RE: [PATCH] cxl/port: Disable decoder setup for endpoints in RCD mode

[Dan Williams]

Robert Richter wrote:
> In RCD mode the HDM decoder capability is optional for endpoints and
> may not exist. The HDM range registers are used instead. Since the
> driver relies on the existence of an HDM decoder capability, its
> absence will cause the initialization of a memory card to fail.
> 
> Moreover, the driver also tries to enable or reuse enabled memory
> ranges. In the worst case this may lead to a system hang due to
> disabling system memory that was previously provided and setup by
> system firmware.
> 
> To solve the issues described, disable decoder setup for RCD endpoints
> and instead rely exclusively on system firmware to enable those memory
> ranges. Decoders are used by the kernel to setup and configure CXL
> memory regions, esp. to enable and disable them. Since Hot-plug is not
> supported for devices in RCD mode, the ability to disable that memory
> by the kernel using a decoder is not a necessarily requirement,
> decoders are not needed then.
> 
> Fixes: 34e37b4c432c ("cxl/port: Enable HDM Capability after validating DVSEC Ranges")
> Signed-off-by: Robert Richter <rrichter@xxxxxxx>

Does Dave's series address this problem?

https://lore.kernel.org/linux-cxl/167588394236.1155956.8466475582138210344.stgit@djiang5-mobl3.local/

...that is arranging for the driver to carry-on in the absence of the
HDM Decoder Capability.