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 14:37:37 -0700 [thread overview]
Message-ID: <9b19f440-ee78-4a4f-ab87-e9fff26ea6a4@intel.com> (raw)
In-Reply-To: <8a34f1d4-9f43-4fa7-9566-144b5eeda4d9@intel.com>
(a short update ...)
On 7/3/24 1:14 PM, Reinette Chatre wrote:
> 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.
I have now been able to test on SKX also and I am not yet able to reproduce. For
reference, the systems I tested on are:
SKX: https://ark.intel.com/content/www/us/en/ark/products/120507/intel-xeon-platinum-8170m-processor-35-75m-cache-2-10-ghz.html
ICX: https://ark.intel.com/content/www/us/en/ark/products/212459/intel-xeon-platinum-8360y-processor-54m-cache-2-40-ghz.html
CLX: https://ark.intel.com/content/www/us/en/ark/products/192476/intel-xeon-platinum-8260l-processor-35-75m-cache-2-40-ghz.html
Reinette
next prev parent reply other threads:[~2024-07-03 21:38 UTC|newest]
Thread overview: 13+ 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
2024-07-03 21:37 ` Reinette Chatre [this message]
2024-07-08 5:55 ` Yuan Yao
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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