[SVM] Adding page access bits

[SVM] Adding page access bits

[Alexandru Stefan ISAILA]

Hello,

We want to add the page access functionality to the SVM code. We have
been trying to add 4 bits in the pte but all seem to be taken.

Is there a way to accommodate them in the 24 bit flag mask?

I think it can be done by moving the 4 protection key field bits from
22:19 to 23:30 so we can have the 19:16 for access. Not sure if bit 23
is clear

Any thoughts on this matter are appreciated.

Thanks,
Alex

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Re: [SVM] Adding page access bits

[Andrew Cooper]

On 10/05/18 13:59, Alexandru Stefan ISAILA wrote:
> Hello,
>
> We want to add the page access functionality to the SVM code. We have
> been trying to add 4 bits in the pte but all seem to be taken.
>
> Is there a way to accommodate them in the 24 bit flag mask?
>
> I think it can be done by moving the 4 protection key field bits from
> 22:19 to 23:30 so we can have the 19:16 for access. Not sure if bit 23
> is clear
>
> Any thoughts on this matter are appreciated.

The 4 protection key bits bits are architecturally defined.  You cannot
move the bits, or you will break Intel.

That said, I presume you mean the PTEs for the NPT pagetables?

AMD hardware doesn't support PKU yet, and if they were to implement
support, I doubt it would be implemented for the NPT tables.  Therefore,
I think you can just alias the 4 bits.

~Andrew

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