Subject: [PATCH 2/3] hotplug-memory.c: enhance dlpar_memory_remove* LMB checks

From: Daniel Henrique Barboza <[email-masked]>
Date: Fri, 30 Apr 2021 09:09:16 -0300

dlpar_memory_remove_by_ic() validates the amount of LMBs to be removed
by checking !DRCONF_MEM_RESERVED, and in the following loop before
dlpar_remove_lmb() a check for DRCONF_MEM_ASSIGNED is made before
removing it. This means that a LMB that is both !DRCONF_MEM_RESERVED and
!DRCONF_MEM_ASSIGNED will be counted as valid, but then not being
removed.  The function will end up not removing all 'lmbs_to_remove'
LMBs while also not reporting any errors.

Comparing it to dlpar_memory_remove_by_count(), the validation is done
via lmb_is_removable(), which checks for DRCONF_MEM_ASSIGNED and fadump
constraints. No additional check is made afterwards, and
DRCONF_MEM_RESERVED is never checked before dlpar_remove_lmb(). The
function doesn't have the same 'check A for validation, then B for
removal' issue as remove_by_ic(), but it's not checking if the LMB is
reserved.

There is no reason for these functions to validate the same operation in
two different manners. This patch addresses that by changing
lmb_is_removable() to also check for DRCONF_MEM_RESERVED to tell if a
lmb is removable, making dlpar_memory_remove_by_count() take the
reservation state into account when counting the LMBs.
lmb_is_removable() is then used in the validation step of
dlpar_memory_remove_by_ic(), which is already checking for both states
but in different stages, to avoid counting a LMB that is not assigned as
eligible for removal. We can then skip the check before
dlpar_remove_lmb() since we're validating all LMBs beforehand.

Signed-off-by: Daniel Henrique Barboza <[email-masked]>
---
 arch/powerpc/platforms/pseries/hotplug-memory.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index bb98574a84a2..4e6d162c3f1a 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -348,7 +348,8 @@ static int pseries_remove_mem_node(struct device_node *np)
 
 static bool lmb_is_removable(struct drmem_lmb *lmb)
 {
-	if (!(lmb->flags & DRCONF_MEM_ASSIGNED))
+	if ((lmb->flags & DRCONF_MEM_RESERVED) ||
+		!(lmb->flags & DRCONF_MEM_ASSIGNED))
 		return false;
 
 #ifdef CONFIG_FA_DUMP
@@ -523,7 +524,7 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
 
 	/* Validate that there are enough LMBs to satisfy the request */
 	for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
-		if (lmb->flags & DRCONF_MEM_RESERVED)
+		if (!lmb_is_removable(lmb))
 			break;
 
 		lmbs_available++;
@@ -533,9 +534,6 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
 		return -EINVAL;
 
 	for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
-		if (!(lmb->flags & DRCONF_MEM_ASSIGNED))
-			continue;
-
 		rc = dlpar_remove_lmb(lmb);
 		if (rc)
 			break;
-- 
2.30.2