Re: [Xen-devel] update_runstate_area and Linux KPTI

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/03/18 16:18, Jan Beulich wrote:
>>>> On 02.03.18 at 17:04, <andrew.cooper3@xxxxxxxxxx> wrote:
>> The proper way to do this is indeed by a nominated (guest) physical
>> address, at which point Xen can make all/any updates at times of its
>> choosing, and the guests pagetable/permissions state at an instantaneous
>> moment don't matter.
>>
>> If you've got time to do this, then please do.  It will be a definite
>> improvement.
> Just to be avoid unnecessary effort in the wrong direction: I don't
> think you can alter the current interface. You'd have to add a new
> one, and we could then deprecate (but never abandon) the current
> one.

No - we sadly can't remove the current interface (at least for a long
while), but we can immediately deprecate it when a better alternative is
available.

OTOH, I think it would be a very good idea to have a Kconfig option so
we can selectively excise legacy interfaces.  I expect this will be of
particular interest to embedded/bespoke configurations.

~Andrew

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