[RFC PATCH 12/18] KVM: x86/mmu: Introduce shadow_ux_mask

[Jon Kohler <jon@nutanix.com>]

Add shadow_ux_mask to spte, to keep track of user executable pages
used by Intel MBEC.

Since masks are setup outside of vcpu creation, plumb in general
system level enablement from vmx code into kvm_mmu_set_ept_masks().

Signed-off-by: Jon Kohler <jon@nutanix.com>
Co-developed-by: Sergey Dyasli <sergey.dyasli@nutanix.com>
Signed-off-by: Sergey Dyasli <sergey.dyasli@nutanix.com>

---
 arch/x86/kvm/mmu.h      |  3 ++-
 arch/x86/kvm/mmu/spte.c | 21 ++++++++++++++++++---
 arch/x86/kvm/mmu/spte.h |  1 +
 arch/x86/kvm/vmx/vmx.c  |  3 ++-
 4 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 9dc5dd43ae7f..d10c37db7653 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -79,7 +79,8 @@ u8 kvm_mmu_get_max_tdp_level(void);
 
 void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask);
 void kvm_mmu_set_me_spte_mask(u64 me_value, u64 me_mask);
-void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only);
+void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only,
+			   bool has_guest_exec_ctrl);
 
 void kvm_init_mmu(struct kvm_vcpu *vcpu);
 void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 8f7eb3ad88fc..6f4994b3e6d0 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -28,6 +28,7 @@ u64 __read_mostly shadow_host_writable_mask;
 u64 __read_mostly shadow_mmu_writable_mask;
 u64 __read_mostly shadow_nx_mask;
 u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
+u64 __read_mostly shadow_ux_mask;
 u64 __read_mostly shadow_user_mask;
 u64 __read_mostly shadow_accessed_mask;
 u64 __read_mostly shadow_dirty_mask;
@@ -313,8 +314,14 @@ u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte,
 		 * the page executable as the NX hugepage mitigation no longer
 		 * applies.
 		 */
-		if ((role.access & ACC_EXEC_MASK) && is_nx_huge_page_enabled(kvm))
+		if ((role.access & ACC_EXEC_MASK) && is_nx_huge_page_enabled(kvm)) {
 			child_spte = make_spte_executable(child_spte);
+			// TODO: For LKML: switch to vcpu->arch.pt_guest_exec_control? up
+			// for suggestions on how best to toggle this.
+			if (enable_pt_guest_exec_control &&
+			    role.access & ACC_USER_EXEC_MASK)
+				child_spte |= shadow_ux_mask;
+		}
 	}
 
 	return child_spte;
@@ -326,7 +333,7 @@ u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled)
 	u64 spte = SPTE_MMU_PRESENT_MASK;
 
 	spte |= __pa(child_pt) | shadow_present_mask | PT_WRITABLE_MASK |
-		shadow_user_mask | shadow_x_mask | shadow_me_value;
+		shadow_user_mask | shadow_x_mask | shadow_ux_mask | shadow_me_value;
 
 	if (ad_disabled)
 		spte |= SPTE_TDP_AD_DISABLED;
@@ -420,7 +427,8 @@ void kvm_mmu_set_me_spte_mask(u64 me_value, u64 me_mask)
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_set_me_spte_mask);
 
-void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only)
+void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only,
+			   bool has_guest_exec_ctrl)
 {
 	shadow_user_mask	= VMX_EPT_READABLE_MASK;
 	shadow_accessed_mask	= has_ad_bits ? VMX_EPT_ACCESS_BIT : 0ull;
@@ -428,8 +436,14 @@ void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only)
 	shadow_nx_mask		= 0ull;
 	shadow_x_mask		= VMX_EPT_EXECUTABLE_MASK;
 	/* VMX_EPT_SUPPRESS_VE_BIT is needed for W or X violation. */
+	// For LKML Review:
+	// Do we need to modify shadow_present_mask in the MBEC case?
 	shadow_present_mask	=
 		(has_exec_only ? 0ull : VMX_EPT_READABLE_MASK) | VMX_EPT_SUPPRESS_VE_BIT;
+
+	shadow_ux_mask		=
+		has_guest_exec_ctrl ? VMX_EPT_USER_EXECUTABLE_MASK : 0ull;
+
 	/*
 	 * EPT overrides the host MTRRs, and so KVM must program the desired
 	 * memtype directly into the SPTEs.  Note, this mask is just the mask
@@ -484,6 +498,7 @@ void kvm_mmu_reset_all_pte_masks(void)
 	shadow_dirty_mask	= PT_DIRTY_MASK;
 	shadow_nx_mask		= PT64_NX_MASK;
 	shadow_x_mask		= 0;
+	shadow_ux_mask		= 0;
 	shadow_present_mask	= PT_PRESENT_MASK;
 
 	/*
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index d9e22133b6d0..dc2f0dc9c46e 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -171,6 +171,7 @@ extern u64 __read_mostly shadow_mmu_writable_mask;
 extern u64 __read_mostly shadow_nx_mask;
 extern u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
 extern u64 __read_mostly shadow_user_mask;
+extern u64 __read_mostly shadow_ux_mask;
 extern u64 __read_mostly shadow_accessed_mask;
 extern u64 __read_mostly shadow_dirty_mask;
 extern u64 __read_mostly shadow_mmio_value;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0aadfa924045..d16e3f170258 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8544,7 +8544,8 @@ __init int vmx_hardware_setup(void)
 
 	if (enable_ept)
 		kvm_mmu_set_ept_masks(enable_ept_ad_bits,
-				      cpu_has_vmx_ept_execute_only());
+				      cpu_has_vmx_ept_execute_only(),
+				      enable_pt_guest_exec_control);
 
 	/*
 	 * Setup shadow_me_value/shadow_me_mask to include MKTME KeyID
-- 
2.43.0