Hi,
On 9/22/21 6:11 AM, Ard Biesheuvel wrote:
On Tue, 21 Sept 2021 at 12:05, Lorenzo Pieralisi
<lorenzo.pieralisi@xxxxxxx> wrote:
On Mon, Sep 20, 2021 at 07:32:56PM +0200, Rafael J. Wysocki wrote:
On Mon, Sep 20, 2021 at 7:03 PM Lorenzo Pieralisi
<lorenzo.pieralisi@xxxxxxx> wrote:
On Thu, Sep 16, 2021 at 05:08:27PM +0100, Lorenzo Pieralisi wrote:
On Fri, Sep 10, 2021 at 07:28:49PM +0200, Ard Biesheuvel wrote:
On Fri, 10 Sept 2021 at 16:32, Jia He <justin.he@xxxxxxx> wrote:
This reverts commit 437b38c51162f8b87beb28a833c4d5dc85fa864e.
After this commit, a boot panic is alway hit on an Ampere EMAG server
with call trace as follows:
Internal error: synchronous external abort: 96000410 [#1] SMP
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0+ #462
Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 0.14 02/22/2019
pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[...snip...]
Call trace:
acpi_ex_system_memory_space_handler+0x26c/0x2c8
acpi_ev_address_space_dispatch+0x228/0x2c4
acpi_ex_access_region+0x114/0x268
acpi_ex_field_datum_io+0x128/0x1b8
acpi_ex_extract_from_field+0x14c/0x2ac
acpi_ex_read_data_from_field+0x190/0x1b8
acpi_ex_resolve_node_to_value+0x1ec/0x288
acpi_ex_resolve_to_value+0x250/0x274
acpi_ds_evaluate_name_path+0xac/0x124
acpi_ds_exec_end_op+0x90/0x410
acpi_ps_parse_loop+0x4ac/0x5d8
acpi_ps_parse_aml+0xe0/0x2c8
acpi_ps_execute_method+0x19c/0x1ac
acpi_ns_evaluate+0x1f8/0x26c
acpi_ns_init_one_device+0x104/0x140
acpi_ns_walk_namespace+0x158/0x1d0
acpi_ns_initialize_devices+0x194/0x218
acpi_initialize_objects+0x48/0x50
acpi_init+0xe0/0x498
As mentioned by Lorenzo:
"We are forcing memory semantics mappings to PROT_NORMAL_NC, which
eMAG does not like at all and I'd need to understand why. It looks
like the issue happen in SystemMemory Opregion handler."
Hence just revert it before everything is clear.
Can we try to find the root cause first? -rc1 is not even out yet, and
reverting it now means we can not resubmit it until the next merge
window.
I am waiting to debug this on an eMAG but I noticed something that
I wanted to bring up.
SystemMemory Operation region handler - ie
acpi_ex_system_memory_space_handler()
maps the Operation Region (that AFAICS is MMIO, it is _not_ memory)
with acpi_os_map_memory() and I believe that's what is causing this
bug.
On the other hand, acpi_os_map_generic_address(), to handle spaceid
ACPI_ADR_SPACE_SYSTEM_MEMORY, uses acpi_os_map_iomem() that is more
in line with my expectations.
Hi Rafael,
I wanted to ask please if you have any insights on why
(1) acpi_ex_system_memory_space_handler()
(2) acpi_os_map_generic_address()
Use two different calls to map memory for the _same_ address space ID
(SystemMemory).
(3) acpi_os_map_memory()
vs
(4) acpi_os_map_iomem()
I don't really have a good answer here.
On x86 this doesn't really matter and that's where
acpi_ex_system_memory_space_handler() was first introduced. It is not
only used for IOMEM (there are SystemMemory operation regions in RAM),
but since it may be in IOMEM, it should assume so.
I am struggling to understand why (1) uses (3) ("memory semantics") when
(2) uses (4) - it is actually unclear how the distinction between
the two mapping APIs is to be drawn and on what basis one should
choose which one to use.
I am still waiting to grab some HW to debug this report but the issue
here is that we are mapping an OpRegion SystemMemory with (3) in the
memory space handler and given the patch we are reverting we end up
mapping the operation region with normal non-cacheable memory attributes
that probably the physical address range behind the OpRegion does not
support.
If that is the case, there needs to be a mechanism to decide what kind
of mapping to use for SystemMemory operation regions based on the type
of physical memory the address range in question is located in.
Thank you Rafael. The mechanism we are currently relying on is the EFI
memory map but if the Opregion address is not described there then we
are left with a default choice to make (theoretically I may also parse
all _CRS in the namespace to find whether a resource include the
Opregion and I may infer attributes from the _CRS resource entry).
I'm not sure that would help, as I would expected the memory described
by _CRS to be mostly mutually exclusive from memory used by OpRegions.
Maybe we should update the ACPI specs to enforce it; with current
firmware the idea of using the OS expected *usage* of memory (ie
memory vs IO) described by the mapping function prototype can't work
as this revert shows (even though it would be better if I manage
to find what the precise issue is).
We can't map something with specific attributes if we don't know
whether the physical address space backing the region supports it.
We don't have a a safe default in either direction, so I agree this is
a hole in the specs.
I just debugged down to this patch because of boot failures with the
rpi4. Then I found this thread.
I had always assumed that SystemIO was x86/PIO, and SystemMemory was
defined as MMIO but on arm we would have to determine if the memory
region was described in the uefi memory map as actual system ram, and if
not assume device memory. I was looking at tweaking acpi_map() to check
that similar to what is happening on !arm64.
Gotta run, but throwing that out there since it seems a possible fix
without creating a new OpregionType to differentiate actual memory vs MMIO.
I am left with little choice: I assume the best thing I could do
to fix the original bug is to use ioremap_* in acpi_data_show()
instead of acpi_os_map/unmap_memory() to map that memory with
specific attributes (for BERT error regions, they must be RAM
so, _hopefully_, we know it can be mapped with eg normal memory
mappings).
Thoughts ?
One thing I just realized is that the EFI memory map is not a complete
solution to begin with, as it may not cover hot/coldplugged memory
regions that are only described via ACPI.
Did you make any progress with the eMAG?
