KVM: x86/mmu: Incorporate guest's page level into max level for shadow MMU

Restrict the max level for a shadow page based on the guest's level
instead of capping the level after the fact for host-mapped huge pages,
e.g. hugetlbfs pages.  Explicitly capping the max level using the guest
mapping level also eliminates FNAME(page_fault)'s subtle dependency on
THP only supporting 2mb pages.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 1938a6e4e631012234b961cd2da998a9f76829fb..7d57ec576df0c8913b4c45e16312b64323265e1a 100644 (file)
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -773,7 +773,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
        struct guest_walker walker;
        int r;
        kvm_pfn_t pfn;
-       int level = PT_PAGE_TABLE_LEVEL;
+       int level;
        unsigned long mmu_seq;
        bool map_writable, is_self_change_mapping;
        bool lpage_disallowed = (error_code & PFERR_FETCH_MASK) &&
@@ -818,18 +818,14 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gpa_t addr, u32 error_code,
        is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu,
              &walker, user_fault, &vcpu->arch.write_fault_to_shadow_pgtable);
 
-       max_level = lpage_disallowed ? PT_PAGE_TABLE_LEVEL :
-                                      PT_MAX_HUGEPAGE_LEVEL;
-
-       if (walker.level >= PT_DIRECTORY_LEVEL && !is_self_change_mapping) {
-               level = mapping_level(vcpu, walker.gfn, &max_level);
-               if (likely(max_level > PT_DIRECTORY_LEVEL)) {
-                       level = min(walker.level, level);
-                       walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
-               }
-       } else {
+       if (lpage_disallowed || is_self_change_mapping)
                max_level = PT_PAGE_TABLE_LEVEL;
-       }
+       else
+               max_level = walker.level;
+
+       level = mapping_level(vcpu, walker.gfn, &max_level);
+       if (level > PT_PAGE_TABLE_LEVEL)
+               walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
 
        mmu_seq = vcpu->kvm->mmu_notifier_seq;
        smp_rmb();