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KVM: x86/mmu: Remove the defunct update_pte() paging hook
commit c5e2184 upstream. Remove the update_pte() shadow paging logic, which was obsoleted by commit 4731d4c ("KVM: MMU: out of sync shadow core"), but never removed. As pointed out by Yu, KVM never write protects leaf page tables for the purposes of shadow paging, and instead marks their associated shadow page as unsync so that the guest can write PTEs at will. The update_pte() path, which predates the unsync logic, optimizes COW scenarios by refreshing leaf SPTEs when they are written, as opposed to zapping the SPTE, restarting the guest, and installing the new SPTE on the subsequent fault. Since KVM no longer write-protects leaf page tables, update_pte() is unreachable and can be dropped. Reported-by: Yu Zhang <yu.c.zhang@intel.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20210115004051.4099250-1-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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