KVM: X86: Move PTE present check from loop body to __shadow_walk_next()

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So far, the loop bodies already ensure the PTE is present before calling
__shadow_walk_next():  Some loop bodies simply exit with a !PRESENT
directly and some other loop bodies, i.e. FNAME(fetch) and __direct_map()
do not currently guard their walks with is_shadow_present_pte, but only
because they install present non-leaf SPTEs in the loop itself.

But checking pte present in __shadow_walk_next() (which is called from
shadow_walk_okay()) is more prudent; walking past a !PRESENT SPTE
would lead to attempting to read a the next level SPTE from a garbage
iter->shadow_addr.  It also allows to remove the is_shadow_present_pte()
checks from the loop bodies.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20210906122547.263316-2-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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Lai Jiangshan 2021-09-06 20:25:47 +08:00 • committed by Paolo Bonzini

parent 5228eb96a4

commit 3e44dce4d0

2 changed files with 3 additions and 12 deletions

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13

arch/x86/kvm/mmu/mmu.c

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2

arch/x86/kvm/mmu/paging_tmpl.h

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