KVM: x86: fix handling of role.cr4_pae and rename it to 'gpte_size'
The cr4_pae flag is a bit of a misnomer, its purpose is really to track
whether the guest PTE that is being shadowed is a 4-byte entry or an
8-byte entry. Prior to supporting nested EPT, the size of the gpte was
reflected purely by CR4.PAE. KVM fudged things a bit for direct sptes,
but it was mostly harmless since the size of the gpte never mattered.
Now that a spte may be tracking an indirect EPT entry, relying on
CR4.PAE is wrong and ill-named.
For direct shadow pages, force the gpte_size to '1' as they are always
8-byte entries; EPT entries can only be 8-bytes and KVM always uses
8-byte entries for NPT and its identity map (when running with EPT but
not unrestricted guest).
Likewise, nested EPT entries are always 8-bytes. Nested EPT presents a
unique scenario as the size of the entries are not dictated by CR4.PAE,
but neither is the shadow page a direct map. To handle this scenario,
set cr0_wp=1 and smap_andnot_wp=1, an otherwise impossible combination,
to denote a nested EPT shadow page. Use the information to avoid
incorrectly zapping an unsync'd indirect page in __kvm_sync_page().
Providing a consistent and accurate gpte_size fixes a bug reported by
Vitaly where fast_cr3_switch() always fails when switching from L2 to
L1 as kvm_mmu_get_page() would force role.cr4_pae=0 for direct pages,
whereas kvm_calc_mmu_role_common() would set it according to CR4.PAE.
Fixes: 7dcd575520082 ("x86/kvm/mmu: check if tdp/shadow MMU reconfiguration is needed")
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
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.c b/arch/x86/kvm/mmu.c
index 01bb090..776a58b0 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -182,7 +182,7 @@ struct kvm_shadow_walk_iterator {
static const union kvm_mmu_page_role mmu_base_role_mask = {
.cr0_wp = 1,
- .cr4_pae = 1,
+ .gpte_is_8_bytes = 1,
.nxe = 1,
.smep_andnot_wp = 1,
.smap_andnot_wp = 1,
@@ -2205,6 +2205,7 @@ static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
static void kvm_mmu_commit_zap_page(struct kvm *kvm,
struct list_head *invalid_list);
+
#define for_each_valid_sp(_kvm, _sp, _gfn) \
hlist_for_each_entry(_sp, \
&(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \
@@ -2215,12 +2216,17 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
for_each_valid_sp(_kvm, _sp, _gfn) \
if ((_sp)->gfn != (_gfn) || (_sp)->role.direct) {} else
+static inline bool is_ept_sp(struct kvm_mmu_page *sp)
+{
+ return sp->role.cr0_wp && sp->role.smap_andnot_wp;
+}
+
/* @sp->gfn should be write-protected at the call site */
static bool __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
struct list_head *invalid_list)
{
- if (sp->role.cr4_pae != !!is_pae(vcpu)
- || vcpu->arch.mmu->sync_page(vcpu, sp) == 0) {
+ if ((!is_ept_sp(sp) && sp->role.gpte_is_8_bytes != !!is_pae(vcpu)) ||
+ vcpu->arch.mmu->sync_page(vcpu, sp) == 0) {
kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);
return false;
}
@@ -2423,7 +2429,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
role.level = level;
role.direct = direct;
if (role.direct)
- role.cr4_pae = 0;
+ role.gpte_is_8_bytes = true;
role.access = access;
if (!vcpu->arch.mmu->direct_map
&& vcpu->arch.mmu->root_level <= PT32_ROOT_LEVEL) {
@@ -4794,7 +4800,6 @@ static union kvm_mmu_role kvm_calc_mmu_role_common(struct kvm_vcpu *vcpu,
role.base.access = ACC_ALL;
role.base.nxe = !!is_nx(vcpu);
- role.base.cr4_pae = !!is_pae(vcpu);
role.base.cr0_wp = is_write_protection(vcpu);
role.base.smm = is_smm(vcpu);
role.base.guest_mode = is_guest_mode(vcpu);
@@ -4815,6 +4820,7 @@ kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only)
role.base.ad_disabled = (shadow_accessed_mask == 0);
role.base.level = kvm_x86_ops->get_tdp_level(vcpu);
role.base.direct = true;
+ role.base.gpte_is_8_bytes = true;
return role;
}
@@ -4879,6 +4885,7 @@ kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu, bool base_only)
role.base.smap_andnot_wp = role.ext.cr4_smap &&
!is_write_protection(vcpu);
role.base.direct = !is_paging(vcpu);
+ role.base.gpte_is_8_bytes = !!is_pae(vcpu);
if (!is_long_mode(vcpu))
role.base.level = PT32E_ROOT_LEVEL;
@@ -4919,21 +4926,24 @@ kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
bool execonly)
{
union kvm_mmu_role role = {0};
- union kvm_mmu_page_role root_base = vcpu->arch.root_mmu.mmu_role.base;
- /* Legacy paging and SMM flags are inherited from root_mmu */
- role.base.smm = root_base.smm;
- role.base.nxe = root_base.nxe;
- role.base.cr0_wp = root_base.cr0_wp;
- role.base.smep_andnot_wp = root_base.smep_andnot_wp;
- role.base.smap_andnot_wp = root_base.smap_andnot_wp;
+ /* SMM flag is inherited from root_mmu */
+ role.base.smm = vcpu->arch.root_mmu.mmu_role.base.smm;
role.base.level = PT64_ROOT_4LEVEL;
+ role.base.gpte_is_8_bytes = true;
role.base.direct = false;
role.base.ad_disabled = !accessed_dirty;
role.base.guest_mode = true;
role.base.access = ACC_ALL;
+ /*
+ * WP=1 and NOT_WP=1 is an impossible combination, use WP and the
+ * SMAP variation to denote shadow EPT entries.
+ */
+ role.base.cr0_wp = true;
+ role.base.smap_andnot_wp = true;
+
role.ext = kvm_calc_mmu_role_ext(vcpu);
role.ext.execonly = execonly;
@@ -5184,7 +5194,7 @@ static bool detect_write_misaligned(struct kvm_mmu_page *sp, gpa_t gpa,
gpa, bytes, sp->role.word);
offset = offset_in_page(gpa);
- pte_size = sp->role.cr4_pae ? 8 : 4;
+ pte_size = sp->role.gpte_is_8_bytes ? 8 : 4;
/*
* Sometimes, the OS only writes the last one bytes to update status
@@ -5208,7 +5218,7 @@ static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
page_offset = offset_in_page(gpa);
level = sp->role.level;
*nspte = 1;
- if (!sp->role.cr4_pae) {
+ if (!sp->role.gpte_is_8_bytes) {
page_offset <<= 1; /* 32->64 */
/*
* A 32-bit pde maps 4MB while the shadow pdes map