linux-kernel - Re: [RFC 25/33] KVM: Introduce a set of new memory attributes

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Message-ID: <075453e1-830e-43bc-8888-7e5e4888223f@amazon.com>
Date:   Wed, 8 Nov 2023 13:30:32 +0100
From:   Alexander Graf <graf@...zon.com>
To:     Nicolas Saenz Julienne <nsaenz@...zon.com>, <kvm@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-hyperv@...r.kernel.org>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <anelkz@...zon.com>, <dwmw@...zon.co.uk>, <jgowans@...zon.com>,
        <corbert@....net>, <kys@...rosoft.com>, <haiyangz@...rosoft.com>,
        <decui@...rosoft.com>, <x86@...nel.org>,
        <linux-doc@...r.kernel.org>
Subject: Re: [RFC 25/33] KVM: Introduce a set of new memory attributes


On 08.11.23 12:17, Nicolas Saenz Julienne wrote:
> Introduce the following memory attributes:
>   - KVM_MEMORY_ATTRIBUTE_READ
>   - KVM_MEMORY_ATTRIBUTE_WRITE
>   - KVM_MEMORY_ATTRIBUTE_EXECUTE
>   - KVM_MEMORY_ATTRIBUTE_NO_ACCESS
>
> Note that NO_ACCESS is necessary in order to make a distinction between
> the lack of attributes for a gfn, which defaults to the memory
> protections of the backing memory, versus explicitly prohibiting any
> access to that gfn.


If we negate the attributes (no read, no write, no execute), we can keep 
0 == default and 0b111 becomes "no access".


Alex




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