KVM: X86/MMU: Use one-off special shadow page for special roots

From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

Current code uses mmu->pae_root, mmu->pml4_root, and mmu->pml5_root to
setup special roots.  The initialization code is complex and the roots
are not associated with struct kvm_mmu_page which causes the code more
complex.

So add new special shadow pages to simplify it.

The special shadow pages are associated with struct kvm_mmu_page and
VCPU-local.

The special shadow pages are created and freed when the roots are
changed (or one-off) which can be optimized but not in the patchset
since the re-creating is light way (in normal case only the struct
kvm_mmu_page needs to be re-allocated and sp->spt doens't, because
it is likely to be mmu->pae_root)

Changed from v1:
	Rebase to newest kvm/queue. Slightly update patch4.

[V1]: https://lore.kernel.org/lkml/20220420132605.3813-1-jiangs...

Lai Jiangshan (7):
  KVM: X86/MMU: Add using_special_root_page()
  KVM: X86/MMU: Add special shadow pages
  KVM: X86/MMU: Link PAE root pagetable with its children
  KVM: X86/MMU: Activate special shadow pages and remove old logic
  KVM: X86/MMU: Remove the check of the return value of to_shadow_page()
  KVM: X86/MMU: Allocate mmu->pae_root for PAE paging on-demand
  KVM: X86/MMU: Remove mmu_alloc_special_roots()

 arch/x86/include/asm/kvm_host.h |   3 -
 arch/x86/kvm/mmu/mmu.c          | 487 ++++++++++----------------------
 arch/x86/kvm/mmu/mmu_internal.h |  10 -
 arch/x86/kvm/mmu/paging_tmpl.h  |  14 +-
 arch/x86/kvm/mmu/spte.c         |   7 +
 arch/x86/kvm/mmu/spte.h         |   1 +
 arch/x86/kvm/mmu/tdp_mmu.h      |   7 +-
 7 files changed, 178 insertions(+), 351 deletions(-)

-- 
2.19.1.6.gb485710b