Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753349AbdLNP2Q (ORCPT ); Thu, 14 Dec 2017 10:28:16 -0500 Received: from mail-pf0-f195.google.com ([209.85.192.195]:33406 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753099AbdLNP2M (ORCPT ); Thu, 14 Dec 2017 10:28:12 -0500 X-Google-Smtp-Source: ACJfBosTKqWDe/yaZ8DO9zag0wiAZNmekxth8AW3RYxsjlolUTUKvL3gmnzJsuqB6rmhqtzHk8LQ8A== Subject: Re: [PATCH] KVM: arm/arm64: don't set vtimer->cnt_ctl in kvm_arch_timer_handler To: Christoffer Dall Cc: Marc Zyngier , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, Jia He References: <1513148407-2611-1-git-send-email-hejianet@gmail.com> <20171213091803.GQ910@cbox> <20171214130954.GV910@cbox> From: Jia He Message-ID: <5615f3e1-756e-0537-f0b6-20ae8626ac87@gmail.com> Date: Thu, 14 Dec 2017 23:28:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20171214130954.GV910@cbox> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7101 Lines: 162 Hi Christoffer On 12/14/2017 9:09 PM, Christoffer Dall Wrote: > On Thu, Dec 14, 2017 at 12:57:54PM +0800, Jia He wrote: > Hi Jia, > >> I have tried your newer level-mapped-v7 branch, but bug is still there. >> >> There is no special load in both host and guest. The guest (kernel >> 4.14) is often hanging when booting >> >> the guest kernel log >> >> [ OK ] Reached target Remote File Systems. >> Starting File System Check on /dev/mapper/fedora-root... >> [ OK ] Started File System Check on /dev/mapper/fedora-root. >> Mounting /sysroot... >> [ 2.670764] SGI XFS with ACLs, security attributes, no debug enabled >> [ 2.678180] XFS (dm-0): Mounting V5 Filesystem >> [ 2.740364] XFS (dm-0): Ending clean mount >> [ OK ] Mounted /sysroot. >> [ OK ] Reached target Initrd Root File System. >> Starting Reload Configuration from the Real Root... >> [ 61.288215] INFO: rcu_sched detected stalls on CPUs/tasks: >> [ 61.290791] 1-...!: (0 ticks this GP) idle=574/0/0 softirq=5/5 fqs=1 >> [ 61.293664] (detected by 0, t=6002 jiffies, g=-263, c=-264, q=39760) >> [ 61.296480] Task dump for CPU 1: >> [ 61.297938] swapper/1 R running task 0 0 1 0x00000020 >> [ 61.300643] Call trace: >> [ 61.301260] __switch_to+0x6c/0x78 >> [ 61.302095] cpu_number+0x0/0x8 >> [ 61.302867] rcu_sched kthread starved for 6000 jiffies! >> g18446744073709551353 c18446744073709551352 f0x0 RCU_GP_WAIT_FQS(3) >> ->state=0x402 ->cpu=1 >> [ 61.305941] rcu_sched I 0 8 2 0x00000020 >> [ 61.307250] Call trace: >> [ 61.307854] __switch_to+0x6c/0x78 >> [ 61.308693] __schedule+0x268/0x8f0 >> [ 61.309545] schedule+0x2c/0x88 >> [ 61.310325] schedule_timeout+0x84/0x3b8 >> [ 61.311278] rcu_gp_kthread+0x4d4/0x7d8 >> [ 61.312213] kthread+0x134/0x138 >> [ 61.313001] ret_from_fork+0x10/0x1c >> >> Maybe my previous patch is not perfect enough, thanks for your comments. >> >> I digged it futher more, do you think below code logic is possibly >> problematic? >> >> >> vtimer_save_state           (vtimer->loaded = false, cntv_ctl is 0) >> >> kvm_arch_timer_handler        (read cntv_ctl and set vtimer->cnt_ctl = 0) >> >> vtimer_restore_state            (write vtimer->cnt_ctl to cntv_ctl, >> then cntv_ctl will >> >>                        be 0 forever) >> >> >> If above analysis is reasonable > Yes, I think there's something there if the hardware doesn't retire the > signal fast enough... > >> how about below patch? already >> tested in my arm64 server. >> >> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c >> index f9555b1..ee6dd3f 100644 >> --- a/virt/kvm/arm/arch_timer.c >> +++ b/virt/kvm/arm/arch_timer.c >> @@ -99,7 +99,7 @@ static irqreturn_t kvm_arch_timer_handler(int irq, >> void *dev_id) >>         } >>         vtimer = vcpu_vtimer(vcpu); >> >> -       if (!vtimer->irq.level) { >> +       if (vtimer->loaded && !vtimer->irq.level) { >>                 vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl); >>                 if (kvm_timer_irq_can_fire(vtimer)) >>                         kvm_timer_update_irq(vcpu, true, vtimer); >> > There's nothing really wrong with that patch, I just didn't think it > would be necessary, as we really shouldn't see interrupts if the timer > is not loaded. Can you confirm that a WARN_ON(!vtimer->loaded) in > kvm_arch_timer_handler() gives you a splat? Please see the WARN_ON result (without my patch) [   72.171706] WARNING: CPU: 24 PID: 1768 at arch/arm64/kvm/../../../virt/kvm/arm/arch_timer.c:101 kvm_arch_timer_handler+0xc0/0xc8 [   72.182305] Modules linked in: vhost_net tap xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge stp llc ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter ip_tables x_tables vhost_scsi vhost tcm_qla2xxx qla2xxx nvme_fc nvme_fabrics tcm_fc libfc scsi_transport_fc ib_srpt ib_cm ib_core iscsi_target_mod tcm_loop target_core_file target_core_iblock target_core_pscsi target_core_mod binfmt_misc nls_iso8859_1 shpchp crc32_ce crct10dif_ce i2c_qup dm_multipath autofs4 btrfs zstd_decompress zstd_compress xxhash raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear at803x ixgbe [   72.252877]  xhci_plat_hcd xhci_hcd usbcore qcom_emac mdio ahci_platform libahci_platform libahci [   72.261733] CPU: 24 PID: 1768 Comm: qemu-system-aar Tainted: G        W        4.15.0-rc3+ #128 [   72.270412] Hardware name: WIWYNN QDF2400 Reference Evaluation Platform CV90-LA115-P151/QDF2400 Customer Reference Board, BIOS 0ACJA425 09/07/2017 [   72.283520] pstate: 80400085 (Nzcv daIf +PAN -UAO) [   72.288295] pc : kvm_arch_timer_handler+0xc0/0xc8 [   72.292984] lr : handle_percpu_devid_irq+0x8c/0x230 [   72.297842] sp : ffff00000830ff00 [   72.301141] x29: ffff00000830ff00 x28: ffffc17b9feaff00 [   72.306436] x27: ffff2e7462531000 x26: ffff000008310000 [   72.311731] x25: ffff000008300000 x24: ffffc17b80069100 [   72.317026] x23: 0000000000000003 x22: ffff2e74632248e8 [   72.322321] x21: ffffc17b80054c00 x20: 0000000000000000 [   72.327616] x19: ffffc17b8ac37dc0 x18: 0000000000000010 [   72.332911] x17: 000000000000000a x16: 0000000000007fff [   72.338207] x15: ffffffffffffffff x14: 6d202c6666666666 [   72.343502] x13: 6666667830203a73 x12: 656c6379635f7861 [   72.348797] x11: ffff000009395448 x10: ffff00000862b5b8 [   72.354092] x9 : 0000000000000040 x8 : ffffc17b60007238 [   72.359387] x7 : 0000000000000000 x6 : ffffc17b80054c00 [   72.364682] x5 : ffffc17b60007250 x4 : 0000930756ce0000 [   72.369977] x3 : ffff2e74619cfff0 x2 : 0000930756ce0000 [   72.375273] x1 : 0000000000000000 x0 : ffffc17b8ac399c0 [   72.380568] Call trace: [   72.383000]  kvm_arch_timer_handler+0xc0/0xc8 [   72.387340]  handle_percpu_devid_irq+0x8c/0x230 [   72.391853]  generic_handle_irq+0x34/0x50 [   72.395846]  __handle_domain_irq+0x68/0xc0 [   72.399926]  gic_handle_irq+0xcc/0x188 [   72.403658]  el1_irq+0xd8/0x180 [   72.406785]  hrtimer_try_to_cancel+0x0/0x160 [   72.411037]  kvm_timer_vcpu_put+0x3c/0x50 [   72.415030]  kvm_arch_vcpu_put+0x20/0x50 [   72.418937]  vcpu_put+0x20/0x40 [   72.422061]  kvm_vcpu_ioctl+0x244/0x7b8 [   72.425882]  do_vfs_ioctl+0xc4/0x988 [   72.429440]  SyS_ioctl+0x94/0xa8 [   72.432652]  el0_svc_naked+0x20/0x24 [   72.436210] ---[ end trace 11d0c8bba284e766 ]--- > Also, could you give the following a try (without your patch): > > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c > index 73d262c4712b..4751255345d1 100644 > --- a/virt/kvm/arm/arch_timer.c > +++ b/virt/kvm/arm/arch_timer.c > @@ -367,6 +367,7 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu) > > /* Disable the virtual timer */ > write_sysreg_el0(0, cntv_ctl); > + isb(); No luck， the bug is still there Cheers, Jia