KVM: x86/mmu: Make Host-writable and MMU-writable bit locations dynamic

Make the location of the HOST_WRITABLE and MMU_WRITABLE configurable for
a given KVM instance.  This will allow EPT to use high available bits,
which in turn will free up bit 11 for a constant MMU_PRESENT bit.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210225204749.1512652-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 63bf9aa5aefa..67e8c7c7a6ce 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -129,7 +129,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
  * 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 SPTE_MMU_WRITEABLE bit.
+ * 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
@@ -140,17 +140,17 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
  * 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 SPTE_MMU_WRITEABLE bit
- * is set, it works since another case never touches SPTE_MMU_WRITEABLE bit.
+ * 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 SPTE_MMU_WRITEABLE becomes
+ * 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 SPTE_MMU_WRITEABLE and PT_WRITABLE_MASK:
+ * 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 SPTE_MMU_WRITEABLE, this is the most
+ *   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.