On 23/06/21 18:21, Sean Christopherson wrote:
On Wed, Jun 23, 2021, Sean Christopherson wrote:
And I believe this hackery is necessary only because nested_svm_vmexit() isn't
following the architcture in the first place. I.e. using vmcb01 to restore
host state is flat out wrong.
Ah, that's not true, using vmcb01 is allowed by "may store some or all host state
in hidden on-chip memory".
And also, "Different implementations may choose to save the hidden parts
of the host’s segment registers as well as the selectors".
From a performance perspective, I do like the SMI/RSM shenanigans. I'm not
totally opposed to the trickery since I think it will break a guest if and only
if the L1 guest is also violating the APM. And we're not fudging the spec thaat
much :-)
Yeah, that was my reasoning as well. Any reference to "hidden on-chip
memory", plus the forbidding modifications of the host save area, sort
of implies that the processor can actually flush that hidden on-chip
memory for whatever reason (such as on some sleep states?!?).
Paolo
