[PATCH] KVM: x86: simplify is_mmio_spte

[PATCH] KVM: x86: simplify is_mmio_spte

[Paolo Bonzini]

We can simply look at bits 52-53 to identify MMIO entries in KVM's page
tables.  Therefore, there is no need to pass a mask to kvm_mmu_set_mmio_spte_mask.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/mmu.h     |  2 +-
 arch/x86/kvm/mmu/mmu.c | 10 +++-------
 arch/x86/kvm/svm/svm.c |  2 +-
 arch/x86/kvm/vmx/vmx.c |  3 +--
 4 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 8a3b1bce722a..048e865ad485 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -51,7 +51,7 @@ static inline u64 rsvd_bits(int s, int e)
 	return ((1ULL << (e - s + 1)) - 1) << s;
 }
 
-void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask, u64 mmio_value, u64 access_mask);
+void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 access_mask);
 
 void
 reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 92d056954194..bef05a437a89 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -244,7 +244,6 @@ static u64 __read_mostly shadow_x_mask;	/* mutual exclusive with nx_mask */
 static u64 __read_mostly shadow_user_mask;
 static u64 __read_mostly shadow_accessed_mask;
 static u64 __read_mostly shadow_dirty_mask;
-static u64 __read_mostly shadow_mmio_mask;
 static u64 __read_mostly shadow_mmio_value;
 static u64 __read_mostly shadow_mmio_access_mask;
 static u64 __read_mostly shadow_present_mask;
@@ -331,21 +330,19 @@ static void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
 	kvm_flush_remote_tlbs_with_range(kvm, &range);
 }
 
-void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask, u64 mmio_value, u64 access_mask)
+void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 access_mask)
 {
 	BUG_ON((u64)(unsigned)access_mask != access_mask);
-	BUG_ON((mmio_mask & mmio_value) != mmio_value);
 	WARN_ON(mmio_value & (shadow_nonpresent_or_rsvd_mask << shadow_nonpresent_or_rsvd_mask_len));
 	WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask);
 	shadow_mmio_value = mmio_value | SPTE_MMIO_MASK;
-	shadow_mmio_mask = mmio_mask | SPTE_SPECIAL_MASK;
 	shadow_mmio_access_mask = access_mask;
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
 
 static bool is_mmio_spte(u64 spte)
 {
-	return (spte & shadow_mmio_mask) == shadow_mmio_value;
+	return (spte & SPTE_SPECIAL_MASK) == SPTE_MMIO_MASK;
 }
 
 static inline bool sp_ad_disabled(struct kvm_mmu_page *sp)
@@ -568,7 +565,6 @@ static void kvm_mmu_reset_all_pte_masks(void)
 	shadow_dirty_mask = 0;
 	shadow_nx_mask = 0;
 	shadow_x_mask = 0;
-	shadow_mmio_mask = 0;
 	shadow_present_mask = 0;
 	shadow_acc_track_mask = 0;
 
@@ -6154,7 +6150,7 @@ static void kvm_set_mmio_spte_mask(void)
 	else
 		mask = 0;
 
-	kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);
+	kvm_mmu_set_mmio_spte_mask(mask, ACC_WRITE_MASK | ACC_USER_MASK);
 }
 
 static bool get_nx_auto_mode(void)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index a862c768fd54..3c9b321a420a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -780,7 +780,7 @@ static __init void svm_adjust_mmio_mask(void)
 	 */
 	mask = (mask_bit < 52) ? rsvd_bits(mask_bit, 51) | PT_PRESENT_MASK : 0;
 
-	kvm_mmu_set_mmio_spte_mask(mask, mask, PT_WRITABLE_MASK | PT_USER_MASK);
+	kvm_mmu_set_mmio_spte_mask(mask, PT_WRITABLE_MASK | PT_USER_MASK);
 }
 
 static void svm_hardware_teardown(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 9b63ac8d97ee..65ff16f00c08 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4147,8 +4147,7 @@ static void ept_set_mmio_spte_mask(void)
 	 * EPT Misconfigurations can be generated if the value of bits 2:0
 	 * of an EPT paging-structure entry is 110b (write/execute).
 	 */
-	kvm_mmu_set_mmio_spte_mask(VMX_EPT_RWX_MASK,
-				   VMX_EPT_MISCONFIG_WX_VALUE, 0);
+	kvm_mmu_set_mmio_spte_mask(VMX_EPT_MISCONFIG_WX_VALUE, 0);
 }
 
 #define VMX_XSS_EXIT_BITMAP 0
-- 
2.26.2