From 640e922501103aaf2e0abb4cf4de5d49fa8342f7 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Tue, 10 Dec 2013 23:07:45 +0000 Subject: powerpc: fix exception clearing in e500 SPE float emulation The e500 SPE floating-point emulation code clears existing exceptions (__FPU_FPSCR &= ~FP_EX_MASK;) before ORing in the exceptions from the emulated operation. However, these exception bits are the "sticky", cumulative exception bits, and should only be cleared by the user program setting SPEFSCR, not implicitly by any floating-point instruction (whether executed purely by the hardware or emulated). The spurious clearing of these bits shows up as missing exceptions in glibc testing. Fixing this, however, is not as simple as just not clearing the bits, because while the bits may be from previous floating-point operations (in which case they should not be cleared), the processor can also set the sticky bits itself before the interrupt for an exception occurs, and this can happen in cases when IEEE 754 semantics are that the sticky bit should not be set. Specifically, the "invalid" sticky bit is set in various cases with non-finite operands, where IEEE 754 semantics do not involve raising such an exception, and the "underflow" sticky bit is set in cases of exact underflow, whereas IEEE 754 semantics are that this flag is set only for inexact underflow. Thus, for correct emulation the kernel needs to know the setting of these two sticky bits before the instruction being emulated. When a floating-point operation raises an exception, the kernel can note the state of the sticky bits immediately afterwards. Some functions that affect the state of these bits, such as fesetenv and feholdexcept, need to use prctl with PR_GET_FPEXC and PR_SET_FPEXC anyway, and so it is natural to record the state of those bits during that call into the kernel and so avoid any need for a separate call into the kernel to inform it of a change to those bits. Thus, the interface I chose to use (in this patch and the glibc port) is that one of those prctl calls must be made after any userspace change to those sticky bits, other than through a floating-point operation that traps into the kernel anyway. feclearexcept and fesetexceptflag duly make those calls, which would not be required were it not for this issue. The previous EGLIBC port, and the uClibc code copied from it, is fundamentally broken as regards any use of prctl for floating-point exceptions because it didn't use the PR_FP_EXC_SW_ENABLE bit in its prctl calls (and did various worse things, such as passing a pointer when prctl expected an integer). If you avoid anything where prctl is used, the clearing of sticky bits still means it will never give anything approximating correct exception semantics with existing kernels. I don't believe the patch makes things any worse for existing code that doesn't try to inform the kernel of changes to sticky bits - such code may get incorrect exceptions in some cases, but it would have done so anyway in other cases. Signed-off-by: Joseph Myers Signed-off-by: Scott Wood --- arch/powerpc/include/asm/processor.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/include/asm/processor.h') diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index fc14a38c7ccf..91441d9cbaae 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -256,6 +256,8 @@ struct thread_struct { unsigned long evr[32]; /* upper 32-bits of SPE regs */ u64 acc; /* Accumulator */ unsigned long spefscr; /* SPE & eFP status */ + unsigned long spefscr_last; /* SPEFSCR value on last prctl + call or trap return */ int used_spe; /* set if process has used spe */ #endif /* CONFIG_SPE */ #ifdef CONFIG_PPC_TRANSACTIONAL_MEM @@ -317,7 +319,9 @@ struct thread_struct { (_ALIGN_UP(sizeof(init_thread_info), 16) + (unsigned long) &init_stack) #ifdef CONFIG_SPE -#define SPEFSCR_INIT .spefscr = SPEFSCR_FINVE | SPEFSCR_FDBZE | SPEFSCR_FUNFE | SPEFSCR_FOVFE, +#define SPEFSCR_INIT \ + .spefscr = SPEFSCR_FINVE | SPEFSCR_FDBZE | SPEFSCR_FUNFE | SPEFSCR_FOVFE, \ + .spefscr_last = SPEFSCR_FINVE | SPEFSCR_FDBZE | SPEFSCR_FUNFE | SPEFSCR_FOVFE, #else #define SPEFSCR_INIT #endif -- cgit v1.2.3 From d31626f70b6103f4d9153b75d07e0e8795728cc9 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Mon, 13 Jan 2014 15:56:29 +1100 Subject: powerpc: Don't corrupt transactional state when using FP/VMX in kernel Currently, when we have a process using the transactional memory facilities on POWER8 (that is, the processor is in transactional or suspended state), and the process enters the kernel and the kernel then uses the floating-point or vector (VMX/Altivec) facility, we end up corrupting the user-visible FP/VMX/VSX state. This happens, for example, if a page fault causes a copy-on-write operation, because the copy_page function will use VMX to do the copy on POWER8. The test program below demonstrates the bug. The bug happens because when FP/VMX state for a transactional process is stored in the thread_struct, we store the checkpointed state in .fp_state/.vr_state and the transactional (current) state in .transact_fp/.transact_vr. However, when the kernel wants to use FP/VMX, it calls enable_kernel_fp() or enable_kernel_altivec(), which saves the current state in .fp_state/.vr_state. Furthermore, when we return to the user process we return with FP/VMX/VSX disabled. The next time the process uses FP/VMX/VSX, we don't know which set of state (the current register values, .fp_state/.vr_state, or .transact_fp/.transact_vr) we should be using, since we have no way to tell if we are still in the same transaction, and if not, whether the previous transaction succeeded or failed. Thus it is necessary to strictly adhere to the rule that if FP has been enabled at any point in a transaction, we must keep FP enabled for the user process with the current transactional state in the FP registers, until we detect that it is no longer in a transaction. Similarly for VMX; once enabled it must stay enabled until the process is no longer transactional. In order to keep this rule, we add a new thread_info flag which we test when returning from the kernel to userspace, called TIF_RESTORE_TM. This flag indicates that there is FP/VMX/VSX state to be restored before entering userspace, and when it is set the .tm_orig_msr field in the thread_struct indicates what state needs to be restored. The restoration is done by restore_tm_state(). The TIF_RESTORE_TM bit is set by new giveup_fpu/altivec_maybe_transactional helpers, which are called from enable_kernel_fp/altivec, giveup_vsx, and flush_fp/altivec_to_thread instead of giveup_fpu/altivec. The other thing to be done is to get the transactional FP/VMX/VSX state from .fp_state/.vr_state when doing reclaim, if that state has been saved there by giveup_fpu/altivec_maybe_transactional. Having done this, we set the FP/VMX bit in the thread's MSR after reclaim to indicate that that part of the state is now valid (having been reclaimed from the processor's checkpointed state). Finally, in the signal handling code, we move the clearing of the transactional state bits in the thread's MSR a bit earlier, before calling flush_fp_to_thread(), so that we don't unnecessarily set the TIF_RESTORE_TM bit. This is the test program: /* Michael Neuling 4/12/2013 * * See if the altivec state is leaked out of an aborted transaction due to * kernel vmx copy loops. * * gcc -m64 htm_vmxcopy.c -o htm_vmxcopy * */ /* We don't use all of these, but for reference: */ int main(int argc, char *argv[]) { long double vecin = 1.3; long double vecout; unsigned long pgsize = getpagesize(); int i; int fd; int size = pgsize*16; char tmpfile[] = "/tmp/page_faultXXXXXX"; char buf[pgsize]; char *a; uint64_t aborted = 0; fd = mkstemp(tmpfile); assert(fd >= 0); memset(buf, 0, pgsize); for (i = 0; i < size; i += pgsize) assert(write(fd, buf, pgsize) == pgsize); unlink(tmpfile); a = mmap(NULL, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0); assert(a != MAP_FAILED); asm __volatile__( "lxvd2x 40,0,%[vecinptr] ; " // set 40 to initial value TBEGIN "beq 3f ;" TSUSPEND "xxlxor 40,40,40 ; " // set 40 to 0 "std 5, 0(%[map]) ;" // cause kernel vmx copy page TABORT TRESUME TEND "li %[res], 0 ;" "b 5f ;" "3: ;" // Abort handler "li %[res], 1 ;" "5: ;" "stxvd2x 40,0,%[vecoutptr] ; " : [res]"=r"(aborted) : [vecinptr]"r"(&vecin), [vecoutptr]"r"(&vecout), [map]"r"(a) : "memory", "r0", "r3", "r4", "r5", "r6", "r7"); if (aborted && (vecin != vecout)){ printf("FAILED: vector state leaked on abort %f != %f\n", (double)vecin, (double)vecout); exit(1); } munmap(a, size); close(fd); printf("PASSED!\n"); return 0; } Signed-off-by: Paul Mackerras Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/include/asm/processor.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/powerpc/include/asm/processor.h') diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index fc14a38c7ccf..232a2fa5b483 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -373,6 +373,8 @@ extern int set_endian(struct task_struct *tsk, unsigned int val); extern int get_unalign_ctl(struct task_struct *tsk, unsigned long adr); extern int set_unalign_ctl(struct task_struct *tsk, unsigned int val); +extern void fp_enable(void); +extern void vec_enable(void); extern void load_fp_state(struct thread_fp_state *fp); extern void store_fp_state(struct thread_fp_state *fp); extern void load_vr_state(struct thread_vr_state *vr); -- cgit v1.2.3 From 962e7bd4976516c34fc9ef51d536aab801980767 Mon Sep 17 00:00:00 2001 From: Deepthi Dharwar Date: Tue, 14 Jan 2014 16:26:02 +0530 Subject: powerpc/pseries/cpuidle: Move processor_idle.c to drivers/cpuidle. Move the file from arch specific pseries/processor_idle.c to drivers/cpuidle/cpuidle-pseries.c Make the relevant Makefile and Kconfig changes. Also, introduce Kconfig.powerpc in drivers/cpuidle for all powerpc cpuidle drivers. Signed-off-by: Deepthi Dharwar Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/include/asm/processor.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/powerpc/include/asm/processor.h') diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index 8ca20ac28dc2..c2c0f4478be3 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -451,7 +451,7 @@ enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF}; extern int powersave_nap; /* set if nap mode can be used in idle loop */ extern void power7_nap(void); -#ifdef CONFIG_PSERIES_IDLE +#ifdef CONFIG_PSERIES_CPUIDLE extern void update_smt_snooze_delay(int cpu, int residency); #else static inline void update_smt_snooze_delay(int cpu, int residency) {} -- cgit v1.2.3 From 3fa8cad82b94d0bed002571bd246f2299ffc876b Mon Sep 17 00:00:00 2001 From: Deepthi Dharwar Date: Tue, 14 Jan 2014 16:26:38 +0530 Subject: powerpc/pseries/cpuidle: smt-snooze-delay cleanup. smt-snooze-delay was designed to disable NAP state or delay the entry to the NAP state prior to adoption of cpuidle framework. This is per-cpu variable. With the coming of CPUIDLE framework, states can be disabled on per-cpu basis using the cpuidle/enable sysfs entry. Also, with the coming of cpuidle driver each state's target residency is per-driver unlike earlier which was per-device. Therefore, the per-cpu sysfs smt-snooze-delay which decides the target residency of the idle state on a particular cpu causes more confusion to the user as we cannot have different smt-snooze-delay (target residency) values for each cpu. In the current code, smt-snooze-delay functionality is completely broken. It makes sense to remove smt-snooze-delay from idle driver with the coming of cpuidle framework. However, sysfs files are retained as ppc64_util currently utilises it. Once we fix ppc64_util, propose to clean up the kernel code. Signed-off-by: Deepthi Dharwar Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/include/asm/processor.h | 7 ------- 1 file changed, 7 deletions(-) (limited to 'arch/powerpc/include/asm/processor.h') diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index c2c0f4478be3..b62de43ae5f3 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -450,13 +450,6 @@ enum idle_boot_override {IDLE_NO_OVERRIDE = 0, IDLE_POWERSAVE_OFF}; extern int powersave_nap; /* set if nap mode can be used in idle loop */ extern void power7_nap(void); - -#ifdef CONFIG_PSERIES_CPUIDLE -extern void update_smt_snooze_delay(int cpu, int residency); -#else -static inline void update_smt_snooze_delay(int cpu, int residency) {} -#endif - extern void flush_instruction_cache(void); extern void hard_reset_now(void); extern void poweroff_now(void); -- cgit v1.2.3