Re: [PATCH v1 1/2] cxl/edac: Fix the min_scrub_cycle of a region miscalculation

[Davidlohr Bueso]

On Tue, 03 Jun 2025, Li Ming wrote:

> When trying to update the scrub_cycle value of a cxl region, which means
> updating the scrub_cycle value of each memdev under a cxl region. cxl
> driver needs to guarantee the new scrub_cycle value is greater than the
> min_scrub_cycle value of a memdev, otherwise the updating operation will
> fail(Per Table 8-223 in CXL r3.2 section 8.2.10.9.11.1).
>
> Current implementation logic of getting the min_scrub_cycle value of a
> cxl region is that getting the min_scrub_cycle value of each memdevs
> under the cxl region, then using the minimum min_scrub_cycle value as
> the region's min_scrub_cycle. Checking if the new scrub_cycle value is
> greater than this value. If yes, updating the new scrub_cycle value to
> each memdevs. The issue is that the new scrub_cycle value is possibly
> greater than the minimum min_scrub_cycle value of all memdevs but less
> than the maximum min_scrub_cycle value of all memdevs if memdevs have
> a different min_scrub_cycle value. The updating operation will always
> fail on these memdevs which have a greater min_scrub_cycle than the new
> scrub_cycle.
>
> The correct implementation logic is to get the maximum value of these
> memdevs' min_scrub_cycle, check if the new scrub_cycle value is greater
> than the value. If yes, the new scrub_cycle value is fit for the region.
>
> The change also impacts the result of
> cxl_patrol_scrub_get_min_scrub_cycle(), the interface returned the
> minimum min_scrub_cycle value among all memdevs under the region before
> the change. The interface will return the maximum min_scrub_cycle value
> among all memdevs under the region with the change.
>
> Signed-off-by: Li Ming <ming.li@xxxxxxxxxxxx>

Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>