From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751948AbcF1Djy (ORCPT ); Mon, 27 Jun 2016 23:39:54 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:49496 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751764AbcF1Djx (ORCPT ); Mon, 27 Jun 2016 23:39:53 -0400 X-IBM-Helo: d23dlp01.au.ibm.com X-IBM-MailFrom: xinhui.pan@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Tue, 28 Jun 2016 11:39:18 +0800 From: xinhui User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: Boqun Feng CC: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, peterz@infradead.org, mingo@redhat.com, mpe@ellerman.id.au, paulus@samba.org, benh@kernel.crashing.org, Waiman.Long@hpe.com, will.deacon@arm.com, dave@stgolabs.net Subject: Re: [PATCH 2/3] powerpc/spinlock: support vcpu preempted check References: <1467049290-32359-1-git-send-email-xinhui.pan@linux.vnet.ibm.com> <1467049290-32359-3-git-send-email-xinhui.pan@linux.vnet.ibm.com> <20160627145832.GB19108@insomnia> In-Reply-To: <20160627145832.GB19108@insomnia> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16062803-0016-0000-0000-000001AB3787 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16062803-0017-0000-0000-000004E7B127 Message-Id: <5771F166.5060604@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-28_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1606280033 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016年06月27日 22:58, Boqun Feng wrote: > Hi Xinhui, > > On Mon, Jun 27, 2016 at 01:41:29PM -0400, Pan Xinhui wrote: >> This is to fix some holder preemption issues. Spinning at one >> vcpu which is preempted is meaningless. >> >> Kernel need such interfaces, So lets support it. >> >> We also should suooprt both the shared and dedicated mode. >> So add lppaca_dedicated_proc macro in lppaca.h >> >> Suggested-by: Boqun Feng >> Signed-off-by: Pan Xinhui >> --- >> arch/powerpc/include/asm/lppaca.h | 6 ++++++ >> arch/powerpc/include/asm/spinlock.h | 15 +++++++++++++++ >> 2 files changed, 21 insertions(+) >> >> diff --git a/arch/powerpc/include/asm/lppaca.h b/arch/powerpc/include/asm/lppaca.h >> index d0a2a2f..0a263d3 100644 >> --- a/arch/powerpc/include/asm/lppaca.h >> +++ b/arch/powerpc/include/asm/lppaca.h >> @@ -111,12 +111,18 @@ extern struct lppaca lppaca[]; >> * we will have to transition to something better. >> */ >> #define LPPACA_OLD_SHARED_PROC 2 >> +#define LPPACA_OLD_DEDICATED_PROC (1 << 6) >> > > I think you should describe a little bit about the magic number here, right. > i.e. what document/specification says this should work, and how this > works. > yep, I need add some comments here. for example, this bit is firmware reserved... thanks, will do that. >> static inline bool lppaca_shared_proc(struct lppaca *l) >> { >> return !!(l->__old_status & LPPACA_OLD_SHARED_PROC); >> } >> >> +static inline bool lppaca_dedicated_proc(struct lppaca *l) >> +{ >> + return !!(l->__old_status & LPPACA_OLD_DEDICATED_PROC); >> +} >> + >> /* >> * SLB shadow buffer structure as defined in the PAPR. The save_area >> * contains adjacent ESID and VSID pairs for each shadowed SLB. The >> diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h >> index 523673d..ae938ee 100644 >> --- a/arch/powerpc/include/asm/spinlock.h >> +++ b/arch/powerpc/include/asm/spinlock.h >> @@ -52,6 +52,21 @@ >> #define SYNC_IO >> #endif >> >> +/* For fixing some spinning issues in a guest. >> + * kernel would check if vcpu is preempted during a spin loop. >> + * we support that. >> + */ >> +#define arch_vcpu_is_preempted arch_vcpu_is_preempted >> +static inline bool arch_vcpu_is_preempted(int cpu) > > This function should be guarded by #ifdef PPC_PSERIES .. #endif, right? > Because if the kernel is not compiled with guest support, > vcpu_is_preempted() should always be false, right? > oh, I forgot that. thanks for pointing it out. >> +{ >> + struct lppaca *lp = &lppaca_of(cpu); >> + >> + if (unlikely(!(lppaca_shared_proc(lp) || >> + lppaca_dedicated_proc(lp)))) > > Do you want to detect whether we are running in a guest(ie. pseries > kernel) here? Then I wonder whether "machine_is(pseries)" works here. > I tried as you said yesterday. but .h file has dependencies. As you said, if we add #ifdef PPC_PSERIES, this is not a big problem. only powernv will be affected as they are built into same kernel img. > Regards, > Boqun > >> + return false; >> + return !!(be32_to_cpu(lp->yield_count) & 1); >> +} >> + >> static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) >> { >> return lock.slock == 0; >> -- >> 2.4.11 >>