Re: [Xen-devel] [PATCH] x86/HVM: Merge HVM and PVH hypercall tables

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.12.15 at 15:20, <boris.ostrovsky@xxxxxxxxxx> wrote:
> The tables are almost identical and therefore there is little reason to
> keep both sets.
> 
> PVH needs 3 extra hypercalls:
> * mmuext_op. PVH uses MMUEXT_TLB_FLUSH_MULTI and MMUEXT_INVLPG_MULTI to
>   optimize TLB flushing. Since HVMlite guests may decide to use them as
>   well we can allow these two commands for all guests in an HVM container.

I must be missing something here: Especially for the INVLPG variant
I can't see what use it could be for a PVH guest, as it necessarily
would act on a different address space (the other one may have at
least some effect due to hvm_flush_guest_tlbs()).

And then, if those two really are meant to be enabled, why would
their _LOCAL and _ALL counterparts not be? And similarly,
MMUEXT_FLUSH_CACHE{,_GLOBAL} may then be valid to expose.

Wasn't it much rather that PVH Dom0 needed e.g. MMUEXT_PIN_Ln_TABLE
to deal with foreign guests' page tables?

Jan


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