[PATCH 16/45] KVM: adjust for presence of more than one attribute

[Paolo Bonzini]

Remove or adjust code that assumed that the only valid attribute was
KVM_MEMORY_ATTRIBUTE_PRIVATE, in preparation for the introduction of RWX
memory attributes.

In particular, the optimization in kvm_range_has_memory_attributes
simply is not valid if attrs == 0 but some of the attributes are being
ignored.  The WARNs in arch/x86/kvm/mmu/mmu.c are just a duplicate of
checking kvm_supported_mem_attributes() during the ioctl, so drop it.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Link: https://patch.msgid.link/20260918135030.171564-13-pbonzini@xxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/mmu.c |  9 +--------
 virt/kvm/kvm_main.c    | 10 +++++++---
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 3755393de4ca..b89517794034 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -8226,9 +8226,6 @@ bool kvm_arch_pre_set_vm_memory_attributes(struct kvm *kvm,
 	 * Zapping SPTEs in this case ensures KVM will reassess whether or not
 	 * a hugepage can be used for affected ranges.
 	 */
-	if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
-		return false;
-
 	if (WARN_ON_ONCE(range->end <= range->start))
 		return false;
 
@@ -8304,11 +8301,7 @@ bool kvm_arch_post_set_vm_memory_attributes(struct kvm *kvm,
 	 * can't map memory PRIVATE.  KVM mustn't create a SHARED hugepage over
 	 * a range that has PRIVATE GFNs, and conversely converting a range to
 	 * SHARED may now allow hugepages.
-	 */
-	if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
-		return false;
-
-	/*
+	 *
 	 * The sequence matters here: upper levels consume the result of lower
 	 * level's scanning.
 	 */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2fd595a901bd..17341c689d11 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2490,10 +2490,12 @@ bool kvm_range_has_vm_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 					unsigned long mask, unsigned long attrs)
 {
 	XA_STATE(xas, &kvm->mem_attr_array, start);
+	unsigned long supported_attrs;
 	unsigned long index;
 	void *entry;
 
-	mask &= kvm_supported_vm_mem_attributes(kvm);
+	supported_attrs = kvm_supported_vm_mem_attributes(kvm);
+	mask &= supported_attrs;
 	if (attrs & ~mask)
 		return false;
 
@@ -2522,8 +2524,10 @@ bool kvm_range_has_vm_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 	 */
 	for (index = start; index < end; index++) {
 		do {
-			entry = attrs ? xas_next(&xas) :
-					xas_next_entry(&xas, end - 1);
+			if (!attrs && mask == supported_attrs)
+				entry = xas_next_entry(&xas, end - 1);
+			else
+				entry = xas_next(&xas);
 		} while (xas_retry(&xas, entry));
 
 		if (!entry)
-- 
2.52.0