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From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>
Cc: David Hildenbrand <david@kernel.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	 Stefan Teodorescu <fane@google.com>,
	Dennis Tighe <dtighe@google.com>,
	 Sashiko Bot <sashiko-bot@kernel.org>,
	Yan Zhao <yan.y.zhao@intel.com>
Subject: [PATCH 2/2] KVM: guest_memfd: Drop superfluous WRITE_ONCE() when binding a memslot
Date: Wed, 26 Aug 2026 09:51:54 -0700	[thread overview]
Message-ID: <20260826165154.766699-3-seanjc@google.com> (raw)
In-Reply-To: <20260826165154.766699-1-seanjc@google.com>

Drop the superfluous WRITE_ONCE() when setting a memslot's guest_memfd file
during initial binding, as the memslot *must* be inactive and unreachable.
The superfluous WRITE_ONCE() was added by commit 67b43038ce14 ("KVM:
guest_memfd: Remove RCU-protected attribute from slot->gmem.file") to
maintain rough "parity" with the existing rcu_assign_pointer(), not
realizing that the only reason rcu_assign_pointer() was used was to make
sparse and other checkers happy.

Cc: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 virt/kvm/guest_memfd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 1ef9e2916423..1d2de9a1bc3f 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -653,7 +653,7 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
 	 * kvm_gmem_bind() must occur on a new memslot.  Because the memslot
 	 * is not visible yet, kvm_gmem_get_pfn() is guaranteed to see the file.
 	 */
-	WRITE_ONCE(slot->gmem.file, file);
+	slot->gmem.file = file;
 	slot->gmem.pgoff = start;
 	if (kvm_gmem_supports_mmap(inode))
 		slot->flags |= KVM_MEMSLOT_GMEM_ONLY;
-- 
2.55.0.887.g758fc8c411-goog


  parent reply	other threads:[~2026-08-26 16:52 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-26 16:51 [PATCH 0/2] KVM: guest_memfd: Handle xarray binding errors Sean Christopherson
2026-08-26 16:51 ` [PATCH 1/2] KVM: guest_memfd: Gracefully handle xarray errors when binding a memslot Sean Christopherson
2026-08-26 17:05   ` sashiko-bot
2026-08-26 17:17     ` Sean Christopherson
2026-08-26 16:51 ` Sean Christopherson [this message]
2026-08-26 17:05   ` [PATCH 2/2] KVM: guest_memfd: Drop superfluous WRITE_ONCE() " sashiko-bot
2026-08-26 18:36     ` Sean Christopherson

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