linux-kernel - [PATCH v2 12/14] KVM: extend kvm_range_has_memory_attributes() to check subset of attributes

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Message-ID: <20240726185157.72821-13-pbonzini@redhat.com>
Date: Fri, 26 Jul 2024 14:51:55 -0400
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: seanjc@...gle.com,
	michael.roth@....com
Subject: [PATCH v2 12/14] KVM: extend kvm_range_has_memory_attributes() to check subset of attributes

While currently there is no other attribute than KVM_MEMORY_ATTRIBUTE_PRIVATE,
KVM code such as kvm_mem_is_private() is written to expect their existence.
Allow using kvm_range_has_memory_attributes() as a multi-page version of
kvm_mem_is_private(), without it breaking later when more attributes are
introduced.

Reviewed-by: Michael Roth <michael.roth@....com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/mmu/mmu.c   |  2 +-
 include/linux/kvm_host.h |  2 +-
 virt/kvm/kvm_main.c      | 13 +++++++------
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 26ef5b6ac3c1..43a02891babb 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7513,7 +7513,7 @@ static bool hugepage_has_attrs(struct kvm *kvm, struct kvm_memory_slot *slot,
 	const unsigned long end = start + KVM_PAGES_PER_HPAGE(level);
 
 	if (level == PG_LEVEL_2M)
-		return kvm_range_has_memory_attributes(kvm, start, end, attrs);
+		return kvm_range_has_memory_attributes(kvm, start, end, ~0, attrs);
 
 	for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
 		if (hugepage_test_mixed(slot, gfn, level - 1) ||
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 45373d42f314..c223b97df03e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2414,7 +2414,7 @@ static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn
 }
 
 bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-				     unsigned long attrs);
+				     unsigned long mask, unsigned long attrs);
 bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
 					struct kvm_gfn_range *range);
 bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 30328ff2d840..92901656a0d4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2408,21 +2408,21 @@ static u64 kvm_supported_mem_attributes(struct kvm *kvm)
 
 /*
  * Returns true if _all_ gfns in the range [@start, @end) have attributes
- * matching @attrs.
+ * such that the bits in @mask match @attrs.
  */
 bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
-				     unsigned long attrs)
+				     unsigned long mask, unsigned long attrs)
 {
 	XA_STATE(xas, &kvm->mem_attr_array, start);
-	unsigned long mask = kvm_supported_mem_attributes(kvm);
 	unsigned long index;
 	void *entry;
 
+	mask &= kvm_supported_mem_attributes(kvm);
 	if (attrs & ~mask)
 		return false;
 
 	if (end == start + 1)
-		return kvm_get_memory_attributes(kvm, start) == attrs;
+		return (kvm_get_memory_attributes(kvm, start) & mask) == attrs;
 
 	guard(rcu)();
 	if (!attrs)
@@ -2433,7 +2433,8 @@ bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 			entry = xas_next(&xas);
 		} while (xas_retry(&xas, entry));
 
-		if (xas.xa_index != index || xa_to_value(entry) != attrs)
+		if (xas.xa_index != index ||
+		    (xa_to_value(entry) & mask) != attrs)
 			return false;
 	}
 
@@ -2532,7 +2533,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 	mutex_lock(&kvm->slots_lock);
 
 	/* Nothing to do if the entire range as the desired attributes. */
-	if (kvm_range_has_memory_attributes(kvm, start, end, attributes))
+	if (kvm_range_has_memory_attributes(kvm, start, end, ~0, attributes))
 		goto out_unlock;
 
 	/*
-- 
2.43.0