Merge tag 'kvm-x86-vmx-6.15' of https://github.com/kvm-x86/linux into HEAD

KVM VMX changes for 6.15

 - Fix a bug where KVM unnecessarily reads XFD_ERR from hardware and thus
   modifies the vCPU's XFD_ERR on a #NM due to CR0.TS=1.

 - Pass XFD_ERR as a psueo-payload when injecting #NM as a preparatory step
   for upcoming FRED virtualization support.

 - Decouple the EPT entry RWX protection bit macros from the EPT Violation bits
   as a general cleanup, and in anticipation of adding support for emulating
   Mode-Based Execution (MBEC).

 - Reject KVM_RUN if userspace manages to gain control and stuff invalid guest
   state while KVM is in the middle of emulating nested VM-Enter.

 - Add a macro to handle KVM's sanity checks on entry/exit VMCS control pairs
   in anticipation of adding sanity checks for secondary exit controls (the
   primary field is out of bits).

Author: bonzini

arch/x86/include/asm/vmx.h

@@ -580,18 +580,22 @@ enum vm_entry_failure_code {
 /*
  * Exit Qualifications for EPT Violations
  */
-#define EPT_VIOLATION_ACC_READ_BIT	0
-#define EPT_VIOLATION_ACC_WRITE_BIT	1
-#define EPT_VIOLATION_ACC_INSTR_BIT	2
-#define EPT_VIOLATION_RWX_SHIFT		3
-#define EPT_VIOLATION_GVA_IS_VALID_BIT	7
-#define EPT_VIOLATION_GVA_TRANSLATED_BIT 8
-#define EPT_VIOLATION_ACC_READ		(1 << EPT_VIOLATION_ACC_READ_BIT)
-#define EPT_VIOLATION_ACC_WRITE		(1 << EPT_VIOLATION_ACC_WRITE_BIT)
-#define EPT_VIOLATION_ACC_INSTR		(1 << EPT_VIOLATION_ACC_INSTR_BIT)
-#define EPT_VIOLATION_RWX_MASK		(VMX_EPT_RWX_MASK << EPT_VIOLATION_RWX_SHIFT)
-#define EPT_VIOLATION_GVA_IS_VALID	(1 << EPT_VIOLATION_GVA_IS_VALID_BIT)
-#define EPT_VIOLATION_GVA_TRANSLATED	(1 << EPT_VIOLATION_GVA_TRANSLATED_BIT)
+#define EPT_VIOLATION_ACC_READ		BIT(0)
+#define EPT_VIOLATION_ACC_WRITE		BIT(1)
+#define EPT_VIOLATION_ACC_INSTR		BIT(2)
+#define EPT_VIOLATION_PROT_READ		BIT(3)
+#define EPT_VIOLATION_PROT_WRITE	BIT(4)
+#define EPT_VIOLATION_PROT_EXEC		BIT(5)
+#define EPT_VIOLATION_PROT_MASK		(EPT_VIOLATION_PROT_READ  | \
+					 EPT_VIOLATION_PROT_WRITE | \
+					 EPT_VIOLATION_PROT_EXEC)
+#define EPT_VIOLATION_GVA_IS_VALID	BIT(7)
+#define EPT_VIOLATION_GVA_TRANSLATED	BIT(8)
+
+#define EPT_VIOLATION_RWX_TO_PROT(__epte) (((__epte) & VMX_EPT_RWX_MASK) << 3)
+
+static_assert(EPT_VIOLATION_RWX_TO_PROT(VMX_EPT_RWX_MASK) ==
+	      (EPT_VIOLATION_PROT_READ | EPT_VIOLATION_PROT_WRITE | EPT_VIOLATION_PROT_EXEC));
 
 /*
  * Exit Qualifications for NOTIFY VM EXIT

arch/x86/kvm/mmu/paging_tmpl.h

@@ -510,8 +510,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 		 * Note, pte_access holds the raw RWX bits from the EPTE, not
 		 * ACC_*_MASK flags!
 		 */
-		walker->fault.exit_qualification |= (pte_access & VMX_EPT_RWX_MASK) <<
-						     EPT_VIOLATION_RWX_SHIFT;
+		walker->fault.exit_qualification |= EPT_VIOLATION_RWX_TO_PROT(pte_access);
 	}
 #endif
 	walker->fault.address = addr;

arch/x86/kvm/vmx/vmx.c

@@ -2578,6 +2578,34 @@ static u64 adjust_vmx_controls64(u64 ctl_opt, u32 msr)
 	return  ctl_opt & allowed;
 }
 
+#define vmx_check_entry_exit_pairs(pairs, entry_controls, exit_controls)	\
+({										\
+	int i, r = 0;								\
+										\
+	BUILD_BUG_ON(sizeof(pairs[0].entry_control) != sizeof(entry_controls));	\
+	BUILD_BUG_ON(sizeof(pairs[0].exit_control)  != sizeof(exit_controls));	\
+										\
+	for (i = 0; i < ARRAY_SIZE(pairs); i++) {				\
+		typeof(entry_controls) n_ctrl = pairs[i].entry_control;		\
+		typeof(exit_controls) x_ctrl = pairs[i].exit_control;		\
+										\
+		if (!(entry_controls & n_ctrl) == !(exit_controls & x_ctrl))	\
+			continue;						\
+										\
+		pr_warn_once("Inconsistent VM-Entry/VM-Exit pair, "		\
+			     "entry = %llx (%llx), exit = %llx (%llx)\n",	\
+			     (u64)(entry_controls & n_ctrl), (u64)n_ctrl,	\
+			     (u64)(exit_controls & x_ctrl), (u64)x_ctrl);	\
+										\
+		if (error_on_inconsistent_vmcs_config)				\
+			r = -EIO;						\
+										\
+		entry_controls &= ~n_ctrl;					\
+		exit_controls &= ~x_ctrl;					\
+	}									\
+	r;									\
+})
+
 static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 			     struct vmx_capability *vmx_cap)
 {
@@ -2589,7 +2617,6 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 	u32 _vmentry_control = 0;
 	u64 basic_msr;
 	u64 misc_msr;
-	int i;
 
 	/*
 	 * LOAD/SAVE_DEBUG_CONTROLS are absent because both are mandatory.
@@ -2693,22 +2720,9 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 				&_vmentry_control))
 		return -EIO;
 
-	for (i = 0; i < ARRAY_SIZE(vmcs_entry_exit_pairs); i++) {
-		u32 n_ctrl = vmcs_entry_exit_pairs[i].entry_control;
-		u32 x_ctrl = vmcs_entry_exit_pairs[i].exit_control;
-
-		if (!(_vmentry_control & n_ctrl) == !(_vmexit_control & x_ctrl))
-			continue;
-
-		pr_warn_once("Inconsistent VM-Entry/VM-Exit pair, entry = %x, exit = %x\n",
-			     _vmentry_control & n_ctrl, _vmexit_control & x_ctrl);
-
-		if (error_on_inconsistent_vmcs_config)
-			return -EIO;
-
-		_vmentry_control &= ~n_ctrl;
-		_vmexit_control &= ~x_ctrl;
-	}
+	if (vmx_check_entry_exit_pairs(vmcs_entry_exit_pairs,
+				       _vmentry_control, _vmexit_control))
+		return -EIO;
 
 	/*
 	 * Some cpus support VM_{ENTRY,EXIT}_IA32_PERF_GLOBAL_CTRL but they
@@ -5211,6 +5225,12 @@ bool vmx_guest_inject_ac(struct kvm_vcpu *vcpu)
 	       (kvm_get_rflags(vcpu) & X86_EFLAGS_AC);
 }
 
+static bool is_xfd_nm_fault(struct kvm_vcpu *vcpu)
+{
+	return vcpu->arch.guest_fpu.fpstate->xfd &&
+	       !kvm_is_cr0_bit_set(vcpu, X86_CR0_TS);
+}
+
 static int handle_exception_nmi(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -5237,7 +5257,8 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
 	 * point.
 	 */
 	if (is_nm_fault(intr_info)) {
-		kvm_queue_exception(vcpu, NM_VECTOR);
+		kvm_queue_exception_p(vcpu, NM_VECTOR,
+				      is_xfd_nm_fault(vcpu) ? vcpu->arch.guest_fpu.xfd_err : 0);
 		return 1;
 	}
 
@@ -5817,7 +5838,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
 	error_code |= (exit_qualification & EPT_VIOLATION_ACC_INSTR)
 		      ? PFERR_FETCH_MASK : 0;
 	/* ept page table entry is present? */
-	error_code |= (exit_qualification & EPT_VIOLATION_RWX_MASK)
+	error_code |= (exit_qualification & EPT_VIOLATION_PROT_MASK)
 		      ? PFERR_PRESENT_MASK : 0;
 
 	if (error_code & EPT_VIOLATION_GVA_IS_VALID)
@@ -5871,11 +5892,35 @@ static int handle_nmi_window(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
-static bool vmx_emulation_required_with_pending_exception(struct kvm_vcpu *vcpu)
+/*
+ * Returns true if emulation is required (due to the vCPU having invalid state
+ * with unsrestricted guest mode disabled) and KVM can't faithfully emulate the
+ * current vCPU state.
+ */
+static bool vmx_unhandleable_emulation_required(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-	return vmx->emulation_required && !vmx->rmode.vm86_active &&
+	if (!vmx->emulation_required)
+		return false;
+
+	/*
+	 * It is architecturally impossible for emulation to be required when a
+	 * nested VM-Enter is pending completion, as VM-Enter will VM-Fail if
+	 * guest state is invalid and unrestricted guest is disabled, i.e. KVM
+	 * should synthesize VM-Fail instead emulation L2 code.  This path is
+	 * only reachable if userspace modifies L2 guest state after KVM has
+	 * performed the nested VM-Enter consistency checks.
+	 */
+	if (vmx->nested.nested_run_pending)
+		return true;
+
+	/*
+	 * KVM only supports emulating exceptions if the vCPU is in Real Mode.
+	 * If emulation is required, KVM can't perform a successful VM-Enter to
+	 * inject the exception.
+	 */
+	return !vmx->rmode.vm86_active &&
 	       (kvm_is_exception_pending(vcpu) || vcpu->arch.exception.injected);
 }
 
@@ -5898,7 +5943,7 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 		if (!kvm_emulate_instruction(vcpu, 0))
 			return 0;
 
-		if (vmx_emulation_required_with_pending_exception(vcpu)) {
+		if (vmx_unhandleable_emulation_required(vcpu)) {
 			kvm_prepare_emulation_failure_exit(vcpu);
 			return 0;
 		}
@@ -5922,7 +5967,7 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 
 int vmx_vcpu_pre_run(struct kvm_vcpu *vcpu)
 {
-	if (vmx_emulation_required_with_pending_exception(vcpu)) {
+	if (vmx_unhandleable_emulation_required(vcpu)) {
 		kvm_prepare_emulation_failure_exit(vcpu);
 		return 0;
 	}
@@ -6997,16 +7042,15 @@ static void handle_nm_fault_irqoff(struct kvm_vcpu *vcpu)
 	 * MSR value is not clobbered by the host activity before the guest
 	 * has chance to consume it.
 	 *
-	 * Do not blindly read xfd_err here, since this exception might
-	 * be caused by L1 interception on a platform which doesn't
-	 * support xfd at all.
-	 *
-	 * Do it conditionally upon guest_fpu::xfd. xfd_err matters
-	 * only when xfd contains a non-zero value.
+	 * Update the guest's XFD_ERR if and only if XFD is enabled, as the #NM
+	 * interception may have been caused by L1 interception.  Per the SDM,
+	 * XFD_ERR is not modified for non-XFD #NM, i.e. if CR0.TS=1.
 	 *
-	 * Queuing exception is done in vmx_handle_exit. See comment there.
+	 * Note, XFD_ERR is updated _before_ the #NM interception check, i.e.
+	 * unlike CR2 and DR6, the value is not a payload that is attached to
+	 * the #NM exception.
 	 */
-	if (vcpu->arch.guest_fpu.fpstate->xfd)
+	if (is_xfd_nm_fault(vcpu))
 		rdmsrl(MSR_IA32_XFD_ERR, vcpu->arch.guest_fpu.xfd_err);
 }