diff options
| -rw-r--r-- | Documentation/powerpc/transactional_memory.txt | 32 | ||||
| -rw-r--r-- | arch/powerpc/include/asm/cputable.h | 10 | ||||
| -rw-r--r-- | arch/powerpc/include/uapi/asm/cputable.h | 1 | ||||
| -rw-r--r-- | arch/powerpc/include/uapi/asm/tm.h | 2 | ||||
| -rw-r--r-- | arch/powerpc/kernel/cputable.c | 4 | ||||
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 35 | ||||
| -rw-r--r-- | tools/testing/selftests/powerpc/tm/Makefile | 4 | ||||
| -rw-r--r-- | tools/testing/selftests/powerpc/tm/tm-syscall.c | 3 |
8 files changed, 66 insertions, 25 deletions
diff --git a/Documentation/powerpc/transactional_memory.txt b/Documentation/powerpc/transactional_memory.txt index ded6979..ba0a2a4 100644 --- a/Documentation/powerpc/transactional_memory.txt +++ b/Documentation/powerpc/transactional_memory.txt @@ -74,22 +74,23 @@ Causes of transaction aborts Syscalls ======== -Performing syscalls from within transaction is not recommended, and can lead -to unpredictable results. +Syscalls made from within an active transaction will not be performed and the +transaction will be doomed by the kernel with the failure code TM_CAUSE_SYSCALL +| TM_CAUSE_PERSISTENT. -Syscalls do not by design abort transactions, but beware: The kernel code will -not be running in transactional state. The effect of syscalls will always -remain visible, but depending on the call they may abort your transaction as a -side-effect, read soon-to-be-aborted transactional data that should not remain -invisible, etc. If you constantly retry a transaction that constantly aborts -itself by calling a syscall, you'll have a livelock & make no progress. +Syscalls made from within a suspended transaction are performed as normal and +the transaction is not explicitly doomed by the kernel. However, what the +kernel does to perform the syscall may result in the transaction being doomed +by the hardware. The syscall is performed in suspended mode so any side +effects will be persistent, independent of transaction success or failure. No +guarantees are provided by the kernel about which syscalls will affect +transaction success. -Simple syscalls (e.g. sigprocmask()) "could" be OK. Even things like write() -from, say, printf() should be OK as long as the kernel does not access any -memory that was accessed transactionally. - -Consider any syscalls that happen to work as debug-only -- not recommended for -production use. Best to queue them up till after the transaction is over. +Care must be taken when relying on syscalls to abort during active transactions +if the calls are made via a library. Libraries may cache values (which may +give the appearance of success) or perform operations that cause transaction +failure before entering the kernel (which may produce different failure codes). +Examples are glibc's getpid() and lazy symbol resolution. Signals @@ -176,8 +177,7 @@ kernel aborted a transaction: TM_CAUSE_RESCHED Thread was rescheduled. TM_CAUSE_TLBI Software TLB invalid. TM_CAUSE_FAC_UNAV FP/VEC/VSX unavailable trap. - TM_CAUSE_SYSCALL Currently unused; future syscalls that must abort - transactions for consistency will use this. + TM_CAUSE_SYSCALL Syscall from active transaction. TM_CAUSE_SIGNAL Signal delivered. TM_CAUSE_MISC Currently unused. TM_CAUSE_ALIGNMENT Alignment fault. diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h index 6367b83..4994648 100644 --- a/arch/powerpc/include/asm/cputable.h +++ b/arch/powerpc/include/asm/cputable.h @@ -242,11 +242,13 @@ enum { /* We only set the TM feature if the kernel was compiled with TM supprt */ #ifdef CONFIG_PPC_TRANSACTIONAL_MEM -#define CPU_FTR_TM_COMP CPU_FTR_TM -#define PPC_FEATURE2_HTM_COMP PPC_FEATURE2_HTM +#define CPU_FTR_TM_COMP CPU_FTR_TM +#define PPC_FEATURE2_HTM_COMP PPC_FEATURE2_HTM +#define PPC_FEATURE2_HTM_NOSC_COMP PPC_FEATURE2_HTM_NOSC #else -#define CPU_FTR_TM_COMP 0 -#define PPC_FEATURE2_HTM_COMP 0 +#define CPU_FTR_TM_COMP 0 +#define PPC_FEATURE2_HTM_COMP 0 +#define PPC_FEATURE2_HTM_NOSC_COMP 0 #endif /* We need to mark all pages as being coherent if we're SMP or we have a diff --git a/arch/powerpc/include/uapi/asm/cputable.h b/arch/powerpc/include/uapi/asm/cputable.h index de2c0e4..4368604 100644 --- a/arch/powerpc/include/uapi/asm/cputable.h +++ b/arch/powerpc/include/uapi/asm/cputable.h @@ -42,5 +42,6 @@ #define PPC_FEATURE2_ISEL 0x08000000 #define PPC_FEATURE2_TAR 0x04000000 #define PPC_FEATURE2_VEC_CRYPTO 0x02000000 +#define PPC_FEATURE2_HTM_NOSC 0x01000000 #endif /* _UAPI__ASM_POWERPC_CPUTABLE_H */ diff --git a/arch/powerpc/include/uapi/asm/tm.h b/arch/powerpc/include/uapi/asm/tm.h index 5d836b7..5047659 100644 --- a/arch/powerpc/include/uapi/asm/tm.h +++ b/arch/powerpc/include/uapi/asm/tm.h @@ -11,7 +11,7 @@ #define TM_CAUSE_RESCHED 0xde #define TM_CAUSE_TLBI 0xdc #define TM_CAUSE_FAC_UNAV 0xda -#define TM_CAUSE_SYSCALL 0xd8 /* future use */ +#define TM_CAUSE_SYSCALL 0xd8 #define TM_CAUSE_MISC 0xd6 /* future use */ #define TM_CAUSE_SIGNAL 0xd4 #define TM_CAUSE_ALIGNMENT 0xd2 diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c index 60262fd..7d80bfd 100644 --- a/arch/powerpc/kernel/cputable.c +++ b/arch/powerpc/kernel/cputable.c @@ -108,7 +108,9 @@ extern void __restore_cpu_e6500(void); PPC_FEATURE_TRUE_LE | \ PPC_FEATURE_PSERIES_PERFMON_COMPAT) #define COMMON_USER2_POWER8 (PPC_FEATURE2_ARCH_2_07 | \ - PPC_FEATURE2_HTM_COMP | PPC_FEATURE2_DSCR | \ + PPC_FEATURE2_HTM_COMP | \ + PPC_FEATURE2_HTM_NOSC_COMP | \ + PPC_FEATURE2_DSCR | \ PPC_FEATURE2_ISEL | PPC_FEATURE2_TAR | \ PPC_FEATURE2_VEC_CRYPTO) #define COMMON_USER_PA6T (COMMON_USER_PPC64 | PPC_FEATURE_PA6T |\ diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 278888e..579e0f9 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -34,6 +34,7 @@ #include <asm/ftrace.h> #include <asm/hw_irq.h> #include <asm/context_tracking.h> +#include <asm/tm.h> /* * System calls. @@ -51,6 +52,12 @@ exception_marker: .globl system_call_common system_call_common: +#ifdef CONFIG_PPC_TRANSACTIONAL_MEM +BEGIN_FTR_SECTION + extrdi. r10, r12, 1, (63-MSR_TS_T_LG) /* transaction active? */ + bne tabort_syscall +END_FTR_SECTION_IFSET(CPU_FTR_TM) +#endif andi. r10,r12,MSR_PR mr r10,r1 addi r1,r1,-INT_FRAME_SIZE @@ -311,6 +318,34 @@ syscall_exit_work: bl do_syscall_trace_leave b ret_from_except +#ifdef CONFIG_PPC_TRANSACTIONAL_MEM +tabort_syscall: + /* Firstly we need to enable TM in the kernel */ + mfmsr r10 + li r13, 1 + rldimi r10, r13, MSR_TM_LG, 63-MSR_TM_LG + mtmsrd r10, 0 + + /* tabort, this dooms the transaction, nothing else */ + li r13, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT) + TABORT(R13) + + /* + * Return directly to userspace. We have corrupted user register state, + * but userspace will never see that register state. Execution will + * resume after the tbegin of the aborted transaction with the + * checkpointed register state. + */ + li r13, MSR_RI + andc r10, r10, r13 + mtmsrd r10, 1 + mtspr SPRN_SRR0, r11 + mtspr SPRN_SRR1, r12 + + rfid + b . /* prevent speculative execution */ +#endif + /* Save non-volatile GPRs, if not already saved. */ _GLOBAL(save_nvgprs) ld r11,_TRAP(r1) diff --git a/tools/testing/selftests/powerpc/tm/Makefile b/tools/testing/selftests/powerpc/tm/Makefile index 6bff955..4bea62a 100644 --- a/tools/testing/selftests/powerpc/tm/Makefile +++ b/tools/testing/selftests/powerpc/tm/Makefile @@ -1,11 +1,11 @@ -TEST_PROGS := tm-resched-dscr +TEST_PROGS := tm-resched-dscr tm-syscall all: $(TEST_PROGS) $(TEST_PROGS): ../harness.c tm-syscall: tm-syscall-asm.S -tm-syscall: CFLAGS += -mhtm +tm-syscall: CFLAGS += -mhtm -I../../../../../usr/include include ../../lib.mk diff --git a/tools/testing/selftests/powerpc/tm/tm-syscall.c b/tools/testing/selftests/powerpc/tm/tm-syscall.c index 3ed8d4b..1276e23 100644 --- a/tools/testing/selftests/powerpc/tm/tm-syscall.c +++ b/tools/testing/selftests/powerpc/tm/tm-syscall.c @@ -82,7 +82,8 @@ int tm_syscall(void) unsigned count = 0; struct timeval end, now; - SKIP_IF(!((long)get_auxv_entry(AT_HWCAP2) & PPC_FEATURE2_HTM)); + SKIP_IF(!((long)get_auxv_entry(AT_HWCAP2) + & PPC_FEATURE2_HTM_NOSC)); setbuf(stdout, NULL); printf("Testing transactional syscalls for %d seconds...\n", TEST_DURATION); |
