KVM: x86/tdp_mmu: Take a GFN in kvm_tdp_mmu_fast_pf_get_last_sptep()

KVM: x86/tdp_mmu: Take a GFN in kvm_tdp_mmu_fast_pf_get_last_sptep()

Pass fault->gfn into kvm_tdp_mmu_fast_pf_get_last_sptep(), instead of
passing fault->addr and then converting it to a GFN.

Future changes will make fault->addr and fault->gfn differ when running
TDX guests. The GFN will be conceptually the same as it is for normal VMs,
but fault->addr may contain a TDX specific bit that differentiates between
"shared" and "private" memory. This bit will be used to direct faults to
be handled on different roots, either the normal "direct" root or a new
type of root that handles private memory. The TDP iterators will process
the traditional GFN concept and apply the required TDX specifics depending
on the root type. For this reason, it needs to operate on regular GFN and
not the addr, which may contain these special TDX specific bits.

Today kvm_tdp_mmu_fast_pf_get_last_sptep() takes fault->addr and then
immediately converts it to a GFN with a bit shift. However, this would
unfortunately retain the TDX specific bits in what is supposed to be a
traditional GFN. Excluding TDX's needs, it is also is unnecessary to pass
fault->addr and convert it to a GFN when the GFN is already on hand.

So instead just pass the GFN into kvm_tdp_mmu_fast_pf_get_last_sptep() and
use it directly.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <20240619223614.290657-9-rick.p.edgecombe@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>