From: Sean Christopherson <seanjc@google.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Maxim Levitsky <mlevitsk@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Igor Mammedov <imammedo@redhat.com>,
kvm@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN
Date: Thu, 13 Jan 2022 16:26:21 +0000 [thread overview]
Message-ID: <YeBSrcNawgzvTzQ6@google.com> (raw)
In-Reply-To: <87wnj3n0k0.fsf@redhat.com>
On Thu, Jan 13, 2022, Vitaly Kuznetsov wrote:
> Maxim Levitsky <mlevitsk@redhat.com> writes:
> > For my nested AVIC work I would really want the APIC ID of a VCPU to be read-only
> > and be equal to vcpu_id.
> >
>
> Doesn't APIC ID have topology encoded in it?
Yeah, APIC IDs are derived from the topology. From the SDM (this doesn't
talk about core/SMT info, but that's included as well):
The hardware assigned APIC ID is based on system topology and includes encoding
for socket position and cluster information.
The SDM also says:
Some processors permit software to modify the APIC ID. However, the ability of
software to modify the APIC ID is processor model specific.
So I _think_ we could define KVM behavior to ignore writes from the _guest_, but
the APIC_ID == vcpu_id requirement won't fly as userspace expects to be able to
stuff virtual toplogy info into the APIC ID.
next prev parent reply other threads:[~2022-01-13 16:26 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-22 17:58 [PATCH 0/2] KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN Vitaly Kuznetsov
2021-11-22 17:58 ` [PATCH 1/2] KVM: selftests: Avoid KVM_SET_CPUID2 after KVM_RUN in hyperv_features test Vitaly Kuznetsov
2021-11-22 17:58 ` [PATCH 2/2] KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN Vitaly Kuznetsov
2021-11-26 12:20 ` Paolo Bonzini
2021-12-27 17:32 ` Igor Mammedov
2022-01-02 17:31 ` Paolo Bonzini
2022-01-03 8:04 ` Vitaly Kuznetsov
2022-01-03 9:40 ` Igor Mammedov
2022-01-03 12:56 ` Vitaly Kuznetsov
2022-01-05 8:17 ` Igor Mammedov
2022-01-05 9:12 ` Vitaly Kuznetsov
2022-01-05 9:10 ` Paolo Bonzini
2022-01-05 10:09 ` Vitaly Kuznetsov
2022-01-07 9:02 ` Vitaly Kuznetsov
2022-01-07 18:15 ` Paolo Bonzini
2022-01-11 8:00 ` Igor Mammedov
2022-01-12 13:58 ` Vitaly Kuznetsov
2022-01-12 18:39 ` Paolo Bonzini
2022-01-13 9:27 ` Vitaly Kuznetsov
2022-01-13 14:28 ` Maxim Levitsky
2022-01-13 14:36 ` Vitaly Kuznetsov
2022-01-13 14:41 ` Maxim Levitsky
2022-01-13 14:59 ` Vitaly Kuznetsov
2022-01-13 16:26 ` Sean Christopherson [this message]
2022-01-13 16:30 ` Maxim Levitsky
2022-01-13 22:33 ` Sean Christopherson
2022-01-14 8:28 ` Maxim Levitsky
2022-01-14 16:08 ` Sean Christopherson
2022-01-14 8:55 ` Igor Mammedov
2022-01-14 9:31 ` Vitaly Kuznetsov
2022-01-14 11:22 ` Igor Mammedov
2022-01-14 12:25 ` Vitaly Kuznetsov
2022-01-14 17:00 ` Sean Christopherson
2022-01-17 9:55 ` Vitaly Kuznetsov
2022-01-17 11:20 ` Paolo Bonzini
2022-01-17 13:02 ` Vitaly Kuznetsov
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