KVM: TDX: Return -EIO, not -EINVAL, on a KVM_BUG_ON() condition

Return -EIO when a KVM_BUG_ON() is tripped, as KVM's ABI is to return -EIO
when a VM has been killed due to a KVM bug, not -EINVAL.  Note, many (all?)
of the affected paths never propagate the error code to userspace, i.e.
this is about internal consistency more than anything else.

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251030200951.3402865-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/vmx/tdx.c

@@ -1621,7 +1621,7 @@ static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn,
 	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
 
 	if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm))
-		return -EINVAL;
+		return -EIO;
 
 	/* nr_premapped will be decreased when tdh_mem_page_add() is called. */
 	atomic64_inc(&kvm_tdx->nr_premapped);
@@ -1635,7 +1635,7 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
 
 	/* TODO: handle large pages. */
 	if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
-		return -EINVAL;
+		return -EIO;
 
 	/*
 	 * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching
@@ -1658,10 +1658,10 @@ static int tdx_sept_drop_private_spte(struct kvm *kvm, gfn_t gfn,
 
 	/* TODO: handle large pages. */
 	if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
-		return -EINVAL;
+		return -EIO;
 
 	if (KVM_BUG_ON(!is_hkid_assigned(kvm_tdx), kvm))
-		return -EINVAL;
+		return -EIO;
 
 	/*
 	 * When zapping private page, write lock is held. So no race condition
@@ -1846,7 +1846,7 @@ static int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn,
 	 * and slot move/deletion.
 	 */
 	if (KVM_BUG_ON(is_hkid_assigned(kvm_tdx), kvm))
-		return -EINVAL;
+		return -EIO;
 
 	/*
 	 * The HKID assigned to this TD was already freed and cache was
@@ -1867,7 +1867,7 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
 	 * there can't be anything populated in the private EPT.
 	 */
 	if (KVM_BUG_ON(!is_hkid_assigned(to_kvm_tdx(kvm)), kvm))
-		return -EINVAL;
+		return -EIO;
 
 	ret = tdx_sept_zap_private_spte(kvm, gfn, level, page);
 	if (ret <= 0)