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Date:   Wed, 26 Feb 2020 13:25:37 -0800
From:   Sean Christopherson <sean.j.christopherson@intel.com>
To:     Jacob Keller <jacob.e.keller@intel.com>
Cc:     TonyWWang-oc@zhaoxin.com, acme@kernel.org,
        alexander.shishkin@linux.intel.com, bp@alien8.de, bp@suse.de,
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        lenb@kernel.org, linux-edac@vger.kernel.org,
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        tony.luck@intel.com, vkuznets@redhat.com, wanpengli@tencent.com,
        x86@kernel.org
Subject: Re: [PATCH v5 13/19] x86/cpufeatures: Add flag to track whether MSR
 IA32_FEAT_CTL is configured
Message-ID: <20200226212537.GR9940@linux.intel.com>
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On Wed, Feb 26, 2020 at 01:03:01PM -0800, Jacob Keller wrote:
> On 2/26/2020 12:57 PM, Sean Christopherson wrote:
> > Bummer.  Using clear_cpu_cap() instead of setup_clear_cpu_cap() was me
> > being fancy and trying to allow KVM to identify the case where VMX is
> > available and configured on some CPUs but not all.  I'll work on a fix.
> > 
> Hmm. Right. For that to work, you'd need to make this disabling happen
> significantly later, and/or fix setup_pku to somehow honor this properly.

Arguably, setup_pku() should be a little less heavy handed in updating
cpufeatures for X86_FEATURE_OSPKE, but init_ia32_feat_ctl() should also be
more robust.

I've reproduced the bug, should have a fix ready by EOD.

> But it looks like rdmsr is global and not tied to a given CPU anyways?

For better or worse, the MSR is thread scoped.