KVM: x86/mmu: Move is_writable_pte() to spte.h

Move is_writable_pte() close to the other functions that check
writability information about SPTEs. While here opportunistically
replace the open-coded bit arithmetic in
check_spte_writable_invariants() with a call to is_writable_pte().

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220125230518.1697048-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 0 insertions, 38 deletions

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index e9fbb2c8bbe2..51faa2c76ca5 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -203,44 +203,6 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 }
 
 /*
- * Currently, we have two sorts of write-protection, a) the first one
- * write-protects guest page to sync the guest modification, b) another one is
- * used to sync dirty bitmap when we do KVM_GET_DIRTY_LOG. The differences
- * between these two sorts are:
- * 1) the first case clears MMU-writable bit.
- * 2) the first case requires flushing tlb immediately avoiding corrupting
- *    shadow page table between all vcpus so it should be in the protection of
- *    mmu-lock. And the another case does not need to flush tlb until returning
- *    the dirty bitmap to userspace since it only write-protects the page
- *    logged in the bitmap, that means the page in the dirty bitmap is not
- *    missed, so it can flush tlb out of mmu-lock.
- *
- * So, there is the problem: the first case can meet the corrupted tlb caused
- * by another case which write-protects pages but without flush tlb
- * immediately. In order to making the first case be aware this problem we let
- * it flush tlb if we try to write-protect a spte whose MMU-writable bit
- * is set, it works since another case never touches MMU-writable bit.
- *
- * Anyway, whenever a spte is updated (only permission and status bits are
- * changed) we need to check whether the spte with MMU-writable becomes
- * readonly, if that happens, we need to flush tlb. Fortunately,
- * mmu_spte_update() has already handled it perfectly.
- *
- * The rules to use MMU-writable and PT_WRITABLE_MASK:
- * - if we want to see if it has writable tlb entry or if the spte can be
- *   writable on the mmu mapping, check MMU-writable, this is the most
- *   case, otherwise
- * - if we fix page fault on the spte or do write-protection by dirty logging,
- *   check PT_WRITABLE_MASK.
- *
- * TODO: introduce APIs to split these two cases.
- */
-static inline bool is_writable_pte(unsigned long pte)
-{
-	return pte & PT_WRITABLE_MASK;
-}
-
-/*
  * Check if a given access (described through the I/D, W/R and U/S bits of a
  * page fault error code pfec) causes a permission fault with the given PTE
  * access rights (in ACC_* format).