From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3s9PNg4yFTzDr5g for ; Fri, 12 Aug 2016 09:29:07 +1000 (AEST) Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u7BNSeT2080427 for ; Thu, 11 Aug 2016 19:29:05 -0400 Received: from e23smtp04.au.ibm.com (e23smtp04.au.ibm.com [202.81.31.146]) by mx0a-001b2d01.pphosted.com with ESMTP id 24qm9v829c-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 11 Aug 2016 19:29:05 -0400 Received: from localhost by e23smtp04.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 12 Aug 2016 09:29:03 +1000 Received: from d23relay07.au.ibm.com (d23relay07.au.ibm.com [9.190.26.37]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 51D793578053 for ; Fri, 12 Aug 2016 09:29:00 +1000 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay07.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u7BNT07n30474346 for ; Fri, 12 Aug 2016 09:29:00 +1000 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u7BNT01k028149 for ; Fri, 12 Aug 2016 09:29:00 +1000 From: Cyril Bur To: linuxppc-dev@lists.ozlabs.org, wei.guo.simon@gmail.com Cc: anton@samba.org, mikey@neuling.org Subject: [PATCH v2 02/20] powerpc: Always restore FPU/VEC/VSX if hardware transactional memory in use Date: Fri, 12 Aug 2016 09:28:01 +1000 In-Reply-To: <20160811232819.11453-1-cyrilbur@gmail.com> References: <20160811232819.11453-1-cyrilbur@gmail.com> Message-Id: <20160811232819.11453-3-cyrilbur@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Comment from arch/powerpc/kernel/process.c:967: If userspace is inside a transaction (whether active or suspended) and FP/VMX/VSX instructions have ever been enabled inside that transaction, then we have to keep them enabled and keep the FP/VMX/VSX state loaded while ever the transaction continues. The reason is that if we didn't, and subsequently got a FP/VMX/VSX unavailable interrupt inside a transaction, we don't know whether it's the same transaction, and thus we don't know which of the checkpointed state and the ransactional state to use. restore_math() restore_fp() and restore_altivec() currently may not restore the registers. It doesn't appear that this is more serious than a performance penalty. If the math registers aren't restored the userspace thread will still be run with the facility disabled. Userspace will not be able to read invalid values. On the first access it will take an facility unavailable exception and the kernel will detected an active transaction, at which point it will abort the transaction. There is the possibility for a pathological case preventing any progress by transactions, however, transactions are never guaranteed to make progress. Fixes: 70fe3d9 ("powerpc: Restore FPU/VEC/VSX if previously used") Signed-off-by: Cyril Bur --- arch/powerpc/kernel/process.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 58ccf86..a5cdef9 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -208,7 +208,7 @@ void enable_kernel_fp(void) EXPORT_SYMBOL(enable_kernel_fp); static int restore_fp(struct task_struct *tsk) { - if (tsk->thread.load_fp) { + if (tsk->thread.load_fp || MSR_TM_ACTIVE(tsk->thread.regs->msr)) { load_fp_state(¤t->thread.fp_state); current->thread.load_fp++; return 1; @@ -278,7 +278,8 @@ EXPORT_SYMBOL_GPL(flush_altivec_to_thread); static int restore_altivec(struct task_struct *tsk) { - if (cpu_has_feature(CPU_FTR_ALTIVEC) && tsk->thread.load_vec) { + if (cpu_has_feature(CPU_FTR_ALTIVEC) && + (tsk->thread.load_vec || MSR_TM_ACTIVE(tsk->thread.regs->msr))) { load_vr_state(&tsk->thread.vr_state); tsk->thread.used_vr = 1; tsk->thread.load_vec++; @@ -464,7 +465,8 @@ void restore_math(struct pt_regs *regs) { unsigned long msr; - if (!current->thread.load_fp && !loadvec(current->thread)) + if (!MSR_TM_ACTIVE(regs->msr) && + !current->thread.load_fp && !loadvec(current->thread)) return; msr = regs->msr; -- 2.9.2