From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752127AbdKICwS (ORCPT ); Wed, 8 Nov 2017 21:52:18 -0500 Received: from mail-pf0-f194.google.com ([209.85.192.194]:52341 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751470AbdKICwQ (ORCPT ); Wed, 8 Nov 2017 21:52:16 -0500 X-Google-Smtp-Source: ABhQp+RtguiWiR/Fjv/2yHuh6p0dMBSuFHoIbYitXbmLbvQe7ONl3UOgZRy+OhOseSYYKXWppWWfeg== From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Wanpeng Li Subject: [PATCH v3] KVM: X86: Fix softlockup when get the current kvmclock Date: Wed, 8 Nov 2017 18:52:12 -0800 Message-Id: <1510195932-6232-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [qemu-system-x86:10185] CPU: 6 PID: 10185 Comm: qemu-system-x86 Tainted: G OE 4.14.0-rc4+ #4 RIP: 0010:kvm_get_time_scale+0x4e/0xa0 [kvm] Call Trace: ? get_kvmclock_ns+0xa3/0x140 [kvm] get_time_ref_counter+0x5a/0x80 [kvm] kvm_hv_process_stimers+0x120/0x5f0 [kvm] ? kvm_hv_process_stimers+0x120/0x5f0 [kvm] ? preempt_schedule+0x27/0x30 ? ___preempt_schedule+0x16/0x18 kvm_arch_vcpu_ioctl_run+0x4b4/0x1690 [kvm] ? kvm_arch_vcpu_load+0x47/0x230 [kvm] kvm_vcpu_ioctl+0x33a/0x620 [kvm] ? kvm_vcpu_ioctl+0x33a/0x620 [kvm] ? kvm_vm_ioctl_check_extension_generic+0x3b/0x40 [kvm] ? kvm_dev_ioctl+0x279/0x6c0 [kvm] do_vfs_ioctl+0xa1/0x5d0 ? __fget+0x73/0xa0 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x1e/0xa9 This can be reproduced when running kvm-unit-tests/hyperv_stimer.flat and cpu-hotplug stress simultaneously. __this_cpu_read(cpu_tsc_khz) returns 0 (set in kvmclock_cpu_down_prep()) when the pCPU is unhotplug which results in kvm_get_time_scale() gets into an infinite loop. This patch fixes it by treating the unhotplug pCPU as not using master clock. Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li --- arch/x86/kvm/x86.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 03869eb..d61dcce3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1795,10 +1795,13 @@ u64 get_kvmclock_ns(struct kvm *kvm) /* both __this_cpu_read() and rdtsc() should be on the same cpu */ get_cpu(); - kvm_get_time_scale(NSEC_PER_SEC, __this_cpu_read(cpu_tsc_khz) * 1000LL, - &hv_clock.tsc_shift, - &hv_clock.tsc_to_system_mul); - ret = __pvclock_read_cycles(&hv_clock, rdtsc()); + if (__this_cpu_read(cpu_tsc_khz)) { + kvm_get_time_scale(NSEC_PER_SEC, __this_cpu_read(cpu_tsc_khz) * 1000LL, + &hv_clock.tsc_shift, + &hv_clock.tsc_to_system_mul); + ret = __pvclock_read_cycles(&hv_clock, rdtsc()); + } else + ret = ktime_get_boot_ns() + ka->kvmclock_offset; put_cpu(); -- 2.7.4