From patchwork Mon Feb 15 16:06:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pierre Morel X-Patchwork-Id: 12088827 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AEEE3C433E9 for ; Mon, 15 Feb 2021 16:14:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 74A2564DF0 for ; Mon, 15 Feb 2021 16:14:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232305AbhBOQOS (ORCPT ); Mon, 15 Feb 2021 11:14:18 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:20106 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S232089AbhBOQHm (ORCPT ); Mon, 15 Feb 2021 11:07:42 -0500 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 11FG0vQH115031; Mon, 15 Feb 2021 11:06:58 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=pp1; bh=bNbbYdqX2UM/ffxVnvLCVYYfZKicGYi1Id5TkMWq7B4=; b=J8YQ/TPuPP7/vdHzX4Q6amXP5A2Dza+o75IUJSuvWAG3Lov1+i0vpkfUFQvzIhx0LTiN DUiVX0gBiI3IFdPSB0NnKOj/WcNMfVpssAIObksAsK7dR41vHDMAXP67eBAAiTXvt6rF OVWypuQZs3L+V3F4x9YYwRus3w39rKsOtvUxW/gkpTA0jTFYRE/zbY6sOBKeZZarG2IR 5gon9VkpVQguB4UmalggYecyULq5oH7Wcosr3FPpEsDrEwGGDtTwRJINVjcROqX+k3xE 0F7d8v1aDQg/oSphdR9LueICOY3ox59JsiXct+KrnF9AjsWBbHnL60aUKw+jVx9qXn5g Mg== Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 36quumrs27-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 15 Feb 2021 11:06:57 -0500 Received: from m0098419.ppops.net (m0098419.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 11FG114n115137; Mon, 15 Feb 2021 11:06:57 -0500 Received: from ppma06fra.de.ibm.com (48.49.7a9f.ip4.static.sl-reverse.com [159.122.73.72]) by mx0b-001b2d01.pphosted.com with ESMTP id 36quumrs17-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 15 Feb 2021 11:06:57 -0500 Received: from pps.filterd (ppma06fra.de.ibm.com [127.0.0.1]) by ppma06fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 11FFsheD021670; Mon, 15 Feb 2021 16:06:55 GMT Received: from b06cxnps4074.portsmouth.uk.ibm.com (d06relay11.portsmouth.uk.ibm.com [9.149.109.196]) by ppma06fra.de.ibm.com with ESMTP id 36p61h921u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 15 Feb 2021 16:06:55 +0000 Received: from d06av24.portsmouth.uk.ibm.com (mk.ibm.com [9.149.105.60]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 11FG6qXs37290342 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 15 Feb 2021 16:06:52 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C815B4203F; Mon, 15 Feb 2021 16:06:52 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 633E542041; Mon, 15 Feb 2021 16:06:52 +0000 (GMT) Received: from oc3016276355.ibm.com (unknown [9.145.73.68]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 15 Feb 2021 16:06:52 +0000 (GMT) From: Pierre Morel To: kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, cohuck@redhat.com, david@redhat.com, thuth@redhat.com, pmorel@linux.ibm.com Subject: [PATCH v3 1/1] s390:kvm: diag9c forwarding Date: Mon, 15 Feb 2021 17:06:50 +0100 Message-Id: <1613405210-16532-2-git-send-email-pmorel@linux.ibm.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1613405210-16532-1-git-send-email-pmorel@linux.ibm.com> References: <1613405210-16532-1-git-send-email-pmorel@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-02-15_11:2021-02-12,2021-02-15 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 adultscore=0 spamscore=0 mlxscore=0 suspectscore=0 mlxlogscore=999 malwarescore=0 priorityscore=1501 bulkscore=0 clxscore=1015 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102150124 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org When we receive intercept a DIAG_9C from the guest we verify that the target real CPU associated with the virtual CPU designated by the guest is running and if not we forward the DIAG_9C to the target real CPU. To avoid a diag9c storm we allow a maximal rate of diag9c forwarding. The rate is calculated as a count per second defined as a new parameter of the s390 kvm module: diag9c_forwarding_hz . The default value is to not forward diag9c. Signed-off-by: Pierre Morel --- Documentation/virt/kvm/s390-diag.rst | 33 ++++++++++++++++++++++++++++ arch/s390/include/asm/kvm_host.h | 1 + arch/s390/include/asm/smp.h | 1 + arch/s390/kernel/smp.c | 1 + arch/s390/kvm/diag.c | 31 +++++++++++++++++++++++--- arch/s390/kvm/kvm-s390.c | 6 +++++ arch/s390/kvm/kvm-s390.h | 8 +++++++ 7 files changed, 78 insertions(+), 3 deletions(-) diff --git a/Documentation/virt/kvm/s390-diag.rst b/Documentation/virt/kvm/s390-diag.rst index eaac4864d3d6..a6371bc4ea90 100644 --- a/Documentation/virt/kvm/s390-diag.rst +++ b/Documentation/virt/kvm/s390-diag.rst @@ -84,3 +84,36 @@ If the function code specifies 0x501, breakpoint functions may be performed. This function code is handled by userspace. This diagnose function code has no subfunctions and uses no parameters. + + +DIAGNOSE function code 'X'9C - Voluntary Time Slice Yield +--------------------------------------------------------- + +General register 1 contains the target CPU address. + +In a guest of a hypervisor like LPAR, KVM or z/VM using shared host CPUs, +DIAGNOSE with function code 'X'9C may improve system performance by +yielding the host CPU on which the guest CPU is running to be assigned +to another guest CPU, preferably the logical CPU containing the specified +target CPU. + + +DIAG 'X'9C forwarding ++++++++++++++++++++++ + +Under KVM, the guest operating system may send a DIAGNOSE code 'X'9C to +the host when it fails to acquire a spinlock for a virtual CPU +and detects that the host CPU on which the virtual guest CPU owner is +assigned to is not running to try to get this host CPU running and +consequently the guest virtual CPU running and freeing the lock. + +However, on the logical partition the real CPU on which the previously +targeted host CPU is assign may itself not be running. +By forwarding the DIAGNOSE code 'X'9C, initially sent by the guest, +from the host to LPAR hypervisor, this one will hopefully schedule +the host CPU which will let KVM run the target guest CPU. + +diag9c_forwarding_hz + KVM kernel parameter allowing to specify the maximum number of DIAGNOSE + 'X'9C forwarding per second in the purpose of avoiding a DIAGNOSE 'X'9C + forwarding storm. diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index 527776a1f076..cb19508c22fb 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -456,6 +456,7 @@ struct kvm_vcpu_stat { u64 diagnose_44; u64 diagnose_9c; u64 diagnose_9c_ignored; + u64 diagnose_9c_forward; u64 diagnose_258; u64 diagnose_308; u64 diagnose_500; diff --git a/arch/s390/include/asm/smp.h b/arch/s390/include/asm/smp.h index 01e360004481..e317fd4866c1 100644 --- a/arch/s390/include/asm/smp.h +++ b/arch/s390/include/asm/smp.h @@ -63,5 +63,6 @@ extern void __noreturn cpu_die(void); extern void __cpu_die(unsigned int cpu); extern int __cpu_disable(void); extern void schedule_mcck_handler(void); +void notrace smp_yield_cpu(int cpu); #endif /* __ASM_SMP_H */ diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 27c763014114..15e207a671fd 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -422,6 +422,7 @@ void notrace smp_yield_cpu(int cpu) asm volatile("diag %0,0,0x9c" : : "d" (pcpu_devices[cpu].address)); } +EXPORT_SYMBOL(smp_yield_cpu); /* * Send cpus emergency shutdown signal. This gives the cpus the diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c index 5b8ec1c447e1..02c146f9e5cd 100644 --- a/arch/s390/kvm/diag.c +++ b/arch/s390/kvm/diag.c @@ -150,6 +150,19 @@ static int __diag_time_slice_end(struct kvm_vcpu *vcpu) return 0; } +static int forward_cnt; +static unsigned long cur_slice; + +static int diag9c_forwarding_overrun(void) +{ + /* Reset the count on a new slice */ + if (time_after(jiffies, cur_slice)) { + cur_slice = jiffies; + forward_cnt = diag9c_forwarding_hz / HZ; + } + return forward_cnt-- <= 0 ? 1 : 0; +} + static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu) { struct kvm_vcpu *tcpu; @@ -167,9 +180,21 @@ static int __diag_time_slice_end_directed(struct kvm_vcpu *vcpu) if (!tcpu) goto no_yield; - /* target already running */ - if (READ_ONCE(tcpu->cpu) >= 0) - goto no_yield; + /* target guest VCPU already running */ + if (READ_ONCE(tcpu->cpu) >= 0) { + if (!diag9c_forwarding_hz || diag9c_forwarding_overrun()) + goto no_yield; + + /* target host CPU already running */ + if (!vcpu_is_preempted(tcpu->cpu)) + goto no_yield; + smp_yield_cpu(tcpu->cpu); + VCPU_EVENT(vcpu, 5, + "diag time slice end directed to %d: yield forwarded", + tid); + vcpu->stat.diagnose_9c_forward++; + return 0; + } if (kvm_vcpu_yield_to(tcpu) <= 0) goto no_yield; diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 053ef36784e4..c23e22610a89 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -157,6 +157,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { VCPU_STAT("instruction_diag_44", diagnose_44), VCPU_STAT("instruction_diag_9c", diagnose_9c), VCPU_STAT("diag_9c_ignored", diagnose_9c_ignored), + VCPU_STAT("diag_9c_forward", diagnose_9c_forward), VCPU_STAT("instruction_diag_258", diagnose_258), VCPU_STAT("instruction_diag_308", diagnose_308), VCPU_STAT("instruction_diag_500", diagnose_500), @@ -190,6 +191,11 @@ static bool use_gisa = true; module_param(use_gisa, bool, 0644); MODULE_PARM_DESC(use_gisa, "Use the GISA if the host supports it."); +/* maximum diag9c forwarding per second */ +unsigned int diag9c_forwarding_hz; +module_param(diag9c_forwarding_hz, uint, 0644); +MODULE_PARM_DESC(diag9c_forwarding_hz, "Maximum diag9c forwarding per second"); + /* * For now we handle at most 16 double words as this is what the s390 base * kernel handles and stores in the prefix page. If we ever need to go beyond diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h index 79dcd647b378..9fad25109b0d 100644 --- a/arch/s390/kvm/kvm-s390.h +++ b/arch/s390/kvm/kvm-s390.h @@ -471,4 +471,12 @@ void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu, * @kvm: the KVM guest */ void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm); + +/** + * diag9c_forwarding_hz + * + * Set the maximum number of diag9c forwarding per second + */ +extern unsigned int diag9c_forwarding_hz; + #endif