From: Reinette Chatre <reinette.chatre@intel.com>
To: Sean Christopherson <seanjc@google.com>
Cc: <isaku.yamahata@intel.com>, <pbonzini@redhat.com>,
<erdemaktas@google.com>, <vkuznets@redhat.com>,
<vannapurve@google.com>, <jmattson@google.com>,
<mlevitsk@redhat.com>, <xiaoyao.li@intel.com>,
<chao.gao@intel.com>, <rick.p.edgecombe@intel.com>,
<yuan.yao@intel.com>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
"Hao, Xudong" <xudong.hao@intel.com>
Subject: Re: VMX Preemption Timer appears to be buggy on SKX, CLX, and ICX
Date: Wed, 3 Jul 2024 13:14:09 -0700 [thread overview]
Message-ID: <8a34f1d4-9f43-4fa7-9566-144b5eeda4d9@intel.com> (raw)
In-Reply-To: <Zn9X0yFxZi_Mrlnt@google.com>
Hi Sean,
On 6/28/24 5:39 PM, Sean Christopherson wrote:
> Forking this off to try and avoid confusion...
>
> On Wed, Jun 12, 2024, Reinette Chatre wrote:
...
>> +
>> + freq = (tmict - tmcct) * tdcrs[i].divide_count * tsc_hz / (tsc1 - tsc0);
>> + /* Check if measured frequency is within 1% of configured frequency. */
>> + GUEST_ASSERT(freq < apic_hz * 101 / 100);
>> + GUEST_ASSERT(freq > apic_hz * 99 / 100);
>> + }
>
> This test fails on our SKX, CLX, and ICX systems due to what appears to be a CPU
> bug. It looks like something APICv related is clobbering internal VMX timer state?
> Or maybe there's a tearing or truncation issue?
It has been a few days. Just a note to let you know that we are investigating this.
On my side I have not yet been able to reproduce this issue. I tested
kvm-x86-next-2024.06.28 on an ICX and an CLX system by running 100 iterations of
apic_bus_clock_test and they all passed. Since I have lack of experience here there are
some Intel virtualization experts helping out with this investigation and I hope that
they will be some insights from the analysis and testing that you already provided.
Reinette
next prev parent reply other threads:[~2024-07-03 20:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-12 18:16 [PATCH V9 0/2] KVM: x86: Make bus clock frequency for vAPIC timer configurable Reinette Chatre
2024-06-12 18:16 ` [PATCH V9 1/2] KVM: selftests: Add x86_64 guest udelay() utility Reinette Chatre
2024-06-28 22:46 ` Sean Christopherson
2024-06-12 18:16 ` [PATCH V9 2/2] KVM: selftests: Add test for configure of x86 APIC bus frequency Reinette Chatre
2024-06-28 22:50 ` Sean Christopherson
2024-06-29 0:39 ` VMX Preemption Timer appears to be buggy on SKX, CLX, and ICX Sean Christopherson
2024-07-03 20:14 ` Reinette Chatre [this message]
2024-07-03 21:37 ` Reinette Chatre
2024-07-08 5:55 ` Yuan Yao
2026-05-13 1:31 ` Chao Gao
2026-05-14 21:09 ` Sean Christopherson
2026-05-15 6:34 ` Chao Gao
2024-06-28 22:55 ` [PATCH V9 0/2] KVM: x86: Make bus clock frequency for vAPIC timer configurable Sean Christopherson
2024-06-29 0:10 ` Reinette Chatre
2024-07-10 15:42 ` Sean Christopherson
2024-07-10 17:14 ` Reinette Chatre
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