linux-kernel - [PATCH] powerpc/hotplug: assign hot added LMB to the right node

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Date:   Thu,  3 Dec 2020 11:15:14 +0100
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        Scott Cheloha <cheloha@...ux.ibm.com>, stable@...r.kernel.org
Subject: [PATCH] powerpc/hotplug: assign hot added LMB to the right node

This patch applies to 5.9 and earlier kernels only.

Since 5.10, this has been fortunately fixed by the commit
e5e179aa3a39 ("pseries/drmem: don't cache node id in drmem_lmb struct").

When LMBs are added to a running system, the node id assigned to the LMB is
fetched from the temporary DT node provided by the hypervisor.

However, LMBs added are always assigned to the first online node. This is a
mistake and this is because hot_add_drconf_scn_to_nid() called by
lmb_set_nid() is checking for the LMB flags DRCONF_MEM_ASSIGNED which is
set later in dlpar_add_lmb().

To fix this issue, simply set that flag earlier in dlpar_add_lmb().

Note, this code has been rewrote in 5.10 and thus this fix has no meaning
since this version.

Signed-off-by: Laurent Dufour <ldufour@...ux.ibm.com>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Nathan Lynch <nathanl@...ux.ibm.com>
Cc: Scott Cheloha <cheloha@...ux.ibm.com>
Cc: linuxppc-dev@...ts.ozlabs.org
Cc: stable@...r.kernel.org
---
 arch/powerpc/platforms/pseries/hotplug-memory.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index e54dcbd04b2f..92d83915c629 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -663,12 +663,14 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
 		return rc;
 	}
 
+	lmb->flags |= DRCONF_MEM_ASSIGNED;
 	lmb_set_nid(lmb);
 	block_sz = memory_block_size_bytes();
 
 	/* Add the memory */
 	rc = __add_memory(lmb->nid, lmb->base_addr, block_sz);
 	if (rc) {
+		lmb->flags &= ~DRCONF_MEM_ASSIGNED;
 		invalidate_lmb_associativity_index(lmb);
 		return rc;
 	}
@@ -676,10 +678,9 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
 	rc = dlpar_online_lmb(lmb);
 	if (rc) {
 		__remove_memory(lmb->nid, lmb->base_addr, block_sz);
+		lmb->flags &= ~DRCONF_MEM_ASSIGNED;
 		invalidate_lmb_associativity_index(lmb);
 		lmb_clear_nid(lmb);
-	} else {
-		lmb->flags |= DRCONF_MEM_ASSIGNED;
 	}
 
 	return rc;
-- 
2.29.2