[PATCH 11/12] KVM: extend kvm_range_has_memory_attributes() to check subset of attributes

Paolo Bonzini
2024-07-11T22:28:09Z

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.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.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 4e0e9963066f..f6b7391fe438 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7524,7 +7524,7 @@ 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 f6e11991442d..456dbdf7aaaf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2410,7 +2410,7 @@ 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 8ab9d8ff7b74..62e5d9b0ae83 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2402,21 +2402,21 @@ 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)
@@ -2427,7 +2427,8 @@ 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;
}

@@ -2526,7 +2527,7 @@ 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