Re: [PATCH v5 2/3] ACPI, APEI, EINJ: Add CXL 1.1 EINJ error type support

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Sep 25, 2023 at 03:01:26PM -0500, Ben Cheatham wrote:
> Add support for CXL EINJ error types for CXL 1.1 hosts added in ACPI
> v6.5. Because these error types target memory-mapped CXL 1.1 compliant
> downstream ports and not physical (normal/persistent) memory, these
> error types are not currently  allowed through the memory range
> validation done by the EINJ driver.
> 
> The MMIO address of a CXL 1.1 downstream port can be found in the
> cxl_rcrb_addr file in the corresponding dport directory under
> /sys/bus/cxl/devices/portX. CXL 1.1 error types follow the same
> procedure as a memory error type, but with param1 set to the
> downstream port MMIO address.
> 
> Example usage:
> $ cd /sys/kernel/debug/apei/einj
> $ cat available_error_type
>     0x00000008      Memory Correctable
>     0x00000010      Memory Uncorrectable non-fatal
>     0x00000020      Memory Uncorrectable fatal
>     0x00000040      PCI Express Correctable
>     0x00000080      PCI Express Uncorrectable non-fatal
>     0x00000100      PCI Express Uncorrectable fatal
>     0x00008000      CXL.mem Protocol Correctable
>     0x00020000      CXL.mem Protocol Uncorrectable fatal
> $ echo 0x8000 > error_type
> $ echo 0xfffffffffffff000 > param2
> $ echo 0x2 > flags
> $ cat /sys/bus/cxl/devices/portX/dportY/cxl_rcrb_addr
> 0xb2f00000
> $ echo 0xb2f00000 > param1

It seems sort of unpleasant to expose the physical base address of the
RCRB.  Is there any way to use a device address or other logical
identifier instead and keep the actual MMIO address internal?  E.g., a
PCI device has a <domain>:<bus>:<device>.<function> address.  I assume
CXL addresses would look similar?

> $ echo 1 > error_inject
> ...

> +static int is_valid_cxl_addr(u64 addr)

Maybe the function name should include a hint that this should be an
RCRB address?  But I don't claim to know the CXL architecture or
nomenclature.

Bjorn