linux-kernel - Re: [PATCH v2] KVM: x86: use CPUID to locate host page table reserved bits

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Message-ID: <c1012d42-6e60-66c9-80ea-f6c26db37172@redhat.com>
Date:   Tue, 10 Dec 2019 10:18:51 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Cc:     "Christopherson, Sean J" <sean.j.christopherson@...el.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2] KVM: x86: use CPUID to locate host page table reserved
 bits

On 10/12/19 04:53, Huang, Kai wrote:
> Right. Alghouth both MKTME and SME/SEV reduce physical bits, but they treat
> those reduced bits differently: MKTME treats those as keyID thus they can be
> set, but SME/SEV treats those as reserved bits so you cannot set any of them.
> 
> Maybe the naming of shadow_phys_bits is a little bit confusing here. The purpose
> of it was to determine first reserved bits, but not actual physical address bits
> . Therefore for MKTME it should include the keyID bits, but for SME/SEV it
> should not.

Not just the first reserved bit, but _some_ reserved bit such that all
consecutive bits up to bit 51 are reserved.

Paolo