[PATCH v2 4/4] powerpc/pseries: minor enhancements in dlpar_memory_remove_by_ic()

[David Gibson]

On Wed, May 12, 2021 at 05:28:09PM -0300, Daniel Henrique Barboza wrote:
> We don't need the 'lmbs_available' variable to count the valid LMBs and
> to check if we have less than 'lmbs_to_remove'. We must ensure that the
> entire LMB range must be removed, so we can error out immediately if any
> LMB in the range is marked as reserved.
> 
> Add a couple of comments explaining the reasoning behind the differences
> we have in this function in contrast to what it is done in its sister
> function, dlpar_memory_remove_by_count().
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>

Reviewed-by: David Gibson <david at gibson.dropbear.id.au>

> ---
>  .../platforms/pseries/hotplug-memory.c        | 28 +++++++++++++------
>  1 file changed, 19 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 3c7ce5361ce3..ee88c1540fba 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -517,7 +517,6 @@ static int dlpar_memory_remove_by_index(u32 drc_index)
>  static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
>  {
>  	struct drmem_lmb *lmb, *start_lmb, *end_lmb;
> -	int lmbs_available = 0;
>  	int rc;
>  
>  	pr_info("Attempting to hot-remove %u LMB(s) at %x\n",
> @@ -530,18 +529,29 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
>  	if (rc)
>  		return -EINVAL;
>  
> -	/* Validate that there are enough LMBs to satisfy the request */
> +	/*
> +	 * Validate that all LMBs in range are not reserved. Note that it
> +	 * is ok if they are !ASSIGNED since our goal here is to remove the
> +	 * LMB range, regardless of whether some LMBs were already removed
> +	 * by any other reason.
> +	 *
> +	 * This is a contrast to what is done in remove_by_count() where we
> +	 * check for both RESERVED and !ASSIGNED (via lmb_is_removable()),
> +	 * because we want to remove a fixed amount of LMBs in that function.
> +	 */
>  	for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
> -		if (lmb->flags & DRCONF_MEM_RESERVED)
> -			break;
> -
> -		lmbs_available++;
> +		if (lmb->flags & DRCONF_MEM_RESERVED) {
> +			pr_err("Memory at %llx (drc index %x) is reserved\n",
> +				lmb->base_addr, lmb->drc_index);
> +			return -EINVAL;
> +		}
>  	}
>  
> -	if (lmbs_available < lmbs_to_remove)
> -		return -EINVAL;
> -
>  	for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
> +		/*
> +		 * dlpar_remove_lmb() will error out if the LMB is already
> +		 * !ASSIGNED, but this case is a no-op for us.
> +		 */
>  		if (!(lmb->flags & DRCONF_MEM_ASSIGNED))
>  			continue;
>  

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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