On Fri, 16 Aug 2024 10:07:23 +0800 Huang Ying <ying.huang@xxxxxxxxx> wrote:
> On a system with CXL memory installed, the resource tree (/proc/iomem)
> related to CXL memory looks like something as follows.
>
> 490000000-50fffffff : CXL Window 0
> 490000000-50fffffff : region0
> 490000000-50fffffff : dax0.0
> 490000000-50fffffff : System RAM (kmem)
>
> When the following command line is run to try writing some memory in
> CXL memory range,
>
> $ dd if=data of=/dev/mem bs=1k seek=19136512 count=1
> dd: error writing '/dev/mem': Bad address
> 1+0 records in
> 0+0 records out
> 0 bytes copied, 0.0283507 s, 0.0 kB/s
>
> the command fails as expected. However, the error code is wrong. It
> should be "Operation not permitted" instead of "Bad address". And,
> the following warning is reported in kernel log.
>
> ioremap on RAM at 0x0000000490000000 - 0x0000000490000fff
> WARNING: CPU: 2 PID: 416 at arch/x86/mm/ioremap.c:216 __ioremap_caller.constprop.0+0x131/0x35d
> ...
>
Presumably we want to fix earlier kernels? If so, are you able to
identify a suitable Fixes: target? Possibly 974854ab0728 ("cxl/acpi:
Track CXL resources in iomem_resource")?
