KVM: x86/mmu: Allow the roots to be invalid in FNAME(invlpg)

Don't assume the current root to be valid, just check it and remove
the WARN().

Also move the code to check if the root is valid into FNAME(invlpg)
to simplify the code.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Link: https://lore.kernel.org/r/20230216235321.735214-2-jiangshanlai@gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: Lai Jiangshan

arch/x86/kvm/mmu/mmu.c

@@ -5787,8 +5787,7 @@ void kvm_mmu_invalidate_addr(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 		mmu->invlpg(vcpu, addr, mmu->root.hpa);
 
 	for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
-		if ((roots & KVM_MMU_ROOT_PREVIOUS(i)) &&
-		    VALID_PAGE(mmu->prev_roots[i].hpa))
+		if (roots & KVM_MMU_ROOT_PREVIOUS(i))
 			mmu->invlpg(vcpu, addr, mmu->prev_roots[i].hpa);
 	}
 }

arch/x86/kvm/mmu/paging_tmpl.h

@@ -863,10 +863,8 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, u64 addr, hpa_t root_hpa)
 	 */
 	mmu_topup_memory_caches(vcpu, true);
 
-	if (!VALID_PAGE(root_hpa)) {
-		WARN_ON(1);
+	if (!VALID_PAGE(root_hpa))
 		return;
-	}
 
 	write_lock(&vcpu->kvm->mmu_lock);
 	for_each_shadow_entry_using_root(vcpu, root_hpa, addr, iterator) {