Merge tag 'kvm-x86-vmx-6.16' of https://github.com/kvm-x86/linux into HEAD

KVM VMX changes for 6.16:

 - Explicitly check MSR load/store list counts to fix a potential overflow on
   32-bit kernels.

 - Flush shadow VMCSes on emergency reboot.

 - Revert mem_enc_ioctl() back to an optional hook, as it's nullified when
   SEV or TDX is disabled via Kconfig.

 - Macrofy the handling of vt_x86_ops to eliminate a pile of boilerplate code
   needed for TDX, and to optimize CONFIG_KVM_INTEL_TDX=n builds.

1 files changed, 20 insertions, 11 deletions

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 4b3fe437a5a1..b50f9c894ab8 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -824,12 +824,30 @@ static int nested_vmx_check_apicv_controls(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+static u32 nested_vmx_max_atomic_switch_msrs(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	u64 vmx_misc = vmx_control_msr(vmx->nested.msrs.misc_low,
+				       vmx->nested.msrs.misc_high);
+
+	return (vmx_misc_max_msr(vmx_misc) + 1) * VMX_MISC_MSR_LIST_MULTIPLIER;
+}
+
 static int nested_vmx_check_msr_switch(struct kvm_vcpu *vcpu,
 				       u32 count, u64 addr)
 {
 	if (count == 0)
 		return 0;
 
+	/*
+	 * Exceeding the limit results in architecturally _undefined_ behavior,
+	 * i.e. KVM is allowed to do literally anything in response to a bad
+	 * limit.  Immediately generate a consistency check so that code that
+	 * consumes the count doesn't need to worry about extreme edge cases.
+	 */
+	if (count > nested_vmx_max_atomic_switch_msrs(vcpu))
+		return -EINVAL;
+
 	if (!kvm_vcpu_is_legal_aligned_gpa(vcpu, addr, 16) ||
 	    !kvm_vcpu_is_legal_gpa(vcpu, (addr + count * sizeof(struct vmx_msr_entry) - 1)))
 		return -EINVAL;
@@ -940,15 +958,6 @@ static int nested_vmx_store_msr_check(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-static u32 nested_vmx_max_atomic_switch_msrs(struct kvm_vcpu *vcpu)
-{
-	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	u64 vmx_misc = vmx_control_msr(vmx->nested.msrs.misc_low,
-				       vmx->nested.msrs.misc_high);
-
-	return (vmx_misc_max_msr(vmx_misc) + 1) * VMX_MISC_MSR_LIST_MULTIPLIER;
-}
-
 /*
  * Load guest's/host's msr at nested entry/exit.
  * return 0 for success, entry index for failure.
@@ -965,7 +974,7 @@ static u32 nested_vmx_load_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
 	u32 max_msr_list_size = nested_vmx_max_atomic_switch_msrs(vcpu);
 
 	for (i = 0; i < count; i++) {
-		if (unlikely(i >= max_msr_list_size))
+		if (WARN_ON_ONCE(i >= max_msr_list_size))
 			goto fail;
 
 		if (kvm_vcpu_read_guest(vcpu, gpa + i * sizeof(e),
@@ -1053,7 +1062,7 @@ static int nested_vmx_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
 	u32 max_msr_list_size = nested_vmx_max_atomic_switch_msrs(vcpu);
 
 	for (i = 0; i < count; i++) {
-		if (unlikely(i >= max_msr_list_size))
+		if (WARN_ON_ONCE(i >= max_msr_list_size))
 			return -EINVAL;
 
 		if (!read_and_check_msr_entry(vcpu, gpa, i, &e))