* [PATCH 0/3] CPU DLPAR/hotplug for v5.16
@ 2021-09-20 13:55 Nathan Lynch
2021-09-20 13:55 ` [PATCH 1/3] powerpc/pseries/cpuhp: cache node corrections Nathan Lynch
` (2 more replies)
0 siblings, 3 replies; 11+ messages in thread
From: Nathan Lynch @ 2021-09-20 13:55 UTC (permalink / raw)
To: linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar, danielhb413
Fixes for some vintage bugs in handling cache node addition and removal, a
miscellaneous BUG->WARN conversion, and removal of the fragile "by count"
CPU DLPAR code that probably has no users.
Nathan Lynch (3):
powerpc/pseries/cpuhp: cache node corrections
powerpc/cpuhp: BUG -> WARN conversion in offline path
powerpc/pseries/cpuhp: delete add/remove_by_count code
arch/powerpc/kernel/sysfs.c | 3 +-
arch/powerpc/platforms/pseries/hotplug-cpu.c | 290 +++++--------------
2 files changed, 74 insertions(+), 219 deletions(-)
--
2.31.1
^ permalink raw reply [flat|nested] 11+ messages in thread* [PATCH 1/3] powerpc/pseries/cpuhp: cache node corrections 2021-09-20 13:55 [PATCH 0/3] CPU DLPAR/hotplug for v5.16 Nathan Lynch @ 2021-09-20 13:55 ` Nathan Lynch 2021-09-20 23:59 ` Daniel Henrique Barboza 2021-09-20 13:55 ` [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path Nathan Lynch 2021-09-20 13:55 ` [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code Nathan Lynch 2 siblings, 1 reply; 11+ messages in thread From: Nathan Lynch @ 2021-09-20 13:55 UTC (permalink / raw) To: linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar, danielhb413 On pseries, cache nodes in the device tree can be added and removed by the CPU DLPAR code as well as the partition migration (mobility) code. PowerVM partitions in dedicated processor mode typically have L2 and L3 cache nodes. The CPU DLPAR code has the following shortcomings: * Cache nodes returned as siblings of a new CPU node by ibm,configure-connector are silently discarded; only the CPU node is added to the device tree. * Cache nodes which become unreferenced in the processor removal path are not removed from the device tree. This can lead to duplicate nodes when the post-migration device tree update code replaces cache nodes. This is long-standing behavior. Presumably it has gone mostly unnoticed because the two bugs have the property of obscuring each other in common simple scenarios (e.g. remove a CPU and add it back). Likely you'd notice only if you cared to inspect the device tree or the sysfs cacheinfo information. Booted with two processors: $ pwd /sys/firmware/devicetree/base/cpus $ ls -1d */ l2-cache@2010/ l2-cache@2011/ l3-cache@3110/ l3-cache@3111/ PowerPC,POWER9@0/ PowerPC,POWER9@8/ $ lsprop */l2-cache l2-cache@2010/l2-cache 00003110 (12560) l2-cache@2011/l2-cache 00003111 (12561) PowerPC,POWER9@0/l2-cache 00002010 (8208) PowerPC,POWER9@8/l2-cache 00002011 (8209) $ ls /sys/devices/system/cpu/cpu0/cache/ index0 index1 index2 index3 After DLPAR-adding PowerPC,POWER9@10, we see that its associated cache nodes are absent, its threads' L2+L3 cacheinfo is unpopulated, and it is missing a cache level in its sched domain hierarchy: $ ls -1d */ l2-cache@2010/ l2-cache@2011/ l3-cache@3110/ l3-cache@3111/ PowerPC,POWER9@0/ PowerPC,POWER9@10/ PowerPC,POWER9@8/ $ lsprop PowerPC\,POWER9@10/l2-cache PowerPC,POWER9@10/l2-cache 00002012 (8210) $ ls /sys/devices/system/cpu/cpu16/cache/ index0 index1 $ grep . /sys/kernel/debug/sched/domains/cpu{0,8,16}/domain*/name /sys/kernel/debug/sched/domains/cpu0/domain0/name:SMT /sys/kernel/debug/sched/domains/cpu0/domain1/name:CACHE /sys/kernel/debug/sched/domains/cpu0/domain2/name:DIE /sys/kernel/debug/sched/domains/cpu8/domain0/name:SMT /sys/kernel/debug/sched/domains/cpu8/domain1/name:CACHE /sys/kernel/debug/sched/domains/cpu8/domain2/name:DIE /sys/kernel/debug/sched/domains/cpu16/domain0/name:SMT /sys/kernel/debug/sched/domains/cpu16/domain1/name:DIE When removing PowerPC,POWER9@8, we see that its cache nodes are left behind: $ ls -1d */ l2-cache@2010/ l2-cache@2011/ l3-cache@3110/ l3-cache@3111/ PowerPC,POWER9@0/ When DLPAR is combined with VM migration, we can get duplicate nodes. E.g. removing one processor, then migrating, adding a processor, and then migrating again can result in warnings from the OF core during post-migration device tree updates: Duplicate name in cpus, renamed to "l2-cache@2011#1" Duplicate name in cpus, renamed to "l3-cache@3111#1" and nodes with duplicated phandles in the tree, making lookup behavior unpredictable: $ lsprop l[23]-cache@*/ibm,phandle l2-cache@2010/ibm,phandle 00002010 (8208) l2-cache@2011#1/ibm,phandle 00002011 (8209) l2-cache@2011/ibm,phandle 00002011 (8209) l3-cache@3110/ibm,phandle 00003110 (12560) l3-cache@3111#1/ibm,phandle 00003111 (12561) l3-cache@3111/ibm,phandle 00003111 (12561) Address these issues by: * Correctly processing siblings of the node returned from dlpar_configure_connector(). * Removing cache nodes in the CPU remove path when it can be determined that they are not associated with other CPUs or caches. Use the of_changeset API in both cases, which allows us to keep the error handling in this code from becoming more complex while ensuring that the device tree cannot become inconsistent. Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> Fixes: ac71380 ("powerpc/pseries: Add CPU dlpar remove functionality") Fixes: 90edf18 ("powerpc/pseries: Add CPU dlpar add functionality") --- arch/powerpc/platforms/pseries/hotplug-cpu.c | 72 +++++++++++++++++++- 1 file changed, 70 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c index d646c22e94ab..87a0fbe9cf12 100644 --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c @@ -521,6 +521,27 @@ static bool valid_cpu_drc_index(struct device_node *parent, u32 drc_index) return found; } +static int pseries_cpuhp_attach_nodes(struct device_node *dn) +{ + struct of_changeset cs; + int ret; + + /* + * This device node is unattached but may have siblings; open-code the + * traversal. + */ + for (of_changeset_init(&cs); dn != NULL; dn = dn->sibling) { + ret = of_changeset_attach_node(&cs, dn); + if (ret) + goto out; + } + + ret = of_changeset_apply(&cs); +out: + of_changeset_destroy(&cs); + return ret; +} + static ssize_t dlpar_cpu_add(u32 drc_index) { struct device_node *dn, *parent; @@ -563,7 +584,7 @@ static ssize_t dlpar_cpu_add(u32 drc_index) return -EINVAL; } - rc = dlpar_attach_node(dn, parent); + rc = pseries_cpuhp_attach_nodes(dn); /* Regardless we are done with parent now */ of_node_put(parent); @@ -600,6 +621,53 @@ static ssize_t dlpar_cpu_add(u32 drc_index) return rc; } +static unsigned int pseries_cpuhp_cache_use_count(const struct device_node *cachedn) +{ + unsigned int use_count = 0; + struct device_node *dn; + + WARN_ON(!of_node_is_type(cachedn, "cache")); + + for_each_of_cpu_node(dn) { + if (of_find_next_cache_node(dn) == cachedn) + use_count++; + } + + for_each_node_by_type(dn, "cache") { + if (of_find_next_cache_node(dn) == cachedn) + use_count++; + } + + return use_count; +} + +static int pseries_cpuhp_detach_nodes(struct device_node *cpudn) +{ + struct device_node *dn; + struct of_changeset cs; + int ret = 0; + + of_changeset_init(&cs); + ret = of_changeset_detach_node(&cs, cpudn); + if (ret) + goto out; + + dn = cpudn; + while ((dn = of_find_next_cache_node(dn))) { + if (pseries_cpuhp_cache_use_count(dn) > 1) + break; + + ret = of_changeset_detach_node(&cs, dn); + if (ret) + goto out; + } + + ret = of_changeset_apply(&cs); +out: + of_changeset_destroy(&cs); + return ret; +} + static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index) { int rc; @@ -621,7 +689,7 @@ static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index) return rc; } - rc = dlpar_detach_node(dn); + rc = pseries_cpuhp_detach_nodes(dn); if (rc) { int saved_rc = rc; -- 2.31.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH 1/3] powerpc/pseries/cpuhp: cache node corrections 2021-09-20 13:55 ` [PATCH 1/3] powerpc/pseries/cpuhp: cache node corrections Nathan Lynch @ 2021-09-20 23:59 ` Daniel Henrique Barboza 0 siblings, 0 replies; 11+ messages in thread From: Daniel Henrique Barboza @ 2021-09-20 23:59 UTC (permalink / raw) To: Nathan Lynch, linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar On 9/20/21 10:55, Nathan Lynch wrote: > On pseries, cache nodes in the device tree can be added and removed by the > CPU DLPAR code as well as the partition migration (mobility) code. PowerVM > partitions in dedicated processor mode typically have L2 and L3 cache > nodes. > > The CPU DLPAR code has the following shortcomings: > > * Cache nodes returned as siblings of a new CPU node by > ibm,configure-connector are silently discarded; only the CPU node is > added to the device tree. > > * Cache nodes which become unreferenced in the processor removal path are > not removed from the device tree. This can lead to duplicate nodes when > the post-migration device tree update code replaces cache nodes. > > This is long-standing behavior. Presumably it has gone mostly unnoticed > because the two bugs have the property of obscuring each other in common > simple scenarios (e.g. remove a CPU and add it back). Likely you'd notice > only if you cared to inspect the device tree or the sysfs cacheinfo > information. > > Booted with two processors: > > $ pwd > /sys/firmware/devicetree/base/cpus > $ ls -1d */ > l2-cache@2010/ > l2-cache@2011/ > l3-cache@3110/ > l3-cache@3111/ > PowerPC,POWER9@0/ > PowerPC,POWER9@8/ > $ lsprop */l2-cache > l2-cache@2010/l2-cache > 00003110 (12560) > l2-cache@2011/l2-cache > 00003111 (12561) > PowerPC,POWER9@0/l2-cache > 00002010 (8208) > PowerPC,POWER9@8/l2-cache > 00002011 (8209) > $ ls /sys/devices/system/cpu/cpu0/cache/ > index0 index1 index2 index3 > > After DLPAR-adding PowerPC,POWER9@10, we see that its associated cache > nodes are absent, its threads' L2+L3 cacheinfo is unpopulated, and it is > missing a cache level in its sched domain hierarchy: > > $ ls -1d */ > l2-cache@2010/ > l2-cache@2011/ > l3-cache@3110/ > l3-cache@3111/ > PowerPC,POWER9@0/ > PowerPC,POWER9@10/ > PowerPC,POWER9@8/ > $ lsprop PowerPC\,POWER9@10/l2-cache > PowerPC,POWER9@10/l2-cache > 00002012 (8210) > $ ls /sys/devices/system/cpu/cpu16/cache/ > index0 index1 > $ grep . /sys/kernel/debug/sched/domains/cpu{0,8,16}/domain*/name > /sys/kernel/debug/sched/domains/cpu0/domain0/name:SMT > /sys/kernel/debug/sched/domains/cpu0/domain1/name:CACHE > /sys/kernel/debug/sched/domains/cpu0/domain2/name:DIE > /sys/kernel/debug/sched/domains/cpu8/domain0/name:SMT > /sys/kernel/debug/sched/domains/cpu8/domain1/name:CACHE > /sys/kernel/debug/sched/domains/cpu8/domain2/name:DIE > /sys/kernel/debug/sched/domains/cpu16/domain0/name:SMT > /sys/kernel/debug/sched/domains/cpu16/domain1/name:DIE > > When removing PowerPC,POWER9@8, we see that its cache nodes are left > behind: > > $ ls -1d */ > l2-cache@2010/ > l2-cache@2011/ > l3-cache@3110/ > l3-cache@3111/ > PowerPC,POWER9@0/ > > When DLPAR is combined with VM migration, we can get duplicate nodes. E.g. > removing one processor, then migrating, adding a processor, and then > migrating again can result in warnings from the OF core during > post-migration device tree updates: > > Duplicate name in cpus, renamed to "l2-cache@2011#1" > Duplicate name in cpus, renamed to "l3-cache@3111#1" > > and nodes with duplicated phandles in the tree, making lookup behavior > unpredictable: > > $ lsprop l[23]-cache@*/ibm,phandle > l2-cache@2010/ibm,phandle > 00002010 (8208) > l2-cache@2011#1/ibm,phandle > 00002011 (8209) > l2-cache@2011/ibm,phandle > 00002011 (8209) > l3-cache@3110/ibm,phandle > 00003110 (12560) > l3-cache@3111#1/ibm,phandle > 00003111 (12561) > l3-cache@3111/ibm,phandle > 00003111 (12561) > > Address these issues by: > > * Correctly processing siblings of the node returned from > dlpar_configure_connector(). > * Removing cache nodes in the CPU remove path when it can be determined > that they are not associated with other CPUs or caches. > > Use the of_changeset API in both cases, which allows us to keep the error > handling in this code from becoming more complex while ensuring that the > device tree cannot become inconsistent. > > Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> > Fixes: ac71380 ("powerpc/pseries: Add CPU dlpar remove functionality") > Fixes: 90edf18 ("powerpc/pseries: Add CPU dlpar add functionality") > --- > arch/powerpc/platforms/pseries/hotplug-cpu.c | 72 +++++++++++++++++++- > 1 file changed, 70 insertions(+), 2 deletions(-) Tested with a QEMU pseries guest, multiple CPU add/removals of the same CPU, and no issues found with these new pseries_cpuhp* functions. Code LGTM as well. Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com> > > diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c > index d646c22e94ab..87a0fbe9cf12 100644 > --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c > +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c > @@ -521,6 +521,27 @@ static bool valid_cpu_drc_index(struct device_node *parent, u32 drc_index) > return found; > } > > +static int pseries_cpuhp_attach_nodes(struct device_node *dn) > +{ > + struct of_changeset cs; > + int ret; > + > + /* > + * This device node is unattached but may have siblings; open-code the > + * traversal. > + */ > + for (of_changeset_init(&cs); dn != NULL; dn = dn->sibling) { > + ret = of_changeset_attach_node(&cs, dn); > + if (ret) > + goto out; > + } > + > + ret = of_changeset_apply(&cs); > +out: > + of_changeset_destroy(&cs); > + return ret; > +} > + > static ssize_t dlpar_cpu_add(u32 drc_index) > { > struct device_node *dn, *parent; > @@ -563,7 +584,7 @@ static ssize_t dlpar_cpu_add(u32 drc_index) > return -EINVAL; > } > > - rc = dlpar_attach_node(dn, parent); > + rc = pseries_cpuhp_attach_nodes(dn); > > /* Regardless we are done with parent now */ > of_node_put(parent); > @@ -600,6 +621,53 @@ static ssize_t dlpar_cpu_add(u32 drc_index) > return rc; > } > > +static unsigned int pseries_cpuhp_cache_use_count(const struct device_node *cachedn) > +{ > + unsigned int use_count = 0; > + struct device_node *dn; > + > + WARN_ON(!of_node_is_type(cachedn, "cache")); > + > + for_each_of_cpu_node(dn) { > + if (of_find_next_cache_node(dn) == cachedn) > + use_count++; > + } > + > + for_each_node_by_type(dn, "cache") { > + if (of_find_next_cache_node(dn) == cachedn) > + use_count++; > + } > + > + return use_count; > +} > + > +static int pseries_cpuhp_detach_nodes(struct device_node *cpudn) > +{ > + struct device_node *dn; > + struct of_changeset cs; > + int ret = 0; > + > + of_changeset_init(&cs); > + ret = of_changeset_detach_node(&cs, cpudn); > + if (ret) > + goto out; > + > + dn = cpudn; > + while ((dn = of_find_next_cache_node(dn))) { > + if (pseries_cpuhp_cache_use_count(dn) > 1) > + break; > + > + ret = of_changeset_detach_node(&cs, dn); > + if (ret) > + goto out; > + } > + > + ret = of_changeset_apply(&cs); > +out: > + of_changeset_destroy(&cs); > + return ret; > +} > + > static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index) > { > int rc; > @@ -621,7 +689,7 @@ static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index) > return rc; > } > > - rc = dlpar_detach_node(dn); > + rc = pseries_cpuhp_detach_nodes(dn); > if (rc) { > int saved_rc = rc; > > ^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path 2021-09-20 13:55 [PATCH 0/3] CPU DLPAR/hotplug for v5.16 Nathan Lynch 2021-09-20 13:55 ` [PATCH 1/3] powerpc/pseries/cpuhp: cache node corrections Nathan Lynch @ 2021-09-20 13:55 ` Nathan Lynch 2021-09-20 14:26 ` Christophe Leroy 2021-09-21 0:05 ` Daniel Henrique Barboza 2021-09-20 13:55 ` [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code Nathan Lynch 2 siblings, 2 replies; 11+ messages in thread From: Nathan Lynch @ 2021-09-20 13:55 UTC (permalink / raw) To: linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar, danielhb413 If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU that isn't marked hotpluggable, we can emit a warning and return an appropriate error instead of crashing. Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> --- arch/powerpc/kernel/sysfs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index defecb3b1b15..08d8072d6e7a 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -928,7 +928,8 @@ static int unregister_cpu_online(unsigned int cpu) struct device_attribute *attrs, *pmc_attrs; int i, nattrs; - BUG_ON(!c->hotpluggable); + if (WARN_RATELIMIT(!c->hotpluggable, "cpu %d can't be offlined\n", cpu)) + return -EBUSY; #ifdef CONFIG_PPC64 if (cpu_has_feature(CPU_FTR_SMT)) -- 2.31.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path 2021-09-20 13:55 ` [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path Nathan Lynch @ 2021-09-20 14:26 ` Christophe Leroy 2021-09-20 14:39 ` Nathan Lynch 2021-09-21 0:05 ` Daniel Henrique Barboza 1 sibling, 1 reply; 11+ messages in thread From: Christophe Leroy @ 2021-09-20 14:26 UTC (permalink / raw) To: Nathan Lynch, linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar, danielhb413 Le 20/09/2021 à 15:55, Nathan Lynch a écrit : > If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU > that isn't marked hotpluggable, we can emit a warning and return an > appropriate error instead of crashing. Is it only a bug situation, or is it something that can happen in real life ? If it can happen in real life, kernels with panic_on_warn will still be impacted. > > Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> > --- > arch/powerpc/kernel/sysfs.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > index defecb3b1b15..08d8072d6e7a 100644 > --- a/arch/powerpc/kernel/sysfs.c > +++ b/arch/powerpc/kernel/sysfs.c > @@ -928,7 +928,8 @@ static int unregister_cpu_online(unsigned int cpu) > struct device_attribute *attrs, *pmc_attrs; > int i, nattrs; > > - BUG_ON(!c->hotpluggable); > + if (WARN_RATELIMIT(!c->hotpluggable, "cpu %d can't be offlined\n", cpu)) > + return -EBUSY; > > #ifdef CONFIG_PPC64 > if (cpu_has_feature(CPU_FTR_SMT)) > ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path 2021-09-20 14:26 ` Christophe Leroy @ 2021-09-20 14:39 ` Nathan Lynch 0 siblings, 0 replies; 11+ messages in thread From: Nathan Lynch @ 2021-09-20 14:39 UTC (permalink / raw) To: Christophe Leroy, linuxppc-dev; +Cc: danielhb413, tyreld, ldufour, aneesh.kumar Christophe Leroy <christophe.leroy@csgroup.eu> writes: > Le 20/09/2021 à 15:55, Nathan Lynch a écrit : >> If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU >> that isn't marked hotpluggable, we can emit a warning and return an >> appropriate error instead of crashing. > > Is it only a bug situation, or is it something that can happen in real > life ? > > If it can happen in real life, kernels with panic_on_warn will still be > impacted. I only found this by inspection, and it can happen only due to a bug in CPU device registration at boot. The flag must not be set if the platform or CPU can't support going offline. ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path 2021-09-20 13:55 ` [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path Nathan Lynch 2021-09-20 14:26 ` Christophe Leroy @ 2021-09-21 0:05 ` Daniel Henrique Barboza 1 sibling, 0 replies; 11+ messages in thread From: Daniel Henrique Barboza @ 2021-09-21 0:05 UTC (permalink / raw) To: Nathan Lynch, linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar On 9/20/21 10:55, Nathan Lynch wrote: > If, due to bugs elsewhere, we get into unregister_cpu_online() with a CPU > that isn't marked hotpluggable, we can emit a warning and return an > appropriate error instead of crashing. > > Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> > --- As mentioned by Christophe this will not solve the crash for kernels with panic_on_warn, but at least it will panic with a clearer message on those and will not panic for everyone else. Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> > arch/powerpc/kernel/sysfs.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c > index defecb3b1b15..08d8072d6e7a 100644 > --- a/arch/powerpc/kernel/sysfs.c > +++ b/arch/powerpc/kernel/sysfs.c > @@ -928,7 +928,8 @@ static int unregister_cpu_online(unsigned int cpu) > struct device_attribute *attrs, *pmc_attrs; > int i, nattrs; > > - BUG_ON(!c->hotpluggable); > + if (WARN_RATELIMIT(!c->hotpluggable, "cpu %d can't be offlined\n", cpu)) > + return -EBUSY; > > #ifdef CONFIG_PPC64 > if (cpu_has_feature(CPU_FTR_SMT)) > ^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code 2021-09-20 13:55 [PATCH 0/3] CPU DLPAR/hotplug for v5.16 Nathan Lynch 2021-09-20 13:55 ` [PATCH 1/3] powerpc/pseries/cpuhp: cache node corrections Nathan Lynch 2021-09-20 13:55 ` [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path Nathan Lynch @ 2021-09-20 13:55 ` Nathan Lynch 2021-09-20 21:50 ` kernel test robot 2021-09-21 0:18 ` Daniel Henrique Barboza 2 siblings, 2 replies; 11+ messages in thread From: Nathan Lynch @ 2021-09-20 13:55 UTC (permalink / raw) To: linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar, danielhb413 The core DLPAR code supports two actions (add and remove) and three subtypes of action: * By DRC index: the action is attempted on a single specified resource. This is the usual case for processors. * By indexed count: the action is attempted on a range of resources beginning at the specified index. This is implemented only by the memory DLPAR code. * By count: the lower layer (CPU or memory) is responsible for locating the specified number of resources to which the action can be applied. I cannot find any evidence of the "by count" subtype being used by drmgr or qemu for processors. And when I try to exercise this code, the add case does not work: $ ppc64_cpu --smt ; nproc SMT=8 24 $ printf "cpu remove count 2" > /sys/kernel/dlpar $ nproc 8 $ printf "cpu add count 2" > /sys/kernel/dlpar -bash: printf: write error: Invalid argument $ dmesg | tail -2 pseries-hotplug-cpu: Failed to find enough CPUs (1 of 2) to add dlpar: Could not handle DLPAR request "cpu add count 2" $ nproc 8 $ drmgr -c cpu -a -q 2 # this uses the by-index method Validating CPU DLPAR capability...yes. CPU 1 CPU 17 $ nproc 24 This is because find_drc_info_cpus_to_add() does not increment drc_index appropriately during its search. This is not hard to fix. But the _by_count() functions also have the property that they attempt to roll back all prior operations if the entire request cannot be satisfied, even though the rollback itself can encounter errors. It's not possible to provide transaction-like behavior at this level, and it's undesirable to have code that can only pretend to do that. Any users of these functions cannot know what the state of the system is in the error case. And the error paths are, to my knowledge, impossible to test without adding custom error injection code. Summary: * This code has not worked reliably since its introduction. * There is no evidence that it is used. * It contains questionable rollback behaviors in error paths which are difficult to test. So let's remove it. Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> Fixes: ac71380071d1 ("powerpc/pseries: Add CPU dlpar remove functionality") Fixes: 90edf184b9b7 ("powerpc/pseries: Add CPU dlpar add functionality") Fixes: b015f6bc9547 ("powerpc/pseries: Add cpu DLPAR support for drc-info property") --- arch/powerpc/platforms/pseries/hotplug-cpu.c | 218 +------------------ 1 file changed, 2 insertions(+), 216 deletions(-) diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c index 87a0fbe9cf12..768997261ce8 100644 --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c @@ -741,216 +741,6 @@ static int dlpar_cpu_remove_by_index(u32 drc_index) return rc; } -static int find_dlpar_cpus_to_remove(u32 *cpu_drcs, int cpus_to_remove) -{ - struct device_node *dn; - int cpus_found = 0; - int rc; - - /* We want to find cpus_to_remove + 1 CPUs to ensure we do not - * remove the last CPU. - */ - for_each_node_by_type(dn, "cpu") { - cpus_found++; - - if (cpus_found > cpus_to_remove) { - of_node_put(dn); - break; - } - - /* Note that cpus_found is always 1 ahead of the index - * into the cpu_drcs array, so we use cpus_found - 1 - */ - rc = of_property_read_u32(dn, "ibm,my-drc-index", - &cpu_drcs[cpus_found - 1]); - if (rc) { - pr_warn("Error occurred getting drc-index for %pOFn\n", - dn); - of_node_put(dn); - return -1; - } - } - - if (cpus_found < cpus_to_remove) { - pr_warn("Failed to find enough CPUs (%d of %d) to remove\n", - cpus_found, cpus_to_remove); - } else if (cpus_found == cpus_to_remove) { - pr_warn("Cannot remove all CPUs\n"); - } - - return cpus_found; -} - -static int dlpar_cpu_remove_by_count(u32 cpus_to_remove) -{ - u32 *cpu_drcs; - int cpus_found; - int cpus_removed = 0; - int i, rc; - - pr_debug("Attempting to hot-remove %d CPUs\n", cpus_to_remove); - - cpu_drcs = kcalloc(cpus_to_remove, sizeof(*cpu_drcs), GFP_KERNEL); - if (!cpu_drcs) - return -EINVAL; - - cpus_found = find_dlpar_cpus_to_remove(cpu_drcs, cpus_to_remove); - if (cpus_found <= cpus_to_remove) { - kfree(cpu_drcs); - return -EINVAL; - } - - for (i = 0; i < cpus_to_remove; i++) { - rc = dlpar_cpu_remove_by_index(cpu_drcs[i]); - if (rc) - break; - - cpus_removed++; - } - - if (cpus_removed != cpus_to_remove) { - pr_warn("CPU hot-remove failed, adding back removed CPUs\n"); - - for (i = 0; i < cpus_removed; i++) - dlpar_cpu_add(cpu_drcs[i]); - - rc = -EINVAL; - } else { - rc = 0; - } - - kfree(cpu_drcs); - return rc; -} - -static int find_drc_info_cpus_to_add(struct device_node *cpus, - struct property *info, - u32 *cpu_drcs, u32 cpus_to_add) -{ - struct of_drc_info drc; - const __be32 *value; - u32 count, drc_index; - int cpus_found = 0; - int i, j; - - if (!info) - return -1; - - value = of_prop_next_u32(info, NULL, &count); - if (value) - value++; - - for (i = 0; i < count; i++) { - of_read_drc_info_cell(&info, &value, &drc); - if (strncmp(drc.drc_type, "CPU", 3)) - break; - - drc_index = drc.drc_index_start; - for (j = 0; j < drc.num_sequential_elems; j++) { - if (dlpar_cpu_exists(cpus, drc_index)) - continue; - - cpu_drcs[cpus_found++] = drc_index; - - if (cpus_found == cpus_to_add) - return cpus_found; - - drc_index += drc.sequential_inc; - } - } - - return cpus_found; -} - -static int find_drc_index_cpus_to_add(struct device_node *cpus, - u32 *cpu_drcs, u32 cpus_to_add) -{ - int cpus_found = 0; - int index, rc; - u32 drc_index; - - /* Search the ibm,drc-indexes array for possible CPU drcs to - * add. Note that the format of the ibm,drc-indexes array is - * the number of entries in the array followed by the array - * of drc values so we start looking at index = 1. - */ - index = 1; - while (cpus_found < cpus_to_add) { - rc = of_property_read_u32_index(cpus, "ibm,drc-indexes", - index++, &drc_index); - - if (rc) - break; - - if (dlpar_cpu_exists(cpus, drc_index)) - continue; - - cpu_drcs[cpus_found++] = drc_index; - } - - return cpus_found; -} - -static int dlpar_cpu_add_by_count(u32 cpus_to_add) -{ - struct device_node *parent; - struct property *info; - u32 *cpu_drcs; - int cpus_added = 0; - int cpus_found; - int i, rc; - - pr_debug("Attempting to hot-add %d CPUs\n", cpus_to_add); - - cpu_drcs = kcalloc(cpus_to_add, sizeof(*cpu_drcs), GFP_KERNEL); - if (!cpu_drcs) - return -EINVAL; - - parent = of_find_node_by_path("/cpus"); - if (!parent) { - pr_warn("Could not find CPU root node in device tree\n"); - kfree(cpu_drcs); - return -1; - } - - info = of_find_property(parent, "ibm,drc-info", NULL); - if (info) - cpus_found = find_drc_info_cpus_to_add(parent, info, cpu_drcs, cpus_to_add); - else - cpus_found = find_drc_index_cpus_to_add(parent, cpu_drcs, cpus_to_add); - - of_node_put(parent); - - if (cpus_found < cpus_to_add) { - pr_warn("Failed to find enough CPUs (%d of %d) to add\n", - cpus_found, cpus_to_add); - kfree(cpu_drcs); - return -EINVAL; - } - - for (i = 0; i < cpus_to_add; i++) { - rc = dlpar_cpu_add(cpu_drcs[i]); - if (rc) - break; - - cpus_added++; - } - - if (cpus_added < cpus_to_add) { - pr_warn("CPU hot-add failed, removing any added CPUs\n"); - - for (i = 0; i < cpus_added; i++) - dlpar_cpu_remove_by_index(cpu_drcs[i]); - - rc = -EINVAL; - } else { - rc = 0; - } - - kfree(cpu_drcs); - return rc; -} - int dlpar_cpu(struct pseries_hp_errorlog *hp_elog) { u32 count, drc_index; @@ -963,9 +753,7 @@ int dlpar_cpu(struct pseries_hp_errorlog *hp_elog) switch (hp_elog->action) { case PSERIES_HP_ELOG_ACTION_REMOVE: - if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT) - rc = dlpar_cpu_remove_by_count(count); - else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) { + if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) { rc = dlpar_cpu_remove_by_index(drc_index); /* * Setting the isolation state of an UNISOLATED/CONFIGURED @@ -979,9 +767,7 @@ int dlpar_cpu(struct pseries_hp_errorlog *hp_elog) rc = -EINVAL; break; case PSERIES_HP_ELOG_ACTION_ADD: - if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT) - rc = dlpar_cpu_add_by_count(count); - else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) + if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) rc = dlpar_cpu_add(drc_index); else rc = -EINVAL; -- 2.31.1 ^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code 2021-09-20 13:55 ` [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code Nathan Lynch @ 2021-09-20 21:50 ` kernel test robot 2021-09-21 0:18 ` Daniel Henrique Barboza 1 sibling, 0 replies; 11+ messages in thread From: kernel test robot @ 2021-09-20 21:50 UTC (permalink / raw) To: Nathan Lynch, linuxppc-dev Cc: danielhb413, tyreld, ldufour, kbuild-all, aneesh.kumar [-- Attachment #1: Type: text/plain, Size: 5199 bytes --] Hi Nathan, Thank you for the patch! Yet something to improve: [auto build test ERROR on powerpc/next] [also build test ERROR on linus/master v5.15-rc2 next-20210920] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch] url: https://github.com/0day-ci/linux/commits/Nathan-Lynch/CPU-DLPAR-hotplug-for-v5-16/20210920-215907 base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next config: powerpc-allmodconfig (attached as .config) compiler: powerpc64-linux-gcc (GCC) 11.2.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://github.com/0day-ci/linux/commit/72ea4c8a5398a4a72da34051a66f260ab0154f57 git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Nathan-Lynch/CPU-DLPAR-hotplug-for-v5-16/20210920-215907 git checkout 72ea4c8a5398a4a72da34051a66f260ab0154f57 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=powerpc If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp@intel.com> All errors (new ones prefixed by >>): arch/powerpc/platforms/pseries/hotplug-cpu.c: In function 'dlpar_cpu': >> arch/powerpc/platforms/pseries/hotplug-cpu.c:746:13: error: variable 'count' set but not used [-Werror=unused-but-set-variable] 746 | u32 count, drc_index; | ^~~~~ cc1: all warnings being treated as errors vim +/count +746 arch/powerpc/platforms/pseries/hotplug-cpu.c ac71380071d19d Nathan Fontenot 2015-12-16 743 ac71380071d19d Nathan Fontenot 2015-12-16 744 int dlpar_cpu(struct pseries_hp_errorlog *hp_elog) ac71380071d19d Nathan Fontenot 2015-12-16 745 { ac71380071d19d Nathan Fontenot 2015-12-16 @746 u32 count, drc_index; ac71380071d19d Nathan Fontenot 2015-12-16 747 int rc; ac71380071d19d Nathan Fontenot 2015-12-16 748 ac71380071d19d Nathan Fontenot 2015-12-16 749 count = hp_elog->_drc_u.drc_count; ac71380071d19d Nathan Fontenot 2015-12-16 750 drc_index = hp_elog->_drc_u.drc_index; ac71380071d19d Nathan Fontenot 2015-12-16 751 ac71380071d19d Nathan Fontenot 2015-12-16 752 lock_device_hotplug(); ac71380071d19d Nathan Fontenot 2015-12-16 753 ac71380071d19d Nathan Fontenot 2015-12-16 754 switch (hp_elog->action) { ac71380071d19d Nathan Fontenot 2015-12-16 755 case PSERIES_HP_ELOG_ACTION_REMOVE: 72ea4c8a5398a4 Nathan Lynch 2021-09-20 756 if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) { ac71380071d19d Nathan Fontenot 2015-12-16 757 rc = dlpar_cpu_remove_by_index(drc_index); 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 758 /* 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 759 * Setting the isolation state of an UNISOLATED/CONFIGURED 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 760 * device to UNISOLATE is a no-op, but the hypervisor can 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 761 * use it as a hint that the CPU removal failed. 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 762 */ 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 763 if (rc) 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 764 dlpar_unisolate_drc(drc_index); 29c9a2699e71a7 Daniel Henrique Barboza 2021-04-16 765 } ac71380071d19d Nathan Fontenot 2015-12-16 766 else ac71380071d19d Nathan Fontenot 2015-12-16 767 rc = -EINVAL; ac71380071d19d Nathan Fontenot 2015-12-16 768 break; 90edf184b9b727 Nathan Fontenot 2015-12-16 769 case PSERIES_HP_ELOG_ACTION_ADD: 72ea4c8a5398a4 Nathan Lynch 2021-09-20 770 if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) 90edf184b9b727 Nathan Fontenot 2015-12-16 771 rc = dlpar_cpu_add(drc_index); 90edf184b9b727 Nathan Fontenot 2015-12-16 772 else 90edf184b9b727 Nathan Fontenot 2015-12-16 773 rc = -EINVAL; 90edf184b9b727 Nathan Fontenot 2015-12-16 774 break; ac71380071d19d Nathan Fontenot 2015-12-16 775 default: ac71380071d19d Nathan Fontenot 2015-12-16 776 pr_err("Invalid action (%d) specified\n", hp_elog->action); ac71380071d19d Nathan Fontenot 2015-12-16 777 rc = -EINVAL; ac71380071d19d Nathan Fontenot 2015-12-16 778 break; ac71380071d19d Nathan Fontenot 2015-12-16 779 } ac71380071d19d Nathan Fontenot 2015-12-16 780 ac71380071d19d Nathan Fontenot 2015-12-16 781 unlock_device_hotplug(); ac71380071d19d Nathan Fontenot 2015-12-16 782 return rc; ac71380071d19d Nathan Fontenot 2015-12-16 783 } ac71380071d19d Nathan Fontenot 2015-12-16 784 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org [-- Attachment #2: .config.gz --] [-- Type: application/gzip, Size: 74041 bytes --] ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code 2021-09-20 13:55 ` [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code Nathan Lynch 2021-09-20 21:50 ` kernel test robot @ 2021-09-21 0:18 ` Daniel Henrique Barboza 2021-09-21 0:43 ` Nathan Lynch 1 sibling, 1 reply; 11+ messages in thread From: Daniel Henrique Barboza @ 2021-09-21 0:18 UTC (permalink / raw) To: Nathan Lynch, linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar On 9/20/21 10:55, Nathan Lynch wrote: > The core DLPAR code supports two actions (add and remove) and three > subtypes of action: > > * By DRC index: the action is attempted on a single specified resource. > This is the usual case for processors. > * By indexed count: the action is attempted on a range of resources > beginning at the specified index. This is implemented only by the memory > DLPAR code. > * By count: the lower layer (CPU or memory) is responsible for locating the > specified number of resources to which the action can be applied. > > I cannot find any evidence of the "by count" subtype being used by drmgr or > qemu for processors. And when I try to exercise this code, the add case > does not work: Just to clarify: did you check both CPU and memory cases and found out that the 'by count' subtype isn't used with CPUs, but drmgr has some cases in which 'by count' is used with LMBs? I'm asking because I worked with a part of the LMB removal code a few months ago, and got stuck in a situation in which the 'by count' and 'by indexed count' are similar enough to feel repetitive, but distinct enough to not be easily reduced into a single function. If drmgr wasn't using the 'by count' subtypes for LMBs that would be a good chance for more code redux. > > $ ppc64_cpu --smt ; nproc > SMT=8 > 24 > $ printf "cpu remove count 2" > /sys/kernel/dlpar > $ nproc > 8 > $ printf "cpu add count 2" > /sys/kernel/dlpar > -bash: printf: write error: Invalid argument > $ dmesg | tail -2 > pseries-hotplug-cpu: Failed to find enough CPUs (1 of 2) to add > dlpar: Could not handle DLPAR request "cpu add count 2" > $ nproc > 8 > $ drmgr -c cpu -a -q 2 # this uses the by-index method > Validating CPU DLPAR capability...yes. > CPU 1 > CPU 17 > $ nproc > 24 > > This is because find_drc_info_cpus_to_add() does not increment drc_index > appropriately during its search. > > This is not hard to fix. But the _by_count() functions also have the > property that they attempt to roll back all prior operations if the entire > request cannot be satisfied, even though the rollback itself can encounter > errors. It's not possible to provide transaction-like behavior at this > level, and it's undesirable to have code that can only pretend to do that. > Any users of these functions cannot know what the state of the system is in > the error case. And the error paths are, to my knowledge, impossible to > test without adding custom error injection code. > > Summary: > > * This code has not worked reliably since its introduction. > * There is no evidence that it is used. > * It contains questionable rollback behaviors in error paths which are > difficult to test. > > So let's remove it. > > Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> > Fixes: ac71380071d1 ("powerpc/pseries: Add CPU dlpar remove functionality") > Fixes: 90edf184b9b7 ("powerpc/pseries: Add CPU dlpar add functionality") > Fixes: b015f6bc9547 ("powerpc/pseries: Add cpu DLPAR support for drc-info property") > --- Tested with a QEMU pseries guest, no issues found. Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com> > arch/powerpc/platforms/pseries/hotplug-cpu.c | 218 +------------------ > 1 file changed, 2 insertions(+), 216 deletions(-) > > diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c > index 87a0fbe9cf12..768997261ce8 100644 > --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c > +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c > @@ -741,216 +741,6 @@ static int dlpar_cpu_remove_by_index(u32 drc_index) > return rc; > } > > -static int find_dlpar_cpus_to_remove(u32 *cpu_drcs, int cpus_to_remove) > -{ > - struct device_node *dn; > - int cpus_found = 0; > - int rc; > - > - /* We want to find cpus_to_remove + 1 CPUs to ensure we do not > - * remove the last CPU. > - */ > - for_each_node_by_type(dn, "cpu") { > - cpus_found++; > - > - if (cpus_found > cpus_to_remove) { > - of_node_put(dn); > - break; > - } > - > - /* Note that cpus_found is always 1 ahead of the index > - * into the cpu_drcs array, so we use cpus_found - 1 > - */ > - rc = of_property_read_u32(dn, "ibm,my-drc-index", > - &cpu_drcs[cpus_found - 1]); > - if (rc) { > - pr_warn("Error occurred getting drc-index for %pOFn\n", > - dn); > - of_node_put(dn); > - return -1; > - } > - } > - > - if (cpus_found < cpus_to_remove) { > - pr_warn("Failed to find enough CPUs (%d of %d) to remove\n", > - cpus_found, cpus_to_remove); > - } else if (cpus_found == cpus_to_remove) { > - pr_warn("Cannot remove all CPUs\n"); > - } > - > - return cpus_found; > -} > - > -static int dlpar_cpu_remove_by_count(u32 cpus_to_remove) > -{ > - u32 *cpu_drcs; > - int cpus_found; > - int cpus_removed = 0; > - int i, rc; > - > - pr_debug("Attempting to hot-remove %d CPUs\n", cpus_to_remove); > - > - cpu_drcs = kcalloc(cpus_to_remove, sizeof(*cpu_drcs), GFP_KERNEL); > - if (!cpu_drcs) > - return -EINVAL; > - > - cpus_found = find_dlpar_cpus_to_remove(cpu_drcs, cpus_to_remove); > - if (cpus_found <= cpus_to_remove) { > - kfree(cpu_drcs); > - return -EINVAL; > - } > - > - for (i = 0; i < cpus_to_remove; i++) { > - rc = dlpar_cpu_remove_by_index(cpu_drcs[i]); > - if (rc) > - break; > - > - cpus_removed++; > - } > - > - if (cpus_removed != cpus_to_remove) { > - pr_warn("CPU hot-remove failed, adding back removed CPUs\n"); > - > - for (i = 0; i < cpus_removed; i++) > - dlpar_cpu_add(cpu_drcs[i]); > - > - rc = -EINVAL; > - } else { > - rc = 0; > - } > - > - kfree(cpu_drcs); > - return rc; > -} > - > -static int find_drc_info_cpus_to_add(struct device_node *cpus, > - struct property *info, > - u32 *cpu_drcs, u32 cpus_to_add) > -{ > - struct of_drc_info drc; > - const __be32 *value; > - u32 count, drc_index; > - int cpus_found = 0; > - int i, j; > - > - if (!info) > - return -1; > - > - value = of_prop_next_u32(info, NULL, &count); > - if (value) > - value++; > - > - for (i = 0; i < count; i++) { > - of_read_drc_info_cell(&info, &value, &drc); > - if (strncmp(drc.drc_type, "CPU", 3)) > - break; > - > - drc_index = drc.drc_index_start; > - for (j = 0; j < drc.num_sequential_elems; j++) { > - if (dlpar_cpu_exists(cpus, drc_index)) > - continue; > - > - cpu_drcs[cpus_found++] = drc_index; > - > - if (cpus_found == cpus_to_add) > - return cpus_found; > - > - drc_index += drc.sequential_inc; > - } > - } > - > - return cpus_found; > -} > - > -static int find_drc_index_cpus_to_add(struct device_node *cpus, > - u32 *cpu_drcs, u32 cpus_to_add) > -{ > - int cpus_found = 0; > - int index, rc; > - u32 drc_index; > - > - /* Search the ibm,drc-indexes array for possible CPU drcs to > - * add. Note that the format of the ibm,drc-indexes array is > - * the number of entries in the array followed by the array > - * of drc values so we start looking at index = 1. > - */ > - index = 1; > - while (cpus_found < cpus_to_add) { > - rc = of_property_read_u32_index(cpus, "ibm,drc-indexes", > - index++, &drc_index); > - > - if (rc) > - break; > - > - if (dlpar_cpu_exists(cpus, drc_index)) > - continue; > - > - cpu_drcs[cpus_found++] = drc_index; > - } > - > - return cpus_found; > -} > - > -static int dlpar_cpu_add_by_count(u32 cpus_to_add) > -{ > - struct device_node *parent; > - struct property *info; > - u32 *cpu_drcs; > - int cpus_added = 0; > - int cpus_found; > - int i, rc; > - > - pr_debug("Attempting to hot-add %d CPUs\n", cpus_to_add); > - > - cpu_drcs = kcalloc(cpus_to_add, sizeof(*cpu_drcs), GFP_KERNEL); > - if (!cpu_drcs) > - return -EINVAL; > - > - parent = of_find_node_by_path("/cpus"); > - if (!parent) { > - pr_warn("Could not find CPU root node in device tree\n"); > - kfree(cpu_drcs); > - return -1; > - } > - > - info = of_find_property(parent, "ibm,drc-info", NULL); > - if (info) > - cpus_found = find_drc_info_cpus_to_add(parent, info, cpu_drcs, cpus_to_add); > - else > - cpus_found = find_drc_index_cpus_to_add(parent, cpu_drcs, cpus_to_add); > - > - of_node_put(parent); > - > - if (cpus_found < cpus_to_add) { > - pr_warn("Failed to find enough CPUs (%d of %d) to add\n", > - cpus_found, cpus_to_add); > - kfree(cpu_drcs); > - return -EINVAL; > - } > - > - for (i = 0; i < cpus_to_add; i++) { > - rc = dlpar_cpu_add(cpu_drcs[i]); > - if (rc) > - break; > - > - cpus_added++; > - } > - > - if (cpus_added < cpus_to_add) { > - pr_warn("CPU hot-add failed, removing any added CPUs\n"); > - > - for (i = 0; i < cpus_added; i++) > - dlpar_cpu_remove_by_index(cpu_drcs[i]); > - > - rc = -EINVAL; > - } else { > - rc = 0; > - } > - > - kfree(cpu_drcs); > - return rc; > -} > - > int dlpar_cpu(struct pseries_hp_errorlog *hp_elog) > { > u32 count, drc_index; > @@ -963,9 +753,7 @@ int dlpar_cpu(struct pseries_hp_errorlog *hp_elog) > > switch (hp_elog->action) { > case PSERIES_HP_ELOG_ACTION_REMOVE: > - if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT) > - rc = dlpar_cpu_remove_by_count(count); > - else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) { > + if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) { > rc = dlpar_cpu_remove_by_index(drc_index); > /* > * Setting the isolation state of an UNISOLATED/CONFIGURED > @@ -979,9 +767,7 @@ int dlpar_cpu(struct pseries_hp_errorlog *hp_elog) > rc = -EINVAL; > break; > case PSERIES_HP_ELOG_ACTION_ADD: > - if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT) > - rc = dlpar_cpu_add_by_count(count); > - else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) > + if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX) > rc = dlpar_cpu_add(drc_index); > else > rc = -EINVAL; > ^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code 2021-09-21 0:18 ` Daniel Henrique Barboza @ 2021-09-21 0:43 ` Nathan Lynch 0 siblings, 0 replies; 11+ messages in thread From: Nathan Lynch @ 2021-09-21 0:43 UTC (permalink / raw) To: Daniel Henrique Barboza, linuxppc-dev; +Cc: tyreld, ldufour, aneesh.kumar Daniel Henrique Barboza <danielhb413@gmail.com> writes: > On 9/20/21 10:55, Nathan Lynch wrote: >> The core DLPAR code supports two actions (add and remove) and three >> subtypes of action: >> >> * By DRC index: the action is attempted on a single specified resource. >> This is the usual case for processors. >> * By indexed count: the action is attempted on a range of resources >> beginning at the specified index. This is implemented only by the memory >> DLPAR code. >> * By count: the lower layer (CPU or memory) is responsible for locating the >> specified number of resources to which the action can be applied. >> >> I cannot find any evidence of the "by count" subtype being used by drmgr or >> qemu for processors. And when I try to exercise this code, the add case >> does not work: > > > Just to clarify: did you check both CPU and memory cases and found out that the > 'by count' subtype isn't used with CPUs, but drmgr has some cases in which > 'by count' is used with LMBs? Yes, drmgr uses both the 'by count' and the 'by index' methods for memory currently on PowerVM. > I'm asking because I worked with a part of the LMB removal code a few months ago, > and got stuck in a situation in which the 'by count' and 'by indexed count' are > similar enough to feel repetitive, but distinct enough to not be easily reduced > into a single function. If drmgr wasn't using the 'by count' subtypes for LMBs > that would be a good chance for more code redux. The 'by count' method is definitely used for memory on PowerVM. I was under the impression that the 'by indexed count' method was used by qemu for memory sometimes; I'm pretty sure it's not used on PowerVM. >> Summary: >> >> * This code has not worked reliably since its introduction. >> * There is no evidence that it is used. >> * It contains questionable rollback behaviors in error paths which are >> difficult to test. >> >> So let's remove it. >> >> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com> >> Fixes: ac71380071d1 ("powerpc/pseries: Add CPU dlpar remove functionality") >> Fixes: 90edf184b9b7 ("powerpc/pseries: Add CPU dlpar add functionality") >> Fixes: b015f6bc9547 ("powerpc/pseries: Add cpu DLPAR support for drc-info property") >> --- > > Tested with a QEMU pseries guest, no issues found. > > > Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> > Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com> Thanks! ^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2021-09-22 2:28 UTC | newest] Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-09-20 13:55 [PATCH 0/3] CPU DLPAR/hotplug for v5.16 Nathan Lynch 2021-09-20 13:55 ` [PATCH 1/3] powerpc/pseries/cpuhp: cache node corrections Nathan Lynch 2021-09-20 23:59 ` Daniel Henrique Barboza 2021-09-20 13:55 ` [PATCH 2/3] powerpc/cpuhp: BUG -> WARN conversion in offline path Nathan Lynch 2021-09-20 14:26 ` Christophe Leroy 2021-09-20 14:39 ` Nathan Lynch 2021-09-21 0:05 ` Daniel Henrique Barboza 2021-09-20 13:55 ` [PATCH 3/3] powerpc/pseries/cpuhp: delete add/remove_by_count code Nathan Lynch 2021-09-20 21:50 ` kernel test robot 2021-09-21 0:18 ` Daniel Henrique Barboza 2021-09-21 0:43 ` Nathan Lynch
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