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Mon, 18 Jan 2021 13:17:40 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 41DDF42041; Mon, 18 Jan 2021 13:17:40 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 27D1742049; Mon, 18 Jan 2021 13:17:40 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.152.85.9]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 18 Jan 2021 13:17:40 +0000 (GMT) Received: by tuxmaker.boeblingen.de.ibm.com (Postfix, from userid 25651) id D74A5E0A39; Mon, 18 Jan 2021 14:17:39 +0100 (CET) From: Christian Borntraeger To: Janosch Frank Cc: KVM , Cornelia Huck , Christian Borntraeger , David Hildenbrand , linux-s390 , Pierre Morel , Thomas Huth Subject: [PATCH 1/1] KVM: s390: diag9c forwarding Date: Mon, 18 Jan 2021 14:17:39 +0100 Message-Id: <20210118131739.7272-2-borntraeger@de.ibm.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20210118131739.7272-1-borntraeger@de.ibm.com> References: <20210118131739.7272-1-borntraeger@de.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.343,18.0.737 definitions=2021-01-18_11:2021-01-18,2021-01-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 lowpriorityscore=0 phishscore=0 priorityscore=1501 mlxscore=0 clxscore=1015 spamscore=0 malwarescore=0 mlxlogscore=999 suspectscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101180077 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Pierre Morel 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 Signed-off-by: Christian Borntraeger --- 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 ++++++++ 6 files changed, 45 insertions(+), 3 deletions(-) diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index 74f9a036bab2..98ae55f79620 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -455,6 +455,7 @@ 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 c5abbb94ac6e..32622e9c15f0 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..fc1ec4aa81ed 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 unsigned 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-- ? 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 VCPU already running */ + if (READ_ONCE(tcpu->cpu) >= 0) { + if (!diag9c_forwarding_hz || diag9c_forwarding_overrun()) + goto no_yield; + + /* target 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 759bbc012b6c..9b98db81db31 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -158,6 +158,7 @@ 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), @@ -191,6 +192,11 @@ 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