linux-kernel - Re: [PATCH v2 1/5] mmu: extend the is

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Message-ID: <50ec82ef-eab1-13e5-3956-302f07419fb0@redhat.com>
Date:   Thu, 1 Sep 2016 17:16:09 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Li, Liang Z" <liang.z.li@...el.com>, Bandan Das <bsd@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Cc:     "guangrong.xiao@...ux.intel.com" <guangrong.xiao@...ux.intel.com>,
        "kernellwp@...il.com" <kernellwp@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] mmu: extend the is_present check to 32 bits



On 01/09/2016 16:20, Li, Liang Z wrote:
> Intel SDM doesn't describe whether the A bit will be set or not when
> CPU accesses  a no present EPT page table entry

Bits in a non-present page table entry are entirely for use by the OS.
The processor will never touch it.  This includes both P=0 in non-EPT
page tables and XWR=000 in EPT page tables.

Paolo