Re: Runstate hypercall and Linux KPTI issues

[Jan Beulich <jbeulich@xxxxxxxx>]

On 10.09.2020 16:00, Bertrand Marquis wrote:
>> On 10 Sep 2020, at 14:56, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>> On 10.09.2020 15:46, Bertrand Marquis wrote:
>>> Some open questions:
>>> - should we allow to register an area using both hypercalls or should it be 
>>> exclusive ?
>>
>> I thought it was already clarified that to a certain degree both need
>> to remain usable at least in sequence, to allow transitioning control
>> between entirely independent entities (bootloader -> kernel -> dump-
>> kernel, for example).
> 
> Sorry my wording was not clear here
> 
> Should we allow to register 2 areas at the same time using both hypercalls 
> (one with
> virtual address and one with physical address) or should they be exclusive ie 
> one or
> the other but not both at the same time

Ah, okay. Just one area at a time, I would say.

>>> - should we backport the support for this hypercall in older kernel 
>>> releases ?
>>
>> It's a bug fix to KPTI, and as such ought to be at least eligible for
>> considering doing so?
> 
> That will mean also backport in Linux. What should be the scope ?

All longterm and stable trees which are affected, as I think is usual.

Jan