[PATCH v2 2/5] KVM: Assert slots_lock is held when setting memory regions

Sean Christopherson
2025-01-11T00:20:28Z

Add proper lockdep assertions in __kvm_set_memory_region() and
__x86_set_memory_region() instead of relying comments.

Opportunistically delete __kvm_set_memory_region()'s entire function
comment as the API doesn't allocate memory or select a gfn, and the
"mostly for framebuffers" comment hasn't been true for a very long time.

Cc: Tao Su <tao1.su@linux.intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 3 ++-
virt/kvm/kvm_main.c | 10 ++--------
2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1b04092ec76a..a861287a67bd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12793,7 +12793,8 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,
struct kvm_memslots *slots = kvm_memslots(kvm);
struct kvm_memory_slot *slot;

- /* Called with kvm->slots_lock held. */
+ lockdep_assert_held(&kvm->slots_lock);
+
if (WARN_ON(id >= KVM_MEM_SLOTS_NUM))
return ERR_PTR_USR(-EINVAL);

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index eb3d0a385077..7d25b50cb298 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1926,14 +1926,6 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
return false;
}

-/*
- * Allocate some memory and give it an address in the guest physical address
- * space.
- *
- * Discontiguous memory is allowed, mostly for framebuffers.
- *
- * Must be called holding kvm->slots_lock for write.
- */
int __kvm_set_memory_region(struct kvm *kvm,
const struct kvm_userspace_memory_region2 *mem)
{
@@ -1945,6 +1937,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
int as_id, id;
int r;

+ lockdep_assert_held(&kvm->slots_lock);
+
r = check_memory_region_flags(kvm, mem);
if (r)
return r;
--
2.47.1.613.gc27f4b7a9f-goog