From: Thomas Gleixner <tglx@linutronix.de>
To: Zelin Deng <zelin.deng@linux.alibaba.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Wanpeng Li <wanpengli@tencent.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] Guest system time jumps when new vCPUs is hot-added
Date: Wed, 28 Apr 2021 11:00:18 +0200 [thread overview]
Message-ID: <87lf92n5r1.ffs@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1619576521-81399-1-git-send-email-zelin.deng@linux.alibaba.com>
On Wed, Apr 28 2021 at 10:22, Zelin Deng wrote:
> Hello,
> I have below VM configuration:
> ...
> <vcpu placement='static' current='1'>2</vcpu>
> <cpu mode='host-passthrough'>
> </cpu>
> <clock offset='utc'>
> <timer name='tsc' frequency='3000000000'/>
> </clock>
> ...
> After VM has been up for a few minutes, I use "virsh setvcpus" to hot-add
> second vCPU into VM, below dmesg is observed:
> [ 53.273484] CPU1 has been hot-added
> [ 85.067135] SMP alternatives: switching to SMP code
> [ 85.078409] x86: Booting SMP configuration:
> [ 85.079027] smpboot: Booting Node 0 Processor 1 APIC 0x1
> [ 85.080240] kvm-clock: cpu 1, msr 77601041, secondary cpu clock
> [ 85.080450] smpboot: CPU 1 Converting physical 0 to logical die 1
> [ 85.101228] TSC ADJUST compensate: CPU1 observed 169175101528 warp. Adjust: 169175101528
> [ 141.513496] TSC ADJUST compensate: CPU1 observed 166 warp. Adjust: 169175101694
Why is TSC_ADJUST on CPU1 different from CPU0 in the first place?
That's broken.
Thanks,
tglx
next prev parent reply other threads:[~2021-04-28 9:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-28 2:22 [PATCH] Guest system time jumps when new vCPUs is hot-added Zelin Deng
2021-04-28 2:22 ` [PATCH] KVM: x86: Update vCPU's hv_clock before back to guest when tsc_offset is adjusted Zelin Deng
2021-04-28 9:00 ` Thomas Gleixner [this message]
2021-04-28 9:09 ` [PATCH] Guest system time jumps when new vCPUs is hot-added Thomas Gleixner
2021-04-28 23:24 ` Zelin Deng
2021-04-29 8:46 ` Thomas Gleixner
2021-04-29 9:38 ` Zelin Deng
2021-04-29 16:02 ` Thomas Gleixner
2021-04-29 22:40 ` Zelin Deng
2021-09-06 11:22 ` Paolo Bonzini
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