linux-kernel - Re: [PATCH V4 0/4] KVM: x86: Make bus clock frequency for vAPIC timer configurable

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Message-ID: <Ziku9m_1hQhJgm_m@google.com>
Date: Wed, 24 Apr 2024 09:13:26 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Rick P Edgecombe <rick.p.edgecombe@...el.com>
Cc: "jmattson@...gle.com" <jmattson@...gle.com>, Chao Gao <chao.gao@...el.com>, 
	"vkuznets@...hat.com" <vkuznets@...hat.com>, Vishal Annapurve <vannapurve@...gle.com>, 
	Reinette Chatre <reinette.chatre@...el.com>, Xiaoyao Li <xiaoyao.li@...el.com>, 
	Erdem Aktas <erdemaktas@...gle.com>, "pbonzini@...hat.com" <pbonzini@...hat.com>, 
	"mlevitsk@...hat.com" <mlevitsk@...hat.com>, Isaku Yamahata <isaku.yamahata@...el.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4 0/4] KVM: x86: Make bus clock frequency for vAPIC timer configurable

On Tue, Apr 16, 2024, Rick P Edgecombe wrote:
> On Thu, 2024-03-21 at 09:37 -0700, Reinette Chatre wrote:
> > 
> > Summary
> > -------
> > Add KVM_CAP_X86_APIC_BUS_FREQUENCY capability to configure the APIC
> > bus clock frequency for APIC timer emulation.
> > Allow KVM_ENABLE_CAPABILITY(KVM_CAP_X86_APIC_BUS_FREQUENCY) to set the
> > frequency in nanoseconds. When using this capability, the user space
> > VMM should configure CPUID leaf 0x15 to advertise the frequency.
> 
> Looks good to me and...
> Tested-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> 
> The only thing missing is actually integrating it into TDX qemu patches and
> testing the resulting TD. I think we are making a fair assumption that the
> problem should be resolved based on the analysis, but we have not actually
> tested that part. Is that right?

Please tell me that Rick is wrong, and that this actually has been tested with
a TDX guest.  I don't care _who_ tested it, or with what VMM it has been tested,
but _someone_ needs to verify that this actually fixes the TDX issue.