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Re: [PATCH 6/6] x86/hvm: Support PKS
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 21 Dec 2021 13:18:44 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 21 Dec 2021 12:19:04 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16.12.2021 10:54, Andrew Cooper wrote:
> With all infrastructure in place, advertise the PKS CPUID bit to guests, and
> let them set CR4.PKS.
>
> Experiment with a tweak to the layout of hvm_cr4_guest_valid_bits() so future
> additions will be just a single added line.
>
> The current context switching behaviour is tied to how VT-x works, so leave a
> safety check in the short term.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
I would like to ask though that you ...
> --- a/xen/include/public/arch-x86/cpufeatureset.h
> +++ b/xen/include/public/arch-x86/cpufeatureset.h
> @@ -244,7 +244,7 @@ XEN_CPUFEATURE(CLDEMOTE, 6*32+25) /*A CLDEMOTE
> instruction */
> XEN_CPUFEATURE(MOVDIRI, 6*32+27) /*a MOVDIRI instruction */
> XEN_CPUFEATURE(MOVDIR64B, 6*32+28) /*a MOVDIR64B instruction */
> XEN_CPUFEATURE(ENQCMD, 6*32+29) /* ENQCMD{,S} instructions */
> -XEN_CPUFEATURE(PKS, 6*32+31) /* Protection Key for Supervisor */
> +XEN_CPUFEATURE(PKS, 6*32+31) /*H Protection Key for Supervisor */
... clarify this restriction of not covering shadow mode guests by
an adjustment to title or description. Aiui the sole reason for
the restriction is that shadow code doesn't propagate the key bits
from guest to shadow PTEs?
Jan
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