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| author |  Russell Currey <ruscur@russell.cc>
| 2023-08-23 15:53:17 +1000 |
|---|---|---|
| committer |  Michael Ellerman <mpe@ellerman.id.au>
| 2023-08-24 22:33:17 +1000 |
| commit | eac030b22ea12cdfcbb2e941c21c03964403c63f (patch) | |
| tree | 6e20ff95a5a5b8588b87160065d9a0d5b836a5a2 /arch/powerpc/include | |
| parent | powerpc: Don't include lppaca.h in paca.h (diff) | |
| download | linux-eac030b22ea12cdfcbb2e941c21c03964403c63f.tar.gz linux-eac030b22ea12cdfcbb2e941c21c03964403c63f.tar.bz2 linux-eac030b22ea12cdfcbb2e941c21c03964403c63f.zip | |
powerpc/pseries: Rework lppaca_shared_proc() to avoid DEBUG_PREEMPT
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
Diffstat (limited to 'arch/powerpc/include')
| -rw-r--r-- | arch/powerpc/include/asm/lppaca.h | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h index b6a63fa0965f..61ec2447dabf 100644 --- a/arch/powerpc/include/asm/lppaca.h +++ b/arch/powerpc/include/asm/lppaca.h @@ -23,6 +23,7 @@ #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, @@ -105,14 +106,20 @@ 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 |