6.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Russell Currey ruscur@russell.cc
[ Upstream commit eac030b22ea12cdfcbb2e941c21c03964403c63f ]
lppaca_shared_proc() takes a pointer to the lppaca which is typically accessed through get_lppaca(). With DEBUG_PREEMPT enabled, this leads to checking if preemption is enabled, for example:
BUG: using smp_processor_id() in preemptible [00000000] code: grep/10693 caller is lparcfg_data+0x408/0x19a0 CPU: 4 PID: 10693 Comm: grep Not tainted 6.5.0-rc3 #2 Call Trace: dump_stack_lvl+0x154/0x200 (unreliable) check_preemption_disabled+0x214/0x220 lparcfg_data+0x408/0x19a0 ...
This isn't actually a problem however, as it does not matter which lppaca is accessed, the shared proc state will be the same. vcpudispatch_stats_procfs_init() already works around this by disabling preemption, but the lparcfg code does not, erroring any time /proc/powerpc/lparcfg is accessed with DEBUG_PREEMPT enabled.
Instead of disabling preemption on the caller side, rework lppaca_shared_proc() to not take a pointer and instead directly access the lppaca, bypassing any potential preemption checks.
Fixes: f13c13a00512 ("powerpc: Stop using non-architected shared_proc field in lppaca") Signed-off-by: Russell Currey ruscur@russell.cc [mpe: Rework to avoid needing a definition in paca.h and lppaca.h] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://msgid.link/20230823055317.751786-4-mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/include/asm/lppaca.h | 11 +++++++++-- arch/powerpc/platforms/pseries/lpar.c | 10 +--------- arch/powerpc/platforms/pseries/lparcfg.c | 4 ++-- arch/powerpc/platforms/pseries/setup.c | 2 +- drivers/cpuidle/cpuidle-pseries.c | 8 +------- 5 files changed, 14 insertions(+), 21 deletions(-)
diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h index fe278172e9d42..ee1488d38fdc1 100644 --- a/arch/powerpc/include/asm/lppaca.h +++ b/arch/powerpc/include/asm/lppaca.h @@ -45,6 +45,7 @@ #include <asm/types.h> #include <asm/mmu.h> #include <asm/firmware.h> +#include <asm/paca.h>
/* * The lppaca is the "virtual processor area" registered with the hypervisor, @@ -127,14 +128,20 @@ struct lppaca { */ #define LPPACA_OLD_SHARED_PROC 2
-static inline bool lppaca_shared_proc(struct lppaca *l) +#ifdef CONFIG_PPC_PSERIES +/* + * All CPUs should have the same shared proc value, so directly access the PACA + * to avoid false positives from DEBUG_PREEMPT. + */ +static inline bool lppaca_shared_proc(void) { + struct lppaca *l = local_paca->lppaca_ptr; + if (!firmware_has_feature(FW_FEATURE_SPLPAR)) return false; return !!(l->__old_status & LPPACA_OLD_SHARED_PROC); }
-#ifdef CONFIG_PPC_PSERIES #define get_lppaca() (get_paca()->lppaca_ptr) #endif
diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 2eab323f69706..cb2f1211f7ebf 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -639,16 +639,8 @@ static const struct proc_ops vcpudispatch_stats_freq_proc_ops = {
static int __init vcpudispatch_stats_procfs_init(void) { - /* - * Avoid smp_processor_id while preemptible. All CPUs should have - * the same value for lppaca_shared_proc. - */ - preempt_disable(); - if (!lppaca_shared_proc(get_lppaca())) { - preempt_enable(); + if (!lppaca_shared_proc()) return 0; - } - preempt_enable();
if (!proc_create("powerpc/vcpudispatch_stats", 0600, NULL, &vcpudispatch_stats_proc_ops)) diff --git a/arch/powerpc/platforms/pseries/lparcfg.c b/arch/powerpc/platforms/pseries/lparcfg.c index 8acc705095209..1c151d77e74b3 100644 --- a/arch/powerpc/platforms/pseries/lparcfg.c +++ b/arch/powerpc/platforms/pseries/lparcfg.c @@ -206,7 +206,7 @@ static void parse_ppp_data(struct seq_file *m) ppp_data.active_system_procs);
/* pool related entries are appropriate for shared configs */ - if (lppaca_shared_proc(get_lppaca())) { + if (lppaca_shared_proc()) { unsigned long pool_idle_time, pool_procs;
seq_printf(m, "pool=%d\n", ppp_data.pool_num); @@ -560,7 +560,7 @@ static int pseries_lparcfg_data(struct seq_file *m, void *v) partition_potential_processors);
seq_printf(m, "shared_processor_mode=%d\n", - lppaca_shared_proc(get_lppaca())); + lppaca_shared_proc());
#ifdef CONFIG_PPC_64S_HASH_MMU if (!radix_enabled()) diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index e2a57cfa6c837..0ef2a7e014aa1 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -847,7 +847,7 @@ static void __init pSeries_setup_arch(void) if (firmware_has_feature(FW_FEATURE_LPAR)) { vpa_init(boot_cpuid);
- if (lppaca_shared_proc(get_lppaca())) { + if (lppaca_shared_proc()) { static_branch_enable(&shared_processor); pv_spinlocks_init(); #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING diff --git a/drivers/cpuidle/cpuidle-pseries.c b/drivers/cpuidle/cpuidle-pseries.c index a7d33f3ee01e7..14db9b7d985d1 100644 --- a/drivers/cpuidle/cpuidle-pseries.c +++ b/drivers/cpuidle/cpuidle-pseries.c @@ -414,13 +414,7 @@ static int __init pseries_idle_probe(void) return -ENODEV;
if (firmware_has_feature(FW_FEATURE_SPLPAR)) { - /* - * Use local_paca instead of get_lppaca() since - * preemption is not disabled, and it is not required in - * fact, since lppaca_ptr does not need to be the value - * associated to the current CPU, it can be from any CPU. - */ - if (lppaca_shared_proc(local_paca->lppaca_ptr)) { + if (lppaca_shared_proc()) { cpuidle_state_table = shared_states; max_idle_state = ARRAY_SIZE(shared_states); } else {