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Mon, 4 May 2026 12:48:23 +0000 (GMT) Message-ID: Date: Mon, 4 May 2026 14:48:22 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [v5 1/3] KVM: setup empty irq routing when create vm To: Paolo Bonzini , Yi Wang , seanjc@google.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, wanpengli@tencent.com, foxywang@tencent.com, oliver.upton@linux.dev, maz@kernel.org, anup@brainfault.org, atishp@atishpatra.org, frankja@linux.ibm.com, imbrenda@linux.ibm.com, weijiang.yang@intel.com, Parshuram Sangle , Sean Christopherson References: <20240506101751.3145407-1-foxywang@tencent.com> <20240506101751.3145407-2-foxywang@tencent.com> <7e958b82-4eb1-4d61-b301-dde6a19312ba@linux.ibm.com> <280451fd-63e9-44b0-9f56-d39dd01861b9@linux.ibm.com> <57d1130f-0375-4934-9820-2edbc3860ee1@redhat.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <57d1130f-0375-4934-9820-2edbc3860ee1@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA0MDEzNCBTYWx0ZWRfX0BK9pf7sWiKk BenRpA2Hw6YpcSzUHjlp3bdVsWTs2xkFJhxlMIRIwbNeBHoW+ZmxjpC3S0F0KNF/Bc/KmiGIBlo 1j3496zRlgbsbUaqgS/c1Pr+yeBov4BtWWYWExkUXREVhbgJ1aaErB0+kCWGTaMiJX8vKALLdTU igACw8fPjfdUHCy5c6LLI0BAPrkFThbmDGC9aKeiu6p43giTYYohjc/xJnfXVpsneHJEkAX7w/I 2egiMvfVuZ1FnMx3NThLKzxvCErNzFkmxyfUfaRchWSKmkc0PpwN5Lu+9EClKrFBGaFJM+uojR2 3NjOdBeALO3/3ArLG764igGVtdY3lgYhszRajmwc2st4gOHnio0YaFw7FVlig8Gtx/3kGIsv1ZO YdrruxPtHKn3JQqI7kcZQ7w5YSIhSenVvSHpJ++fRmYudOwLdQDHKERmddUlhnR0Va+sh41u/vL wROmXdw2WzDDBFMXE5g== X-Proofpoint-ORIG-GUID: srMHMhmb0VQN6y_ONtyOtSMZMiuazi3Y X-Proofpoint-GUID: TLlny7jaqKay16AX29ifsTVV0fV-cAV9 X-Authority-Analysis: v=2.4 cv=W7UIkxWk c=1 sm=1 tr=0 ts=69f8959f cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=bTDSsSjtds8SPOVyGFwA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-04_04,2026-04-30_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 malwarescore=0 suspectscore=0 spamscore=0 clxscore=1011 phishscore=0 bulkscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605040134 Am 17.04.26 um 12:19 schrieb Paolo Bonzini: > On 4/17/26 11:36, Christian Borntraeger wrote: >>> >>> >>>          irq_rt = srcu_dereference_check(kvm->irq_routing, &kvm- >irq_srcu, >>>                                          lockdep_is_held(&kvm- >irq_lock)); >>>          if (irq_rt && gsi < irq_rt->nr_rt_entries) {  <--------- >>> >> Hmm, I guess I misread the code and the problem is likely not this. >> Let me have another look. > > It makes sense anyway, together with a similar extra element in > kvm_set_irq_routing(): Turns out that the bisect was wrong. the increased cpu consumption came from commit aeb1b22a3ac8e94c791f06f16e921384794771fa ("KVM: Enable halt polling shrink parameter by default") which kind of makes sense. @Paolo, shall I do a patch with 0 nr_rt_entries anyway as discussed or shall we drop this? > > diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c > index 462c70621247..c3e4fbbfed94 100644 > --- a/virt/kvm/irqchip.c > +++ b/virt/kvm/irqchip.c > @@ -178,11 +178,9 @@ int kvm_set_irq_routing(struct kvm *kvm, >      for (i = 0; i < nr; ++i) { >          if (ue[i].gsi >= KVM_MAX_IRQ_ROUTES) >              return -EINVAL; > -        nr_rt_entries = max(nr_rt_entries, ue[i].gsi); > +        nr_rt_entries = max(nr_rt_entries + 1, ue[i].gsi); >      } > > -    nr_rt_entries += 1; > - >      new = kzalloc_flex(*new, map, nr_rt_entries, GFP_KERNEL_ACCOUNT); >      if (!new) >          return -ENOMEM; > @@ -246,11 +244,11 @@ int kvm_init_irq_routing(struct kvm *kvm) >      struct kvm_irq_routing_table *new; >      int chip_size; > > -    new = kzalloc_flex(*new, map, 1, GFP_KERNEL_ACCOUNT); > +    new = kzalloc_flex(*new, map, 0, GFP_KERNEL_ACCOUNT); >      if (!new) >          return -ENOMEM; > > -    new->nr_rt_entries = 1; > +    new->nr_rt_entries = 0; > >      chip_size = sizeof(int) * KVM_NR_IRQCHIPS * KVM_IRQCHIP_NUM_PINS; >      memset(new->chip, -1, chip_size); > > Paolo >