Date:   Wed, 8 Dec 2021 23:43:46 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Maxim Levitsky <mlevitsk@redhat.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Joerg Roedel <joro@8bytes.org>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        kvm@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 00/26] KVM: x86: Halt and APICv overhaul
Message-ID: <YbFDMjUdVltTSeHr@google.com>
References: <20211208015236.1616697-1-seanjc@google.com>
 <39c885fc6455dd0aa2f8643e725422851430f9ec.camel@redhat.com>
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In-Reply-To: <39c885fc6455dd0aa2f8643e725422851430f9ec.camel@redhat.com>
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On Thu, Dec 09, 2021, Maxim Levitsky wrote:
> >   KVM: SVM: Remove unnecessary APICv/AVIC update in vCPU unblocking path

...

> Probably just luck (can't reproduce this anymore) but
> while running some kvm unit tests with this patch series (and few my patches
> for AVIC co-existance which shouldn't affect this) I got this
> 
> (warning about is_running already set)

My best guess would be the above commit that dropped the handling in the unblock
path, but I haven't been able to concoct a scenario where avic_physical_id_cache
can get out of sync with respect to kvm_vcpu_apicv_active().

> Dec 08 22:53:26 amdlaptop kernel: ------------[ cut here ]------------
> Dec 08 22:53:26 amdlaptop kernel: WARNING: CPU: 3 PID: 72804 at arch/x86/kvm/svm/avic.c:1045 avic_vcpu_load+0xe3/0x100 [kvm_amd]
> Dec 08 22:53:26 amdlaptop kernel: Modules linked in: kvm_amd(O) ccp rng_core kvm(O) irqbypass xt_conntrack ip6table_filter ip6_tables snd_soc_dmic snd_acp3x_>
> Dec 08 22:53:26 amdlaptop kernel:  r8169 realtek 8250_pci usbmon nbd fuse autofs4 [last unloaded: rng_core]
> Dec 08 22:53:26 amdlaptop kernel: CPU: 3 PID: 72804 Comm: qemu-system-i38 Tainted: G           O      5.16.0-rc4.unstable #6
> Dec 08 22:53:26 amdlaptop kernel: Hardware name: LENOVO 20UF001CUS/20UF001CUS, BIOS R1CET65W(1.34 ) 06/17/2021
> Dec 08 22:53:26 amdlaptop kernel: RIP: 0010:avic_vcpu_load+0xe3/0x100 [kvm_amd]
> Dec 08 22:53:26 amdlaptop kernel: Code: 0d 9f e0 85 c0 74 e8 4c 89 f6 4c 89 ff e8 a5 99 f4 e0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 0b 5b 41 5c 41 5d 41 5e 41 >
> Dec 08 22:53:26 amdlaptop kernel: RSP: 0018:ffffc9000b17bba8 EFLAGS: 00010247
> Dec 08 22:53:26 amdlaptop kernel: RAX: 6f63203a756d6571 RBX: ffff888106194740 RCX: ffff88812e7ac000
> Dec 08 22:53:26 amdlaptop kernel: RDX: ffff8883ff6c0000 RSI: 0000000000000003 RDI: 0000000000000003
> Dec 08 22:53:26 amdlaptop kernel: RBP: ffffc9000b17bbd0 R08: ffff888106194740 R09: 0000000000000000
> Dec 08 22:53:26 amdlaptop kernel: R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000003
> Dec 08 22:53:26 amdlaptop kernel: R13: 0000000000000003 R14: ffff88810023b060 R15: dead000000000100
> Dec 08 22:53:26 amdlaptop kernel: FS:  0000000000000000(0000) GS:ffff8883ff6c0000(0000) knlGS:0000000000000000
> Dec 08 22:53:26 amdlaptop kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> Dec 08 22:53:26 amdlaptop kernel: CR2: 00005587e812f958 CR3: 0000000105f31000 CR4: 0000000000350ee0
> Dec 08 22:53:26 amdlaptop kernel: DR0: 00000000004008da DR1: 0000000000000000 DR2: 0000000000000000
> Dec 08 22:53:26 amdlaptop kernel: DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Dec 08 22:53:26 amdlaptop kernel: Call Trace:
> Dec 08 22:53:26 amdlaptop kernel:  <TASK>
> Dec 08 22:53:26 amdlaptop kernel:  svm_vcpu_load+0x56/0x60 [kvm_amd]
> Dec 08 22:53:26 amdlaptop kernel:  kvm_arch_vcpu_load+0x32/0x210 [kvm]
> Dec 08 22:53:26 amdlaptop kernel:  vcpu_load+0x34/0x40 [kvm]
> Dec 08 22:53:26 amdlaptop kernel:  kvm_arch_destroy_vm+0xd4/0x1c0 [kvm]
> Dec 08 22:53:26 amdlaptop kernel:  kvm_destroy_vm+0x163/0x250 [kvm]
> Dec 08 22:53:26 amdlaptop kernel:  kvm_put_kvm+0x26/0x40 [kvm]
> Dec 08 22:53:26 amdlaptop kernel:  kvm_vm_release+0x22/0x30 [kvm]
> Dec 08 22:53:26 amdlaptop kernel:  __fput+0x94/0x250
> Dec 08 22:53:26 amdlaptop kernel:  ____fput+0xe/0x10
> Dec 08 22:53:26 amdlaptop kernel:  task_work_run+0x63/0xa0
> Dec 08 22:53:26 amdlaptop kernel:  do_exit+0x358/0xa30
> Dec 08 22:53:26 amdlaptop kernel:  do_group_exit+0x3b/0xa0
> Dec 08 22:53:26 amdlaptop kernel:  get_signal+0x15b/0x880
> Dec 08 22:53:26 amdlaptop kernel:  ? _copy_to_user+0x20/0x30
> Dec 08 22:53:26 amdlaptop kernel:  ? put_timespec64+0x3d/0x60
> Dec 08 22:53:26 amdlaptop kernel:  arch_do_signal_or_restart+0x106/0x740
> Dec 08 22:53:26 amdlaptop kernel:  ? hrtimer_nanosleep+0x9f/0x120
> Dec 08 22:53:26 amdlaptop kernel:  ? __hrtimer_init+0xd0/0xd0
> Dec 08 22:53:26 amdlaptop kernel:  exit_to_user_mode_prepare+0x112/0x1f0
> Dec 08 22:53:26 amdlaptop kernel:  syscall_exit_to_user_mode+0x17/0x40
> Dec 08 22:53:26 amdlaptop kernel:  do_syscall_64+0x42/0x80
> Dec 08 22:53:26 amdlaptop kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xae
> Dec 08 22:53:26 amdlaptop kernel: RIP: 0033:0x7f537abb13b5
> Dec 08 22:53:26 amdlaptop kernel: Code: Unable to access opcode bytes at RIP 0x7f537abb138b.
> Dec 08 22:53:26 amdlaptop kernel: RSP: 002b:00007f5376a39680 EFLAGS: 00000293 ORIG_RAX: 00000000000000e6
> Dec 08 22:53:26 amdlaptop kernel: RAX: fffffffffffffdfc RBX: 00007f5376a396d0 RCX: 00007f537abb13b5
> Dec 08 22:53:26 amdlaptop kernel: RDX: 00007f5376a396d0 RSI: 0000000000000000 RDI: 0000000000000000
> Dec 08 22:53:26 amdlaptop kernel: RBP: 00007f5376a396c0 R08: 0000000000000000 R09: 0000000000000000
> Dec 08 22:53:26 amdlaptop kernel: R10: 00007f5376a396c0 R11: 0000000000000293 R12: 00007f5376a3b640
> Dec 08 22:53:26 amdlaptop kernel: R13: 0000000000000002 R14: 00007f537ab66880 R15: 0000000000000000
> Dec 08 22:53:26 amdlaptop kernel:  </TASK>
> Dec 08 22:53:26 amdlaptop kernel: ---[ end trace 676058aaf29d0267 ]---
> 
> 
> I'll post my patches tomorrow, after some more testing.
> 
> Best regards,
> 	Maxim Levitsky
>