Re: [PATCH] cxl/region: Move coherence tracking into cxl_region_attach()

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

On 3/28/23 11:36 AM, Dan Williams wrote:
> Each time the contents of a given HPA are potentially changed in a cache
> incoherent manner the CXL core sets CXL_REGION_F_INCOHERENT to
> invalidate CPU caches before the region is used.
> 
> Successful invocation of attach_target() indicates that DPA has been
> newly assigned to a given HPA in the dynamic region creation flow.
> However, attach_target() is also reused in the autodiscovery flow where
> the region was activated by platform firmware. In that case there is no
> need to invalidate caches because that region is already in active use
> and nothing about the autodiscovery flow modifies the HPA-to-DPA
> relationship.
> 
> Fixes: a32320b71f08 ("cxl/region: Add region autodiscovery")
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>   drivers/cxl/core/region.c |    3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 52bbf6268d5f..b2fd67fcebfb 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1674,6 +1674,7 @@ static int cxl_region_attach(struct cxl_region *cxlr,
>   		if (rc)
>   			goto err_decrement;
>   		p->state = CXL_CONFIG_ACTIVE;
> +		set_bit(CXL_REGION_F_INCOHERENT, &cxlr->flags);
>   	}
>   
>   	cxled->cxld.interleave_ways = p->interleave_ways;
> @@ -1775,8 +1776,6 @@ static int attach_target(struct cxl_region *cxlr,
>   
>   	down_read(&cxl_dpa_rwsem);
>   	rc = cxl_region_attach(cxlr, cxled, pos);
> -	if (rc == 0)
> -		set_bit(CXL_REGION_F_INCOHERENT, &cxlr->flags);
>   	up_read(&cxl_dpa_rwsem);
>   	up_write(&cxl_region_rwsem);
>   	return rc;
>