| Message ID | 20240404185034.3184582-6-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: guest_memfd: New hooks and functionality for SEV-SNP and TDX | expand |
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 409cf9b51313..e5b3cd02b651 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -499,7 +499,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gmem = file->private_data; - if (WARN_ON_ONCE(xa_load(&gmem->bindings, index) != slot)) { + if (xa_load(&gmem->bindings, index) != slot) { + WARN_ON_ONCE(xa_load(&gmem->bindings, index)); r = -EIO; goto out_fput; }
Because kvm_gmem_get_pfn() is called from the page fault path without any of the slots_lock, filemap lock or mmu_lock taken, it is possible for it to race with kvm_gmem_unbind(). This is not a problem, as any PTE that is installed temporarily will be zapped before the guest has the occasion to run. However, it is not possible to have a complete unbind+bind racing with the page fault, because deleting the memslot will call synchronize_srcu_expedited() and wait for the page fault to be resolved. Thus, we can still warn if the file is there and is not the one we expect. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- virt/kvm/guest_memfd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)