KVM: x86/mmu: Remove the defunct update_pte() paging hook

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Remove the update_pte() shadow paging logic, which was obsoleted by
commit 4731d4c7a0 ("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>

...

This commit is contained in:

Sean Christopherson 2021-01-14 16:40:51 -08:00 • committed by Paolo Bonzini

parent 678e90a349

commit c5e2184d15

3 changed files with 2 additions and 51 deletions

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3

arch/x86/include/asm/kvm_host.h

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49

arch/x86/kvm/mmu/mmu.c

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1

arch/x86/kvm/x86.c

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