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Violators will be prosecuted for from ; Tue, 20 Feb 2018 00:23:02 -0000 From: Cyril Bur To: mikey@neuling.org, benh@kernel.crashing.org, linuxppc-dev@lists.ozlabs.org Subject: [RFC PATCH 10/12] [WIP] powerpc/tm: Correctly save/restore checkpointed sprs Date: Tue, 20 Feb 2018 11:22:39 +1100 In-Reply-To: <20180220002241.29648-1-cyrilbur@gmail.com> References: <20180220002241.29648-1-cyrilbur@gmail.com> Message-Id: <20180220002241.29648-11-cyrilbur@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --- arch/powerpc/kernel/process.c | 57 +++++++++++++++++++++++++++++++++++++++++-- arch/powerpc/kernel/ptrace.c | 9 +++---- 2 files changed, 58 insertions(+), 8 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index cd3ae80a6878..674f75c56172 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -859,6 +859,8 @@ static inline bool tm_enabled(struct task_struct *tsk) return tsk && tsk->thread.regs && (tsk->thread.regs->msr & MSR_TM); } +static inline void save_sprs(struct thread_struct *t); + static void tm_reclaim_thread(struct thread_struct *thr, uint8_t cause) { /* @@ -879,6 +881,8 @@ static void tm_reclaim_thread(struct thread_struct *thr, uint8_t cause) if (!MSR_TM_SUSPENDED(mfmsr())) return; + save_sprs(thr); + giveup_all(container_of(thr, struct task_struct, thread)); tm_reclaim(thr, cause); @@ -991,6 +995,37 @@ void tm_recheckpoint(struct thread_struct *thread) __tm_recheckpoint(thread); + /* + * This is a stripped down restore_sprs(), we need to do this + * now as we might go straight out to userspace and currently + * the checkpointed values are on the CPU. + * + * TODO: Improve + */ +#ifdef CONFIG_ALTIVEC + if (cpu_has_feature(CPU_FTR_ALTIVEC)) + mtspr(SPRN_VRSAVE, thread->vrsave); +#endif +#ifdef CONFIG_PPC_BOOK3S_64 + if (cpu_has_feature(CPU_FTR_DSCR)) { + u64 dscr = get_paca()->dscr_default; + if (thread->dscr_inherit) + dscr = thread->dscr; + + mtspr(SPRN_DSCR, dscr); + } + + if (cpu_has_feature(CPU_FTR_ARCH_207S)) { + /* The EBB regs aren't checkpointed */ + mtspr(SPRN_FSCR, thread->fscr); + + mtspr(SPRN_TAR, thread->tar); + } + + /* I think we don't need to */ + if (cpu_has_feature(CPU_FTR_ARCH_300)) + mtspr(SPRN_TIDR, thread->tidr); +#endif local_irq_restore(flags); } @@ -1193,6 +1228,11 @@ struct task_struct *__switch_to(struct task_struct *prev, #endif new_thread = &new->thread; + /* + * Why not &prev->thread; ? + * What is the difference between &prev->thread and + * ¤t->thread ? + */ old_thread = ¤t->thread; WARN_ON(!irqs_disabled()); @@ -1237,8 +1277,16 @@ struct task_struct *__switch_to(struct task_struct *prev, /* * We need to save SPRs before treclaim/trecheckpoint as these will * change a number of them. + * + * Because we're now reclaiming on kernel entry, we've had to + * already save them. Don't do it again. + * Note: To deliver a signal in the signal context, we'll have + * turned off TM because we don't want the signal context to + * have the transactional state of the main thread - what if + * we go through switch to at that point? Can we? */ - save_sprs(&prev->thread); + if (!prev->thread.regs || !MSR_TM_ACTIVE(prev->thread.regs->msr)) + save_sprs(&prev->thread); /* Save FPU, Altivec, VSX and SPE state */ giveup_all(prev); @@ -1260,8 +1308,13 @@ struct task_struct *__switch_to(struct task_struct *prev, * for this is we manually create a stack frame for new tasks that * directly returns through ret_from_fork() or * ret_from_kernel_thread(). See copy_thread() for details. + * + * It isn't stricly nessesary that we avoid the restore here + * because we'll simply restore again after the recheckpoint, + * but we can avoid it for performance reasons. */ - restore_sprs(old_thread, new_thread); + if (!new_thread->regs || !MSR_TM_ACTIVE(new_thread->regs->msr)) + restore_sprs(old_thread, new_thread); last = _switch(old_thread, new_thread); diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c index ca72d7391d40..16001987ba71 100644 --- a/arch/powerpc/kernel/ptrace.c +++ b/arch/powerpc/kernel/ptrace.c @@ -135,12 +135,9 @@ static void flush_tmregs_to_thread(struct task_struct *tsk) if ((!cpu_has_feature(CPU_FTR_TM)) || (tsk != current)) return; - if (MSR_TM_SUSPENDED(mfmsr())) { - tm_reclaim_current(TM_CAUSE_SIGNAL); - } else { - tm_enable(); - tm_save_sprs(&(tsk->thread)); - } + BUG_ON(MSR_TM_SUSPENDED(mfmsr())); + tm_enable(); + tm_save_sprs(&(tsk->thread)); } #else static inline void flush_tmregs_to_thread(struct task_struct *tsk) { } -- 2.16.2