Re: "KVM: x86/mmu: Overhaul TDP MMU zapping and flushing" breaks SVM on Hyper-V

[Paolo Bonzini]

On 2/13/23 13:44, Jeremi Piotrowski wrote:
> Just built a kernel from that tree, and it displays the same behavior. The problem
> is not that the addresses are wrong, but that the flushes are issued at the wrong
> time now. At least for what "enlightened NPT TLB flush" requires.

It is not clear to me why HvCallFluyshGuestPhysicalAddressSpace or 
HvCallFlushGuestPhysicalAddressList would have stricter requirements 
than a "regular" TLB shootdown using INVEPT.

Can you clarify what you mean by wrong time, preferrably with some kind 
of sequence of events?

That is, something like

CPU 0	Modify EPT from ... to ...
CPU 0	call_rcu() to free page table
CPU 1	... which is invalid because ...
CPU 0	HvCallFlushGuestPhysicalAddressSpace

Paolo