From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753332AbdJGC2y (ORCPT ); Fri, 6 Oct 2017 22:28:54 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:41083 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752758AbdJGC2w (ORCPT ); Fri, 6 Oct 2017 22:28:52 -0400 From: Sukadev Bhattiprolu To: Michael Ellerman Cc: Benjamin Herrenschmidt , mikey@neuling.org, hbabu@us.ibm.com, nicholas.piggin@gmail.com, linuxppc-dev@ozlabs.org, Subject: [PATCH v2 13/18] powerpc: Add support for setting SPRN_TIDR Date: Fri, 6 Oct 2017 19:28:13 -0700 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1507343298-27496-1-git-send-email-sukadev@linux.vnet.ibm.com> References: <1507343298-27496-1-git-send-email-sukadev@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17100702-0024-0000-0000-0000174D5C4A X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007853; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000235; SDB=6.00927531; UDB=6.00466726; IPR=6.00707787; BA=6.00005623; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017430; XFM=3.00000015; UTC=2017-10-07 02:28:48 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17100702-0025-0000-0000-00004D0145BA Message-Id: <1507343298-27496-14-git-send-email-sukadev@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-10-07_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=2 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1710070033 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We need the SPRN_TIDR to be set for use with fast thread-wakeup (core- to-core wakeup) and also with CAPI. Each thread in a process needs to have a unique id within the process. But as explained below, for now, we assign globally unique thread ids to all threads in the system. Signed-off-by: Sukadev Bhattiprolu Signed-off-by: Philippe Bergheaud Signed-off-by: Christophe Lombard --- Changelog[v3] - Merge changes with and address comments to Christophe's patch. (i.e drop CONFIG_PPC_VAS; use CONFIG_PPC64; check CPU_ARCH_300 before setting TIDR). Defer following to separate patches: - emulation parts of Christophe's patch, - setting TIDR for tasks other than 'current' - setting feature bit in AT_HWCAP2 Changelog[v2] - Michael Ellerman: Use an interface to assign TIDR so it is assigned to only threads that need it; move assignment to restore_sprs(). Drop lint from rebase; --- arch/powerpc/include/asm/processor.h | 1 + arch/powerpc/include/asm/switch_to.h | 3 + arch/powerpc/kernel/process.c | 122 +++++++++++++++++++++++++++++++++++ 3 files changed, 126 insertions(+) diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index fab7ff8..58cc212 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -329,6 +329,7 @@ struct thread_struct { */ int dscr_inherit; unsigned long ppr; /* used to save/restore SMT priority */ + unsigned long tidr; #endif #ifdef CONFIG_PPC_BOOK3S_64 unsigned long tar; diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h index 17c8380..f5da32f 100644 --- a/arch/powerpc/include/asm/switch_to.h +++ b/arch/powerpc/include/asm/switch_to.h @@ -91,4 +91,7 @@ static inline void clear_task_ebb(struct task_struct *t) #endif } +extern int set_thread_tidr(struct task_struct *t); +extern void clear_thread_tidr(struct task_struct *t); + #endif /* _ASM_POWERPC_SWITCH_TO_H */ diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 37ed60b..d861fcd 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1120,6 +1120,13 @@ static inline void restore_sprs(struct thread_struct *old_thread, mtspr(SPRN_TAR, new_thread->tar); } #endif +#ifdef CONFIG_PPC64 + if (old_thread->tidr != new_thread->tidr) { + /* TIDR should be non-zero only with ISA3.0. */ + WARN_ON_ONCE(!cpu_has_feature(CPU_FTR_ARCH_300)); + mtspr(SPRN_TIDR, new_thread->tidr); + } +#endif } #ifdef CONFIG_PPC_BOOK3S_64 @@ -1438,9 +1445,117 @@ void flush_thread(void) #endif /* CONFIG_HAVE_HW_BREAKPOINT */ } +#ifdef CONFIG_PPC64 +static DEFINE_SPINLOCK(vas_thread_id_lock); +static DEFINE_IDA(vas_thread_ida); + +/* + * We need to assign a unique thread id to each thread in a process. + * + * This thread id, referred to as TIDR, and separate from the Linux's tgid, + * is intended to be used to direct an ASB_Notify from the hardware to the + * thread, when a suitable event occurs in the system. + * + * One such event is a "paste" instruction in the context of Fast Thread + * Wakeup (aka Core-to-core wake up in the Virtual Accelerator Switchboard + * (VAS) in POWER9. + * + * To get a unique TIDR per process we could simply reuse task_pid_nr() but + * the problem is that task_pid_nr() is not yet available copy_thread() is + * called. Fixing that would require changing more intrusive arch-neutral + * code in code path in copy_process()?. + * + * Further, to assign unique TIDRs within each process, we need an atomic + * field (or an IDR) in task_struct, which again intrudes into the arch- + * neutral code. So try to assign globally unique TIDRs for now. + * + * NOTE: TIDR 0 indicates that the thread does not need a TIDR value. + * For now, only threads that expect to be notified by the VAS + * hardware need a TIDR value and we assign values > 0 for those. + */ +#define MAX_THREAD_CONTEXT ((1 << 16) - 1) +static int assign_thread_tidr(void) +{ + int index; + int err; + +again: + if (!ida_pre_get(&vas_thread_ida, GFP_KERNEL)) + return -ENOMEM; + + spin_lock(&vas_thread_id_lock); + err = ida_get_new_above(&vas_thread_ida, 1, &index); + spin_unlock(&vas_thread_id_lock); + + if (err == -EAGAIN) + goto again; + else if (err) + return err; + + if (index > MAX_THREAD_CONTEXT) { + spin_lock(&vas_thread_id_lock); + ida_remove(&vas_thread_ida, index); + spin_unlock(&vas_thread_id_lock); + return -ENOMEM; + } + + return index; +} + +static void free_thread_tidr(int id) +{ + spin_lock(&vas_thread_id_lock); + ida_remove(&vas_thread_ida, id); + spin_unlock(&vas_thread_id_lock); +} + +/* + * Clear any TIDR value assigned to this thread. + */ +void clear_thread_tidr(struct task_struct *t) +{ + if (!t->thread.tidr) + return; + + if (!cpu_has_feature(CPU_FTR_ARCH_300)) { + WARN_ON_ONCE(1); + return; + } + + mtspr(SPRN_TIDR, 0); + free_thread_tidr(t->thread.tidr); + t->thread.tidr = 0; +} + +/* + * Assign a unique TIDR (thread id) for task @t and set it in the thread + * structure. For now, we only support setting TIDR for 'current' task. + */ +int set_thread_tidr(struct task_struct *t) +{ + if (!cpu_has_feature(CPU_FTR_ARCH_300)) + return -EINVAL; + + if (t != current) + return -EINVAL; + + t->thread.tidr = assign_thread_tidr(); + if (t->thread.tidr < 0) + return t->thread.tidr; + + mtspr(SPRN_TIDR, t->thread.tidr); + + return 0; +} + +#endif /* CONFIG_PPC64 */ + void release_thread(struct task_struct *t) { +#ifdef CONFIG_PPC64 + clear_thread_tidr(t); +#endif } /* @@ -1466,6 +1581,10 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) clear_task_ebb(dst); +#ifdef CONFIG_PPC64 + dst->thread.tidr = 0; +#endif + return 0; } @@ -1576,6 +1695,9 @@ int copy_thread(unsigned long clone_flags, unsigned long usp, #endif setup_ksp_vsid(p, sp); +#ifdef CONFIG_PPC64 + p->thread.tidr = 0; +#endif #ifdef CONFIG_PPC64 if (cpu_has_feature(CPU_FTR_DSCR)) { -- 2.7.4