KVM: x86/mmu: Don't drop level/direct from MMU role calculation

Use the calculated role as-is when propagating it to kvm_mmu.mmu_role,
i.e. stop masking off meaningful fields.  The concept of masking off
fields came from kvm_mmu_pte_write(), which (correctly) ignores certain
fields when comparing kvm_mmu_page.role against kvm_mmu.mmu_role, e.g.
the current mmu's access and level have no relation to a shadow page's
access and level.

Masking off the level causes problems for 5-level paging, e.g. CR4.LA57
has its own redundant flag in the extended role, and nested EPT would
need a similar hack to support 5-level paging for L2.

Opportunistically rework the mask for kvm_mmu_pte_write() to define the
fields that should be ignored as opposed to the fields that should be
checked, i.e. make it opt-out instead of opt-in so that new fields are
automatically picked up.  While doing so, stop ignoring "direct".  The
field is effectively ignored anyways because kvm_mmu_pte_write() is only
reached with an indirect mmu and the loop only walks indirect shadow
pages, but double checking "direct" literally costs nothing.

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/mmu.c b/arch/x86/kvm/mmu/mmu.c
index db0b66e153a2d5af5c97b7a43fd44b5b91f0db53..8b22fc0f0973a9a224a94f5ba4e0b0fac9c82dee 100644 (file)
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -215,17 +215,6 @@ struct kvm_shadow_walk_iterator {
        unsigned index;
 };
 
-static const union kvm_mmu_page_role mmu_base_role_mask = {
-       .cr0_wp = 1,
-       .gpte_is_8_bytes = 1,
-       .nxe = 1,
-       .smep_andnot_wp = 1,
-       .smap_andnot_wp = 1,
-       .smm = 1,
-       .guest_mode = 1,
-       .ad_disabled = 1,
-};
-
 #define for_each_shadow_entry_using_root(_vcpu, _root, _addr, _walker)     \
        for (shadow_walk_init_using_root(&(_walker), (_vcpu),              \
                                         (_root), (_addr));                \
@@ -4930,7 +4919,6 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
        union kvm_mmu_role new_role =
                kvm_calc_tdp_mmu_root_page_role(vcpu, false);
 
-       new_role.base.word &= mmu_base_role_mask.word;
        if (new_role.as_u64 == context->mmu_role.as_u64)
                return;
 
@@ -5002,7 +4990,6 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu)
        union kvm_mmu_role new_role =
                kvm_calc_shadow_mmu_root_page_role(vcpu, false);
 
-       new_role.base.word &= mmu_base_role_mask.word;
        if (new_role.as_u64 == context->mmu_role.as_u64)
                return;
 
@@ -5059,7 +5046,6 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
 
        __kvm_mmu_new_cr3(vcpu, new_eptp, new_role.base, false);
 
-       new_role.base.word &= mmu_base_role_mask.word;
        if (new_role.as_u64 == context->mmu_role.as_u64)
                return;
 
@@ -5100,7 +5086,6 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
        union kvm_mmu_role new_role = kvm_calc_mmu_role_common(vcpu, false);
        struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;
 
-       new_role.base.word &= mmu_base_role_mask.word;
        if (new_role.as_u64 == g_context->mmu_role.as_u64)
                return;
 
@@ -5339,6 +5324,22 @@ static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
        return spte;
 }
 
+/*
+ * Ignore various flags when determining if a SPTE can be immediately
+ * overwritten for the current MMU.
+ *  - level: explicitly checked in mmu_pte_write_new_pte(), and will never
+ *    match the current MMU role, as MMU's level tracks the root level.
+ *  - access: updated based on the new guest PTE
+ *  - quadrant: handled by get_written_sptes()
+ *  - invalid: always false (loop only walks valid shadow pages)
+ */
+static const union kvm_mmu_page_role role_ign = {
+       .level = 0xf,
+       .access = 0x7,
+       .quadrant = 0x3,
+       .invalid = 0x1,
+};
+
 static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                              const u8 *new, int bytes,
                              struct kvm_page_track_notifier_node *node)
@@ -5394,8 +5395,8 @@ static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                        entry = *spte;
                        mmu_page_zap_pte(vcpu->kvm, sp, spte);
                        if (gentry &&
-                             !((sp->role.word ^ base_role)
-                             & mmu_base_role_mask.word) && rmap_can_add(vcpu))
+                           !((sp->role.word ^ base_role) & ~role_ign.word) &&
+                           rmap_can_add(vcpu))
                                mmu_pte_write_new_pte(vcpu, sp, spte, &gentry);
                        if (need_remote_flush(entry, *spte))
                                remote_flush = true;