linux-kernel - Re: [PATCH 1/3] KVM: x86: assign two bits to track SPTE kinds

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Date:   Thu, 26 Sep 2019 19:39:02 -0700
From:   Junaid Shahid <junaids@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH 1/3] KVM: x86: assign two bits to track SPTE kinds


On 9/26/19 10:18 AM, Paolo Bonzini wrote:
> Currently, we are overloading SPTE_SPECIAL_MASK to mean both
> "A/D bits unavailable" and MMIO, where the difference between the
> two is determined by mio_mask and mmio_value.
> 
> However, the next patch will need two bits to distinguish
> availability of A/D bits from write protection.  So, while at
> it give MMIO its own bit pattern, and move the two bits from
> bit 62 to bits 52..53 since Intel is allocating EPT page table
> bits from the top.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---

Reviewed-by: Junaid Shahid <junaids@...gle.com>