ffffff0000000000 x12: 0000000000000018
> > [ 0.665627] x11: 000000001fffd200 x10: 00000000ffffff76
> > [ 0.670978] x9 : 000000000000005f x8 : ffff000008725fa8
> > [ 0.676328] x7 : ffff000008a8df70 x6 : ffff000008a8df70
> > [ 0.681679] x5 : ffff000008a8d000 x4 : 0000000000000010
> > [ 0.687027] x3 : 0000000000000010 x2 : 000000000000000c
> > [ 0.692378] x1 : 0000000000000006 x0 : 0000000000000000
> > ...
> > [ 1.262235] [<ffff0000083b8b10>] acpi_ns_lookup+0x520/0x734
> > [ 1.267845] [<ffff0000083a7160>] acpi_ds_load1_begin_op+0x174/0x4fc
> > [ 1.274156] [<ffff0000083c1f4c>] acpi_ps_build_named_op+0xf8/0x220
> > [ 1.280380] [<ffff0000083c227c>] acpi_ps_create_op+0x208/0x33c
> > [ 1.286254] [<ffff0000083c1820>] acpi_ps_parse_loop+0x204/0x838
> > [ 1.292215] [<ffff0000083c2fd4>] acpi_ps_parse_aml+0x1bc/0x42c
> > [ 1.298090] [<ffff0000083bc6e8>] acpi_ns_one_complete_parse+0x1e8/0x22c
> > [ 1.304753] [<ffff0000083bc7b8>] acpi_ns_parse_table+0x8c/0x128
> > [ 1.310716] [<ffff0000083bb8fc>] acpi_ns_load_table+0xc0/0x1e8
> > [ 1.316591] [<ffff0000083c9068>] acpi_tb_load_namespace+0xf8/0x2e8
> > [ 1.322818] [<ffff000008984128>] acpi_load_tables+0x7c/0x110
> > [ 1.328516] [<ffff000008982ea4>] acpi_init+0x90/0x2c0
> > [ 1.333603] [<ffff0000080819fc>] do_one_initcall+0x38/0x12c
> > [ 1.339215] [<ffff000008960cd4>] kernel_init_freeable+0x148/0x1ec
> > [ 1.345353] [<ffff0000086b7d30>] kernel_init+0x10/0xec
> > [ 1.350529] [<ffff000008084e10>] ret_from_fork+0x10/0x40
> > [ 1.355878] Code: b9009fbc 2a00037b 36380057 3219037b (b9400260)
> > [ 1.362035] ---[ end trace 03381e5eb0a24de4 ]---
> > [ 1.366691] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> >
> > With 'efi=debug', we can see those ACPI regions from firmware as:
> > [ 0.000000] efi: 0x0083ff1b5000-0x0083ff1c2fff [ACPI Reclaim Memory| | | | | | | | |WB|WT|WC|UC]*
> > [ 0.000000] efi: 0x0083ff223000-0x0083ff224fff [ACPI Memory NVS | | | | | | | | |WB|WT|WC|UC]*
> >
> > This patch is trying to add back those regions into memblock, make
> > ACPI core map it as normal memory instead of device memory type.
>
> I'm really not keen on this, as it only solves this particular instance
> of the problem (of losing the ability to identify addresses as being
> RAM). Also, it's not really an architecture-specific problem, so I'm not
> keen on this living under arch/arm64.
>
> I think we need a more fundamental rethink of the way we use memblock
> for this case.
>
> I would rather than we reworked memblock_enforce_memory_limit to mark
> items above the limit as nomap instead, which will preserve the ability
> to identify regions as memory while not using them for allocation and
> the linear map.
>
Hi Mark,
Thanks for the review and comments!I also think it's a good idea to mark
the memory regions that above the limit as NOMAP type memblock region, base
on this I'm trying to figure out a unify solution to fix this issue for both
DT and ACPI based path.
So I'll rework this patch and will sent it late once it's being finished.
Thanks,
Dennis
>
> > Signed-off-by: Dennis Chen <dennis.chen@xxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Steve Capper <steve.capper@xxxxxxx>
> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > Cc: Will Deacon <will.deacon@xxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
> > Cc: linux-acpi@xxxxxxxxxxxxxxx
> > Cc: linux-efi@xxxxxxxxxxxxxxx
> > ---
> > arch/arm64/include/asm/memblock.h | 14 +++++++++++++-
> > arch/arm64/kernel/acpi.c | 23 +++++++++++++++++++++++
> > arch/arm64/mm/init.c | 3 ++-
> > drivers/firmware/efi/arm-init.c | 19 +++++++++++++++++++
> > 4 files changed, 57 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/memblock.h b/arch/arm64/include/asm/memblock.h
> > index 6afeed2..8f2e887 100644
> > --- a/arch/arm64/include/asm/memblock.h
> > +++ b/arch/arm64/include/asm/memblock.h
> > @@ -16,6 +16,18 @@
> > #ifndef __ASM_MEMBLOCK_H
> > #define __ASM_MEMBLOCK_H
> >
> > -extern void arm64_memblock_init(void);
> > +#ifdef CONFIG_ACPI
> > +typedef struct {
> > + u64 base;
> > + u64 size;
> > + int resv;
> > +} efi_acpi_reg_t;
>
> This is basically a memblock_region.
>
> > +
> > +#define MAX_ACPI_REGS 4
> > +extern unsigned int nr_acpi_regs;
> > +extern efi_acpi_reg_t acpi_regs[MAX_ACPI_REGS];
> > +#endif
>
> Where did MAX_ACPI_REGS come from? I'm not aware of any specified limit
> on the number of regions you can have, so this feels arbitrary.
>
> > diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
> > index 3e4f1a4..5b92a8c 100644
> > --- a/arch/arm64/kernel/acpi.c
> > +++ b/arch/arm64/kernel/acpi.c
> > @@ -28,6 +28,7 @@
> > #include <asm/cputype.h>
> > #include <asm/cpu_ops.h>
> > #include <asm/smp_plat.h>
> > +#include <asm/memblock.h>
>
> Nit: please keep includes alphabetically ordered.
>
> > + /*
> > + * For the case of 'mem=x' kernel parameter specified by cmdline:
> > + * when ACPI parses raw AML data within the ACPI data region,
> > + * sometimes it will produce non-alignment memory access, in order
> > + * to make kernel avoid generating alignment fault in this case, we
> > + * need to add back the firmware ACPI memory region into memblock,
> > + * thus the ACPI core will map it as normal memory, otherwise ACPI
> > + * will map the region as device memory type which trigers alignment
> > + * exception.
> > + */
> > + if (!acpi_disabled && memory_limit != (phys_addr_t)ULLONG_MAX) {
> > + for (i = 0; i < nr_acpi_regs; i++) {
> > + memblock_add(acpi_regs[i].base, acpi_regs[i].size);
> > + /* MEMBLOCK_NOMAP maybe cleaned before, re-flag it */
> > + if (acpi_regs[i].resv)
> > + memblock_mark_nomap(acpi_regs[i].base,
> > + acpi_regs[i].size);
>
> If it wasn't reserved, then we can use the memory arbitrarily. Adding
> non-reserved regions is jsut defeating mem=, no?
>
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index d45f862..2a20d02 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -46,6 +46,7 @@
> > #include <asm/sizes.h>
> > #include <asm/tlb.h>
> > #include <asm/alternative.h>
> > +#include <asm/memblock.h>
>
> While this is already unordered, only the asm/alternative.h include is
> out of place. Please try to put the include earlier to as to keep this
> ordered.
>
> > @@ -210,6 +216,19 @@ static __init void reserve_regions(void)
> > if (resv)
> > memblock_mark_nomap(paddr, size);
> >
> > +#ifdef CONFIG_ACPI
> > + if (md->type == EFI_ACPI_RECLAIM_MEMORY ||
> > + md->type == EFI_ACPI_MEMORY_NVS) {
> > + if (nr_acpi_regs >= MAX_ACPI_REGS) {
> > + WARN_ONCE(1, "Too many ACPI mem regions: %d\n", nr_acpi_regs);
> > + continue;
> > + }
> > + acpi_regs[nr_acpi_regs].base = paddr;
> > + acpi_regs[nr_acpi_regs].size = size;
> > + acpi_regs[nr_acpi_regs].resv = resv;
> > + nr_acpi_regs++;
> > + }
> > +#endif
>
> It it's not reserved, I don't see the point in adding it. Surely all of
> these should be reserved?
>
> Thanks,
> Mark.
>
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