Le 30/07/2020 à 15:33, Pingfan Liu a écrit :
A bug is observed on pseries by taking the following steps on rhel:
-1. drmgr -c mem -r -q 5
-2. echo c > /proc/sysrq-trigger
And then, the failure looks like:
kdump: saving to /sysroot//var/crash/127.0.0.1-2020-01-16-02:06:14/
kdump: saving vmcore-dmesg.txt
kdump: saving vmcore-dmesg.txt complete
kdump: saving vmcore
Checking for memory holes : [ 0.0 %] / Checking for memory holes : [100.0 %] | Excluding unnecessary pages : [100.0 %] \ Copying data : [ 0.3 %] - eta: 38s[ 44.337636] hash-mmu: mm: Hashing failure ! EA=0x7fffba400000 access=0x8000000000000004 current=makedumpfile
[ 44.337663] hash-mmu: trap=0x300 vsid=0x13a109c ssize=1 base psize=2 psize 2 pte=0xc000000050000504
[ 44.337677] hash-mmu: mm: Hashing failure ! EA=0x7fffba400000 access=0x8000000000000004 current=makedumpfile
[ 44.337692] hash-mmu: trap=0x300 vsid=0x13a109c ssize=1 base psize=2 psize 2 pte=0xc000000050000504
[ 44.337708] makedumpfile[469]: unhandled signal 7 at 00007fffba400000 nip 00007fffbbc4d7fc lr 000000011356ca3c code 2
[ 44.338548] Core dump to |/bin/false pipe failed
/lib/kdump-lib-initramfs.sh: line 98: 469 Bus error $CORE_COLLECTOR /proc/vmcore $_mp/$KDUMP_PATH/$HOST_IP-$DATEDIR/vmcore-incomplete
kdump: saving vmcore failed
* Root cause *
After analyzing, it turns out that in the current implementation,
when hot-removing lmb, the KOBJ_REMOVE event ejects before the dt updating as
the code __remove_memory() comes before drmem_update_dt().
So in kdump kernel, when read_from_oldmem() resorts to
pSeries_lpar_hpte_insert() to install hpte, but fails with -2 due to
non-exist pfn. And finally, low_hash_fault() raise SIGBUS to process, as it
can be observed "Bus error"
From a viewpoint of listener and publisher, the publisher notifies the
listener before data is ready. This introduces a problem where udev
launches kexec-tools (due to KOBJ_REMOVE) and loads a stale dt before
updating. And in capture kernel, makedumpfile will access the memory based
on the stale dt info, and hit a SIGBUS error due to an un-existed lmb.
* Fix *
This bug is introduced by commit 063b8b1251fd
("powerpc/pseries/memory-hotplug: Only update DT once per memory DLPAR
request"), which tried to combine all the dt updating into one.
To fix this issue, meanwhile not to introduce a quadratic runtime
complexity by the model:
dlpar_memory_add_by_count
for_each_drmem_lmb <--
dlpar_add_lmb
drmem_update_dt(_v1|_v2)
for_each_drmem_lmb <--
The dt should still be only updated once, and just before the last memory
online/offline event is ejected to user space. Achieve this by tracing the
num of lmb added or removed.
Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx>
Cc: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
Cc: Nathan Fontenot <nfont@xxxxxxxxxxxxxxxxxx>
Cc: kexec@xxxxxxxxxxxxxxxxxxx
To: linuxppc-dev@xxxxxxxxxxxxxxxx
---
v3 -> v4: resolve a quadratic runtime complexity issue.
This series is applied on next-test branch
arch/powerpc/platforms/pseries/hotplug-memory.c | 88 ++++++++++++++++++-------
1 file changed, 66 insertions(+), 22 deletions(-)
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 1a3ac3b..e07d5b1 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -350,13 +350,13 @@ static bool lmb_is_removable(struct drmem_lmb *lmb)
return true;
}
-static int dlpar_add_lmb(struct drmem_lmb *);
+static int dlpar_add_lmb(struct drmem_lmb *lmb, bool dt_update);
-static int dlpar_remove_lmb(struct drmem_lmb *lmb)
+static int dlpar_remove_lmb(struct drmem_lmb *lmb, bool dt_update)
{
unsigned long block_sz;
phys_addr_t base_addr;
- int rc, nid;
+ int rc, ret, nid;
if (!lmb_is_removable(lmb))
return -EINVAL;
@@ -372,6 +372,11 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
invalidate_lmb_associativity_index(lmb);
lmb_clear_nid(lmb);
lmb->flags &= ~DRCONF_MEM_ASSIGNED;
+ if (dt_update) {
+ ret = drmem_update_dt();
+ if (ret)
+ pr_warn("%s fail to update dt, but continue\n", __func__);
+ }
__remove_memory(nid, base_addr, block_sz);
@@ -387,6 +392,7 @@ static int dlpar_memory_remove_by_count(u32 lmbs_to_remove)
int lmbs_removed = 0;
int lmbs_available = 0;
int rc;
+ bool dt_update = false;
pr_info("Attempting to hot-remove %d LMB(s)\n", lmbs_to_remove);
@@ -409,7 +415,7 @@ static int dlpar_memory_remove_by_count(u32 lmbs_to_remove)
}
for_each_drmem_lmb(lmb) {
- rc = dlpar_remove_lmb(lmb);
+ rc = dlpar_remove_lmb(lmb, dt_update);
if (rc)
continue;
@@ -421,16 +427,27 @@ static int dlpar_memory_remove_by_count(u32 lmbs_to_remove)
lmbs_removed++;
if (lmbs_removed == lmbs_to_remove)
break;
+ /* combine dt updating */
+ else if (lmbs_removed == lmbs_to_remove - 1)
+ dt_update = true;
}
if (lmbs_removed != lmbs_to_remove) {
+ bool rollback_dt_update = false;
+
pr_err("Memory hot-remove failed, adding LMB's back\n");
for_each_drmem_lmb(lmb) {
if (!drmem_lmb_reserved(lmb))
continue;
- rc = dlpar_add_lmb(lmb);
+ /*
+ * Even if dlpar_remove_lmb() fails to update dt, it is
+ * harmless to update dt here.
+ */
+ if (--lmbs_removed == 0 && dt_update)
+ rollback_dt_update = true;
+ rc = dlpar_add_lmb(lmb, rollback_dt_update);
if (rc)
pr_err("Failed to add LMB back, drc index %x\n",
lmb->drc_index);
@@ -468,7 +485,7 @@ static int dlpar_memory_remove_by_index(u32 drc_index)
for_each_drmem_lmb(lmb) {
if (lmb->drc_index == drc_index) {
lmb_found = 1;
- rc = dlpar_remove_lmb(lmb);
+ rc = dlpar_remove_lmb(lmb, true);
if (!rc)
dlpar_release_drc(lmb->drc_index);
@@ -493,6 +510,7 @@ 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;
+ bool dt_update = false;
pr_info("Attempting to hot-remove %u LMB(s) at %x\n",
lmbs_to_remove, drc_index);
@@ -519,7 +537,9 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
if (!(lmb->flags & DRCONF_MEM_ASSIGNED))
continue;
- rc = dlpar_remove_lmb(lmb);
+ if (lmb == end_lmb)
+ dt_update = true;
+ rc = dlpar_remove_lmb(lmb, dt_update);
if (rc)
break;
@@ -527,14 +547,17 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
}
if (rc) {
- pr_err("Memory indexed-count-remove failed, adding any removed LMBs\n");
+ bool rollback_dt_update = false;
+ pr_err("Memory indexed-count-remove failed, adding any removed LMBs\n");
for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
if (!drmem_lmb_reserved(lmb))
continue;
-
- rc = dlpar_add_lmb(lmb);
+ /* Since in removing path, dt is only updated if lmb == end_lmb */
+ if (lmb == end_lmb)
+ rollback_dt_update = true;
+ rc = dlpar_add_lmb(lmb, rollback_dt_update);
if (rc)
pr_err("Failed to add LMB, drc index %x\n",
lmb->drc_index);
@@ -572,7 +595,7 @@ static inline int dlpar_memory_remove(struct pseries_hp_errorlog *hp_elog)
{
return -EOPNOTSUPP;
}
-static int dlpar_remove_lmb(struct drmem_lmb *lmb)
+static int dlpar_remove_lmb(struct drmem_lmb *lmb, bool dt_update)
{
return -EOPNOTSUPP;
}
@@ -591,10 +614,10 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index)
}
#endif /* CONFIG_MEMORY_HOTREMOVE */
-static int dlpar_add_lmb(struct drmem_lmb *lmb)
+static int dlpar_add_lmb(struct drmem_lmb *lmb, bool dt_update)
{
unsigned long block_sz;
- int rc;
+ int rc, ret;
if (lmb->flags & DRCONF_MEM_ASSIGNED)
return -EINVAL;
@@ -607,6 +630,11 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
lmb_set_nid(lmb);
lmb->flags |= DRCONF_MEM_ASSIGNED;
+ if (dt_update) {
+ ret = drmem_update_dt();
+ if (ret)
+ pr_warn("%s fail to update dt, but continue\n", __func__);
+ }
block_sz = memory_block_size_bytes();
In the case the call to __add_memory is failing, the flag DRCONF_MEM_ASSIGNED
should be cleared as I mentioned in your previous patch. In addition to this,
the DT should be updated, or the caller should manage that but that will be hard
since it doesn't know where the error happened in this function.
@@ -625,7 +653,11 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
invalidate_lmb_associativity_index(lmb);
lmb_clear_nid(lmb);
lmb->flags &= ~DRCONF_MEM_ASSIGNED;
-
+ if (dt_update) {
+ ret = drmem_update_dt();
+ if (ret)
+ pr_warn("%s fail to update dt during rollback, but continue\n", __func__);
+ }
__remove_memory(nid, base_addr, block_sz);
}
@@ -638,6 +670,7 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
int lmbs_available = 0;
int lmbs_added = 0;
int rc;
+ bool dt_update = false;
pr_info("Attempting to hot-add %d LMB(s)\n", lmbs_to_add);
@@ -664,7 +697,7 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
if (rc)
continue;
- rc = dlpar_add_lmb(lmb);
+ rc = dlpar_add_lmb(lmb, dt_update);
if (rc) {
dlpar_release_drc(lmb->drc_index);
continue;
@@ -678,16 +711,23 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
lmbs_added++;
if (lmbs_added == lmbs_to_add)
break;
+ else if (lmbs_added == lmbs_to_add - 1)
+ dt_update = true;
In the case the number of LMB to add is 1, dt_update is never set to true, and
the device tree is never updated. You need to set dt_update to true earlier in
the loop block.
}
if (lmbs_added != lmbs_to_add) {
+ bool rollback_dt_update = false;
+
pr_err("Memory hot-add failed, removing any added LMBs\n");
for_each_drmem_lmb(lmb) {
if (!drmem_lmb_reserved(lmb))
continue;
- rc = dlpar_remove_lmb(lmb);
+ if (--lmbs_added == 0 && dt_update)
+ rollback_dt_update = true;
That test may have to be review to deal with error during the last LMB addition,
the DT may have been updated before __add_memory() is failing in
dlpar_add_lmb(). In that case, lmbs_added == 0 and that branch is not covered.
That's not an issue if dlpar_add_lmb() is handling that case (see my comment above).
+
+ rc = dlpar_remove_lmb(lmb, rollback_dt_update);
if (rc)
pr_err("Failed to remove LMB, drc index %x\n",
lmb->drc_index);
@@ -725,7 +765,7 @@ static int dlpar_memory_add_by_index(u32 drc_index)
lmb_found = 1;
rc = dlpar_acquire_drc(lmb->drc_index);
if (!rc) {
- rc = dlpar_add_lmb(lmb);
+ rc = dlpar_add_lmb(lmb, true);
if (rc)
dlpar_release_drc(lmb->drc_index);
}
@@ -751,6 +791,7 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32 drc_index)
struct drmem_lmb *lmb, *start_lmb, *end_lmb;
int lmbs_available = 0;
int rc;
+ bool dt_update = false;
pr_info("Attempting to hot-add %u LMB(s) at index %x\n",
lmbs_to_add, drc_index);
@@ -781,7 +822,9 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32 drc_index)
if (rc)
break;
- rc = dlpar_add_lmb(lmb);
+ if (lmb == end_lmb)
+ dt_update = true;
+ rc = dlpar_add_lmb(lmb, dt_update);
if (rc) {
dlpar_release_drc(lmb->drc_index);
break;
@@ -794,10 +837,14 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32 drc_index)
pr_err("Memory indexed-count-add failed, removing any added LMBs\n");
for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
+ bool rollback_dt_update = false;
+
if (!drmem_lmb_reserved(lmb))
continue;
- rc = dlpar_remove_lmb(lmb);
+ if (lmb == end_lmb)
+ rollback_dt_update = true;
+ rc = dlpar_remove_lmb(lmb, rollback_dt_update);
if (rc)
pr_err("Failed to remove LMB, drc index %x\n",
lmb->drc_index);
@@ -877,9 +924,6 @@ int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
break;
}
- if (!rc)
- rc = drmem_update_dt();
-
unlock_device_hotplug();
return rc;
}
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