linux-kernel - Re: [PATCH v3 3/4] KVM: x86: Tie Intel and AMD behavior for MSR_TSC

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Message-ID: <YIiJAjZQevp+DT9h@google.com>
Date:   Tue, 27 Apr 2021 21:58:26 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Reiji Watanabe <reijiw@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] KVM: x86: Tie Intel and AMD behavior for
 MSR_TSC_AUX to guest CPU model

On Mon, Apr 26, 2021, Reiji Watanabe wrote:
 
> > There is also a kernel bug lurking; vgetcpu_cpu_init() doesn't check
> > X86_FEATURE_RDPID and will fail to initialize MSR_TSC_AUX if RDPID is supported
> > but RDTSCP is not, and __getcpu() uses RDPID.  I'll verify that's broken and
> > send a patch for that one too.
> 
> I don't find vgetcpu_cpu_init() or __getcpu() in
> https://github.com/torvalds/linux.
> I would assume you meant setup_getcpu() and vdso_read_cpunode() instead (?).

Ya, I was looking at an old kernel when I typed that up.  Bug is still there
though :-)