From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x2240rmPo5UtJTU0usMjHiMP4Hw2xSS5qUdu5vcNWUSyq00ayAHZf53QfvVbaMN+OMmzPsVEn ARC-Seal: i=1; a=rsa-sha256; t=1517591056; cv=none; d=google.com; s=arc-20160816; b=OS9fa4tK3hDm3a9wxNVUpLYLMnmhyl8Rj+T/9aCio/12mdAFefKGmcEXgO3G1XyqrO QBcI2fZLQBU73gI67SG2C+wRCVQWFOVRC2dsDiIJ3faHMNZYmmmO3ktpK/PaHX53X9Q3 FHyDYXwBH66PemXP/L3UISK2brs5dSjIRWTUzS9WSBQ/bOYWPpBhjjog2nYrhTP1oOaf 8b/DzhXEDNtWm43xlVtf7U4+JR0abmr8Bj7Bn9VAvKCFQsY0dAD5b7ZsWuFpZd82ha/B GtC6olGZU1xzkE7QTruNdrIaIzXSsiNdSjjR8SbJHpZxBjSUqFfvtsCrJQmV014v0llr +gDg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=vpL7JnOJtZBvWhUMx+VZwcGUuBH8cRMQzhoqZyElQAE=; b=0W63/Syzne718QZ0f8Qr+y8hQWUFhs+G4fVCYBfwJ7ElyWFng1Qr8ssCrev6UvKe+Q LPmvq2qLPs45P2CpbUDEmZP9/Md1fcXGX5jlF1zOtu7guxPyyUidK8M/pN3R30CKhOBv /JFyfsnIkYWbqlsMMB/R1khRFgd/sDwV7+oQYzIXFmGl4yvElYmxLJWHgIpepeV8OBml 4/pvKb18xNQ/pgTnfTYid2SZ27y+MayE2+dnt/5bIrdq5Lt7yisfVE0+5CO0+Ktn+MNJ eXjy2RC/i4c68mBhM/oQ51bNV61vOzhyGO336GJQT9S1O2kDqEotxl88IhB72kbn3UGS +bOQ== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.71.90 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , David Hildenbrand , Paolo Bonzini , Wanpeng Li , Sasha Levin Subject: [PATCH 4.9 36/86] KVM: X86: Fix softlockup when get the current kvmclock Date: Fri, 2 Feb 2018 17:57:56 +0100 Message-Id: <20180202140825.835561072@linuxfoundation.org> X-Mailer: git-send-email 2.16.1 In-Reply-To: <20180202140822.679101338@linuxfoundation.org> References: <20180202140822.679101338@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1591309559973496793?= X-GMAIL-MSGID: =?utf-8?q?1591309559973496793?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wanpeng Li [ Upstream commit e70b57a6ce4e8b92a56a615ae79bdb2bd66035e7 ] 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_time_ref_counter+0x5a/0x80 [kvm] kvm_hv_process_stimers+0x120/0x5f0 [kvm] kvm_arch_vcpu_ioctl_run+0x4b4/0x1690 [kvm] kvm_vcpu_ioctl+0x33a/0x620 [kvm] do_vfs_ioctl+0xa1/0x5d0 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. Reviewed-by: Radim Krčmář Reviewed-by: David Hildenbrand Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1751,10 +1751,13 @@ static u64 __get_kvmclock_ns(struct 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();