2017-09-08 13:23+0200, Andreas Hartmann: > On 09/08/2017 at 12:58 PM Mason wrote: > > On 08/09/2017 11:58, Andreas Hartmann wrote: > > > >> If AVIC is enabled, I'm usually getting one warning like the one below a > >> few minutes after the VM has been started. > >> > >> What does it mean? > >> > >> There isn't any problem with that VM - it's just working as expected. If > >> AVIC is disabled, the warning doesn't come up and the VM works fine, too. > >> > >> Base is a Ryzen system (RMA'd CPU w/o gcc segfaults meanwhile and X370 > >> chipset (ASUS Prime X370-PRO with Bios 0810)). Linux is 4.9.48. > >> > >> > >> [ 1603.482692] ------------[ cut here ]------------ > >> [ 1603.482702] WARNING: CPU: 1 PID: 2936 at ../arch/x86/kvm/svm.c:1484 avic_vcpu_load+0x162/0x190 [kvm_amd] > >> [ 1603.482703] Modules linked in: sr_mod cdrom uas usb_storage vhost_net tun vhost macvtap macvlan igb dca nf_log_ipv4 nf_log_common xt_LOG ipt_REJECT nf_reject_ipv4 xt_tcpudp nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack iptable_filter ip_tables x_tables vfio_pci vfio_iommu_type1 vfio_virqfd vfio br_netfilter bridge stp llc iscsi_ibft iscsi_boot_sysfs snd_hda_codec_generic snd_hda_codec_hdmi snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep kvm_amd snd_pcm eeepc_wmi asus_wmi kvm sparse_keymap snd_seq rfkill video snd_seq_device mxm_wmi irqbypass snd_timer sp5100_tco i2c_piix4 snd pcspkr e1000e soundcore ptp pps_core fjes pinctrl_amd gpio_amdpt acpi_cpufreq gpio_generic 8250_dw tpm_tis shpchp i2c_designware_platform wmi i2c_designware_core tpm_tis_core button tpm nfsd auth_rp > >> cgss nfs_acl > >> [ 1603.482740] lockd grace sunrpc xfs libcrc32c dm_crypt algif_skcipher af_alg hid_generic usbhid raid1 md_mod amdkfd amd_iommu_v2 crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel radeon i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm serio_raw drm ccp xhci_pci xhci_hcd usbcore aesni_intel aes_x86_64 glue_helper lrw ablk_helper cryptd ata_generic pata_atiixp dm_mirror dm_region_hash dm_log sg thermal dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua > >> [ 1603.482766] CPU: 1 PID: 2936 Comm: CPU 2/KVM Not tainted 4.9.48-1.1-default #1 > >> [ 1603.482767] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 0810 08/01/2017 > >> [ 1603.482768] ffffab614aa4fcb8 ffffffff893c14fa 0000000000000000 0000000000000000 > >> [ 1603.482772] ffffab614aa4fcf8 ffffffff89085da1 000005cc004b6f7f 0000000000000001 > >> [ 1603.482774] c0000007ea4bc001 0000000000000001 000001753dd1e17d ffff9e84ea7e0140 > >> [ 1603.482776] Call Trace: > >> [ 1603.482798] [<ffffffff893c14fa>] dump_stack+0x63/0x89 > >> [ 1603.482804] [<ffffffff89085da1>] __warn+0xd1/0xf0 > >> [ 1603.482809] [<ffffffff89085e8d>] warn_slowpath_null+0x1d/0x20 > >> [ 1603.482813] [<ffffffffc15ade42>] avic_vcpu_load+0x162/0x190 [kvm_amd] > >> [ 1603.482849] [<ffffffffc0950da4>] ? kvm_cpu_has_interrupt+0x44/0x50 [kvm] > >> [ 1603.482852] [<ffffffffc15ae138>] svm_vcpu_unblocking+0x18/0x20 [kvm_amd] > >> [ 1603.482868] [<ffffffffc091b424>] kvm_vcpu_block+0xc4/0x310 [kvm] > >> [ 1603.482889] [<ffffffffc0937fac>] kvm_arch_vcpu_ioctl_run+0x19c/0x400 [kvm] > >> [ 1603.482906] [<ffffffffc091cc42>] kvm_vcpu_ioctl+0x312/0x5e0 [kvm] > >> [ 1603.482913] [<ffffffff8910d10f>] ? do_futex+0x10f/0x510 > >> [ 1603.482916] [<ffffffff8923ec06>] do_vfs_ioctl+0x96/0x5b0 > >> [ 1603.482921] [<ffffffff89249767>] ? __fget+0x77/0xb0 > >> [ 1603.482922] [<ffffffff8923f199>] SyS_ioctl+0x79/0x90 > >> [ 1603.482927] [<ffffffff8900393b>] do_syscall_64+0x5b/0xd0 > >> [ 1603.482932] [<ffffffff89719c2f>] entry_SYSCALL64_slow_path+0x25/0x25 > >> [ 1603.484799] ---[ end trace d24b045704bb6ae7 ]--- > > > > For what it's worth... > > > > http://elixir.free-electrons.com/linux/v4.9.48/source/arch/x86/kvm/svm.c#L1484 > > > > entry = READ_ONCE(*(svm->avic_physical_id_cache)); > > WARN_ON(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK); > > > > Added by commit 8221c13700561 > > > > svm: Manage vcpu load/unload when enable AVIC > > When a vcpu is loaded/unloaded to a physical core, we need to update > > host physical APIC ID information in the Physical APIC-ID table > > accordingly. > > Also, when vCPU is blocking/un-blocking (due to halt instruction), > > we need to make sure that the is-running bit in set accordingly in the > > physical APIC-ID table. > > Thanks - I already found this - but I don't know how to estimate it. > > Should I worry about? Or is it just informative? As it is working > afterwards the same as before, it probably isn't critical? > Could the WARN_ON be removed? I'm thinking this happens if the VCPU is preempted in avic_set_running() after 'svm->avic_is_running = true' and before avic_vcpu_load(). avic_vcpu_load() is then called from both avic_set_running() and svm_vcpu_load(). The warning does not reveal any harmful bug. Disabling preemption in avic_set_running() would allow us to keep the protective warning. (It seems to be slightly better than remembeging and restoring the avic state on sched out/in.) Can you try the following patch? Thanks. diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 968f38dcb864..6b123f375d66 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1572,11 +1572,15 @@ static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run) { struct vcpu_svm *svm = to_svm(vcpu); + preempt_disable(); + svm->avic_is_running = is_run; if (is_run) avic_vcpu_load(vcpu, vcpu->cpu); else avic_vcpu_put(vcpu); + + preempt_enable(); } static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
