Re: [PATCH v3 17/17] KVM: x86/tdp_mmu: Take root types for kvm_tdp_mmu_invalidate_all_roots()

[Edgecombe, Rick P]

On Thu, 2024-07-18 at 08:28 -0700, Isaku Yamahata wrote:
> Although it's a bit late, it's for record.
> 
> It's to optimize the destruction Secure-EPT.  Free HKID early and destruct
> Secure-EPT by TDH.PHYMEM.PAGE.RECLAIM().  QEMU doesn't close any KVM file
> descriptors on exit. (gmem fd references KVM VM fd. so vm destruction happens
> after all gmem fds are closed.  Closing gmem fd causes secure-EPT zapping
> befure
> releasing HKID.)
> 
> Because we're ignoring such optimization for now, we can simply defer
> releasing
> HKID following Seans's call.

Thanks for the background.

> 
> 
> > But static_call_cond(kvm_x86_vm_destroy) happens before kvm_destroy_vcpus,
> > so we
> > could maybe actually just do the tdx_mmu_release_hkid() part there. Then
> > drop
> > the flush_shadow_all_private x86 op. See the (not thoroughly checked) diff
> > at
> > the bottom of this mail.
> 
> Yep, we can release HKID at vm destruction with potential too slow zapping of
> Secure-EPT.  The following change basically looks good to me.
> (The callback for Secure-EPT can be simplified.)