Re: [PATCH v9 13/13] cxl: Disable HPA/SPA translation handlers for Normalized Addressing

[Dave Jiang <dave.jiang@intel.com>]

On 1/10/26 4:46 AM, Robert Richter wrote:
> The root decoder provides the callbacks hpa_to_spa and spa_to_hpa to
> perform Host Physical Address (HPA) and System Physical Address
> translations, respectively. The callbacks are required to convert
> addresses when HPA != SPA. XOR interleaving depends on this mechanism,
> and the necessary handlers are implemented.
> 
> The translation handlers are used for poison injection
> (trace_cxl_poison, cxl_poison_inject_fops) and error handling
> (cxl_event_trace_record).
> 
> In AMD Zen5 systems with Normalized Addressing, endpoint addresses are
> not SPAs, and translation handlers are required for these features to
> function correctly.
> 
> Now, as ACPI PRM translation could be expensive in tracing or error
> handling code paths, do not yet enable translations to avoid its
> intensive use. Instead, disable those features which are used only for
> debugging and enhanced logging.
> 
> Introduce the flag CXL_REGION_F_NORM_ADDR that indicates Normalized
> Addressing for a region and use it to disable poison injection and DPA
> to HPA conversion.
> 
> Note: Dropped unused CXL_DECODER_F_MASK macro.
> 
> Signed-off-by: Robert Richter <rrichter@amd.com>
> ---
>  drivers/cxl/core/atl.c    |  3 +++
>  drivers/cxl/core/region.c | 33 +++++++++++++++++++++++++--------
>  drivers/cxl/cxl.h         |  9 ++++++++-
>  3 files changed, 36 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/cxl/core/atl.c b/drivers/cxl/core/atl.c
> index 09d0ea1792d9..13f1118dc026 100644
> --- a/drivers/cxl/core/atl.c
> +++ b/drivers/cxl/core/atl.c
> @@ -169,8 +169,11 @@ static int cxl_prm_setup_root(struct cxl_root *cxl_root, void *data)
>  	 * decoders in the BIOS would prevent a capable kernel (or
>  	 * other operating systems) from shutting down auto-generated
>  	 * regions and managing resources dynamically.
> +	 *
> +	 * Indicate that Normalized Addressing is enabled.
>  	 */
>  	cxld->flags |= CXL_DECODER_F_LOCK;
> +	cxld->flags |= CXL_DECODER_F_NORM_ADDR;

IMO,
Spelling out NORMALIZED probably make the flag clearer the address is normalized vs a normal address.

DJ
>  
>  	ctx->hpa_range = hpa_range;
>  	ctx->interleave_ways = ways;
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 80cd77f0842e..8b68ccce1554 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1097,14 +1097,16 @@ static int cxl_rr_assign_decoder(struct cxl_port *port, struct cxl_region *cxlr,
>  	return 0;
>  }
>  
> -static void cxl_region_set_lock(struct cxl_region *cxlr,
> -				struct cxl_decoder *cxld)
> +static void cxl_region_setup_flags(struct cxl_region *cxlr,
> +				   struct cxl_decoder *cxld)
>  {
> -	if (!test_bit(CXL_DECODER_F_LOCK, &cxld->flags))
> -		return;
> +	if (test_bit(CXL_DECODER_F_LOCK, &cxld->flags)) {
> +		set_bit(CXL_REGION_F_LOCK, &cxlr->flags);
> +		clear_bit(CXL_REGION_F_NEEDS_RESET, &cxlr->flags);
> +	}
>  
> -	set_bit(CXL_REGION_F_LOCK, &cxlr->flags);
> -	clear_bit(CXL_REGION_F_NEEDS_RESET, &cxlr->flags);
> +	if (test_bit(CXL_DECODER_F_NORM_ADDR, &cxld->flags))
> +		set_bit(CXL_REGION_F_NORM_ADDR, &cxlr->flags);
>  }
>  
>  /**
> @@ -1218,7 +1220,7 @@ static int cxl_port_attach_region(struct cxl_port *port,
>  		}
>  	}
>  
> -	cxl_region_set_lock(cxlr, cxld);
> +	cxl_region_setup_flags(cxlr, cxld);
>  
>  	rc = cxl_rr_ep_add(cxl_rr, cxled);
>  	if (rc) {
> @@ -2493,7 +2495,7 @@ static struct cxl_region *cxl_region_alloc(struct cxl_root_decoder *cxlrd, int i
>  	device_set_pm_not_required(dev);
>  	dev->bus = &cxl_bus_type;
>  	dev->type = &cxl_region_type;
> -	cxl_region_set_lock(cxlr, &cxlrd->cxlsd.cxld);
> +	cxl_region_setup_flags(cxlr, &cxlrd->cxlsd.cxld);
>  
>  	return cxlr;
>  }
> @@ -3132,6 +3134,13 @@ u64 cxl_dpa_to_hpa(struct cxl_region *cxlr, const struct cxl_memdev *cxlmd,
>  	u8 eiw = 0;
>  	int pos;
>  
> +	/*
> +	 * Conversion between SPA and DPA is not supported in
> +	 * Normalized Address mode.
> +	 */
> +	if (test_bit(CXL_REGION_F_NORM_ADDR, &cxlr->flags))
> +		return ULLONG_MAX;
> +
>  	for (int i = 0; i < p->nr_targets; i++) {
>  		if (cxlmd == cxled_to_memdev(p->targets[i])) {
>  			cxled = p->targets[i];
> @@ -3922,6 +3931,14 @@ static int cxl_region_setup_poison(struct cxl_region *cxlr)
>  	struct cxl_region_params *p = &cxlr->params;
>  	struct dentry *dentry;
>  
> +	/*
> +	 * Do not enable poison injection in Normalized Address mode.
> +	 * Conversion between SPA and DPA is required for this, but it is
> +	 * not supported in this mode.
> +	 */
> +	if (test_bit(CXL_REGION_F_NORM_ADDR, &cxlr->flags))
> +		return 0;
> +
>  	/* Create poison attributes if all memdevs support the capabilities */
>  	for (int i = 0; i < p->nr_targets; i++) {
>  		struct cxl_endpoint_decoder *cxled = p->targets[i];
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 20b0fd43fa7b..0ab0a86e1d4f 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -332,7 +332,7 @@ int cxl_dport_map_rcd_linkcap(struct pci_dev *pdev, struct cxl_dport *dport);
>  #define CXL_DECODER_F_TYPE3 BIT(3)
>  #define CXL_DECODER_F_LOCK  BIT(4)
>  #define CXL_DECODER_F_ENABLE    BIT(5)
> -#define CXL_DECODER_F_MASK  GENMASK(5, 0)
> +#define CXL_DECODER_F_NORM_ADDR BIT(6)
>  
>  enum cxl_decoder_type {
>  	CXL_DECODER_DEVMEM = 2,
> @@ -525,6 +525,13 @@ enum cxl_partition_mode {
>   */
>  #define CXL_REGION_F_LOCK 2
>  
> +/*
> + * Indicate Normalized Addressing. Use it to disable SPA conversion if
> + * HPA != SPA and an address translation callback handler does not
> + * exist. Flag is needed by AMD Zen5 platforms.
> + */
> +#define CXL_REGION_F_NORM_ADDR 3
> +
>  /**
>   * struct cxl_region - CXL region
>   * @dev: This region's device