Re: [Xen-devel] [PATCH v1 1/2] x86/mm: Add mem access rights to NPT

[Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>]

On Mi, 2018-05-30 at 03:52 -0600, Jan Beulich wrote:
> >
> > >
> > > >
> > > > On 30.05.18 at 11:04, <aisaila@xxxxxxxxxxxxxxx> wrote:
> > Sorry for the misunderstanding, I wanted to clarify if the 59:56
> > bits
> > are fully ok to be used or if not then where should I use 4 bits to
> > store the mem access info?
> I thought I had sufficiently explained this - you have two options:
> 1) Make sure (via some prereq patch(es)) bit 59 has no other use, and
>    then use 59:56.
> 2) Use another range that's provably having no other use, e.g.
>    58:55.
I've checked and bits 40:52 are defined in asm/page.h for page flags.
I've tried bits 53:56 and there where some problems with the guest not
starting or the image freezing, bits 62 and 63 are not free so 59:56 is
the only space to be used for this purpose and is seems to function
correctly. Is there any test I should run?

Thanks,
Alex


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