Re: [PATCH v3 2/4] cxl: Update Soft Reserved resources upon region creation

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Thu, 3 Apr 2025 13:33:13 -0500
Terry Bowman <terry.bowman@amd.com> wrote:

> From: Nathan Fontenot <nathan.fontenot@amd.com>
> 
> Update handling of SOFT RESERVE iomem resources that intersect with
> CXL region resources to remove intersections from the SOFT RESERVE
> resources. The current approach of leaving SOFT RESERVE resources as
> is can cause failures during hotplug replace of CXL devices because
> the resource is not available for reuse after teardown of the CXL device.
> 
> To accomplish this the cxl acpi driver creates a worker thread at the

Inconsistent in capitalization. I'd just use CXL ACPI here given you used CXL PCI
below.

> end of cxl_acpi_probe(). This worker thread first waits for the CXL PCI
> CXL mem drivers have loaded. The cxl core/suspend.c code is updated to
> add a pci_loaded variable, in addition to the mem_active variable, that
> is updated when the pci driver loads. Remove CONFIG_CXL_SUSPEND Kconfig as
> it is no longer needed. A new cxl_wait_for_pci_mem() routine uses a
> waitqueue for both these driver to be loaded. The need to add this
> additional waitqueue is ensure the CXL PCI and CXL mem drivers have loaded
> before we wait for their probe, without it the cxl acpi probe worker thread
> calls wait_for_device_probe() before these drivers are loaded.
> 
> After the CXL PCI and CXL mem drivers load the cxl acpi worker thread
CXL ACPI

> uses wait_for_device_probe() to ensure device probe routines have
> completed.

Does it matter if these drivers go away again?  Everything seems
to be one way at the moment.

> 
> Once probe completes and regions have been created, find all cxl

CXL

> regions that have been created and trim any SOFT RESERVE resources
> that intersect with the region.
> 
> Update cxl_acpi_exit() to cancel pending waitqueue work.
> 
> Signed-off-by: Nathan Fontenot <nathan.fontenot@amd.com>
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>


> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index be8a7dc77719..40835ec692c8 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -858,6 +858,7 @@ bool is_cxl_pmem_region(struct device *dev);
>  struct cxl_pmem_region *to_cxl_pmem_region(struct device *dev);
>  int cxl_add_to_region(struct cxl_port *root,
>  		      struct cxl_endpoint_decoder *cxled);
> +int cxl_region_srmem_update(void);

As before: srmem is a bit obscure. Maybe spell it out more.

>  struct cxl_dax_region *to_cxl_dax_region(struct device *dev);
>  u64 cxl_port_get_spa_cache_alias(struct cxl_port *endpoint, u64 spa);
>  #else
> @@ -902,6 +903,8 @@ void cxl_coordinates_combine(struct access_coordinate *out,
>  
>  bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
>  
> +void cxl_wait_for_pci_mem(void);