kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A …

…bits.

This change implements lockless access tracking for Intel CPUs without EPT
A bits. This is achieved by marking the PTEs as not-present (but not
completely clearing them) when clear_flush_young() is called after marking
the pages as accessed. When an EPT Violation is generated as a result of
the VM accessing those pages, the PTEs are restored to their original values.

Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1064,7 +1064,8 @@ void kvm_mmu_setup(struct kvm_vcpu *vcpu);
 void kvm_mmu_init_vm(struct kvm *kvm);
 void kvm_mmu_uninit_vm(struct kvm *kvm);
 void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
-		u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask);
+		u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask,
+		u64 acc_track_mask);
 
 void kvm_mmu_reset_context(struct kvm_vcpu *vcpu);
 void kvm_mmu_slot_remove_write_access(struct kvm *kvm,

arch/x86/include/asm/vmx.h

@@ -469,11 +469,14 @@ enum vmcs_field {
 #define VMX_EPT_IPAT_BIT    			(1ull << 6)
 #define VMX_EPT_ACCESS_BIT			(1ull << 8)
 #define VMX_EPT_DIRTY_BIT			(1ull << 9)
+#define VMX_EPT_RWX_MASK                        (VMX_EPT_READABLE_MASK |       \
+						 VMX_EPT_WRITABLE_MASK |       \
+						 VMX_EPT_EXECUTABLE_MASK)
+#define VMX_EPT_MT_MASK				(7ull << VMX_EPT_MT_EPTE_SHIFT)
 
 /* The mask to use to trigger an EPT Misconfiguration in order to track MMIO */
-#define VMX_EPT_MISCONFIG_WX_VALUE           (VMX_EPT_WRITABLE_MASK |       \
-                                              VMX_EPT_EXECUTABLE_MASK)
-
+#define VMX_EPT_MISCONFIG_WX_VALUE		(VMX_EPT_WRITABLE_MASK |       \
+						 VMX_EPT_EXECUTABLE_MASK)
 
 #define VMX_EPT_IDENTITY_PAGETABLE_ADDR		0xfffbc000ul