Message-ID: <620e127f-59d3-ccad-e0f6-39ca9ee7098e@redhat.com>
Date:   Thu, 25 Nov 2021 21:17:47 +0100
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Subject: Re: [RFC PATCH v3 46/59] KVM: VMX: Move register caching logic to
 common code
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To:     Thomas Gleixner <tglx@linutronix.de>, isaku.yamahata@intel.com,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, erdemaktas@google.com,
        Connor Kuehl <ckuehl@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     isaku.yamahata@gmail.com,
        Sean Christopherson <sean.j.christopherson@intel.com>
References: <cover.1637799475.git.isaku.yamahata@intel.com>
 <2f3c1207f66f44fdd2f3eb0809d552f5632e4b41.1637799475.git.isaku.yamahata@intel.com>
 <87mtlshu66.ffs@tglx>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <87mtlshu66.ffs@tglx>
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On 11/25/21 21:11, Thomas Gleixner wrote:
>>
>> Use kvm_x86_ops.cache_reg() in ept_update_paging_mode_cr0() rather than
>> trying to expose vt_cache_reg() to vmx.c, even though it means taking a
>> retpoline.  The code runs if and only if EPT is enabled but unrestricted
>> guest.
> This sentence does not parse because it's not a proper sentence.
> 
>> Only one generation of CPU, Nehalem, supports EPT but not
>> unrestricted guest, and disabling unrestricted guest without also
>> disabling EPT is, to put it bluntly, dumb.
> This one is only significantly better and lacks an explanation what this
> means for the dumb case.

Well, it means a retpoline (see paragraph before).  However, I'm not 
sure why it one wouldn't create a vt.h header with all vt_* functions.

Paolo