From nobody Sat Feb 7 22:21:25 2026 Received: from mail-pg1-f201.google.com (mail-pg1-f201.google.com [209.85.215.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C6F0D2475CE for ; Tue, 7 Oct 2025 22:24:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759875842; cv=none; b=j/OdeKH3A9rLkhdCoJjeugvGWGKtHJ8walMeBXqKZD9+0KmoSKLfvaLLbb+pa/52NwUYH1nb+LK0tX63kKCMSgCLs0MwvvJrSucj34z6uCl+AJo1A+eAu1kDNWTI6Q9wNGn1zZsF/gr8vRNO2SuDJlO4Z/186ediQKZOQH+7XNI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759875842; c=relaxed/simple; bh=iTs5oVgRFI5i7Id7pBmKWAvJOIiaSNf/FcvJpYTbgXc=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=IqArYWzkdhgGLSfCLParjC3tuvFuwgCkKzyrzVs8C1T/hJ1lfn1JBjNIrcJEI9OVX3ORZMiRBGux/iULbU0Bf4V4jgXAz+wnJTjXf6GQR9kZsLityHKcMPA8KhGpqADliGU9RdlYvNbYsu7E7m1gC4TxuVKOGDA+9S+3ggVvjUw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=MiXN+BvG; arc=none smtp.client-ip=209.85.215.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MiXN+BvG" Received: by mail-pg1-f201.google.com with SMTP id 41be03b00d2f7-b4c72281674so4253315a12.3 for ; Tue, 07 Oct 2025 15:24:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1759875840; x=1760480640; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:reply-to:from:to:cc :subject:date:message-id:reply-to; bh=KzhA3wq+r3uRjE3qvTCw8lzfD+9cuHGzBHwE0Qeo1M4=; b=MiXN+BvGJ6+5PY4ZOzYQQjAdDZoFseQEqTn4wp8N1FO24WGUyH06CdwOTE/LaaPMJh n5x793lws6sTP1MxezEZA0oZee2GYqRibvVYIlue6N9Oi9kcH7H+Zf1eBFZwjpvqYYre S/B9ftMwUMzMj8EX797hN3494bxzXUK/Sj4IIP5SiqczslQDZcjAY/LP8DY9IQKMULCa pRX8unmXD6q7F+BGQTHBNBkY+lPC8NzfplNJo3G70r/0dMvhjD9gOdEd1ZqjZpdbyUhC GNeWR1U2X8mlUQ8oIElzUmqQB5BoRA/VbVZdRwfk1i1N858uYNnLag5pU56d+aMNCU/5 syaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759875840; x=1760480640; h=cc:to:from:subject:message-id:mime-version:date:reply-to :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=KzhA3wq+r3uRjE3qvTCw8lzfD+9cuHGzBHwE0Qeo1M4=; b=PYmFigcv9K9CWxOXVyV1oJpKo6GSPft4YRjkxMhQNiFGPsyyTPBQOwsKWwDWJLoAXI Bl8/iIf9/OY75F5zRTvM77yGetESx03fb/NG0oNfEPD3NlyrRK7/Ooq71BXIQhyLdSD0 JXraeuVUkIjU1zhSq6aWep6Pu9TCbWpNFPPh03jkfz8dPFntxTel73DaCUdIi8jZLTBI ecv7NzJqxKM6AW/pdaSrf8TPodZoiACcSA18g/j5DojMmOHpi35uMXSqHlGg7Z17aaXb c/hwqLTJrtLYXlXn42Vp2edTqKhg4jo+RrBxFXID6EfkA9G+UyIB3bJMnpE4874epJ3W /rhg== X-Forwarded-Encrypted: i=1; AJvYcCW+e2hwW0bv/+MngMoYWrnuONhD/aPwT/1W29T2/sqNlEHTObHtsPSSMBRsFMwEczFnBCSPQNqBbcIM9Fs=@vger.kernel.org X-Gm-Message-State: AOJu0YznQB1YiSJZlLV6BDRFV8A+b303kak54hNqpOmFMVRdALfSOFHI zAHpi6VeAzgHot+DUBBhPeZCJo8L5ZqXjd3Zxo2bM+nn2PqH4/WsFIsD5WoTCuKK2ZGlP/1yTkU Uct/6PA== X-Google-Smtp-Source: AGHT+IE4QVI1fKmkMmpPcyCsJDlUuuYAQPHzGkfjzS/K0R0jvy8kCbAQh/LA65MWrxF7bbEW5Xy/CB+i7ro= X-Received: from pjbgl14.prod.google.com ([2002:a17:90b:120e:b0:32e:e4e6:ecfe]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:fa7:b0:275:f156:965c with SMTP id d9443c01a7336-2902741e441mr15340135ad.52.1759875840026; Tue, 07 Oct 2025 15:24:00 -0700 (PDT) Reply-To: Sean Christopherson Date: Tue, 7 Oct 2025 15:23:56 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.51.0.710.ga91ca5db03-goog Message-ID: <20251007222356.348349-1-seanjc@google.com> Subject: [PATCH] KVM: guest_memfd: Define a CLASS to get+put guest_memfd file from a memslot From: Sean Christopherson To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a CLASS to handle getting and putting a guest_memfd file given a memslot to reduce the amount of related boilerplate, and more importantly to minimize the chances of forgetting to put the file (thankfully the bug that prompted this didn't escape initial testing). Define a CLASS instead of using __free(fput) as _free() comes with subtle caveats related to FILO ordering (objects are freed in the order in which they are declared), and the recommended solution/workaround (declare file pointers exactly when they are initialized) is visually jarring relative to KVM's (and the kernel's) overall strict adherence to not mixing declarations and code. E.g. the use in kvm_gmem_populate() would be: slot =3D gfn_to_memslot(kvm, start_gfn); if (!kvm_slot_has_gmem(slot)) return -EINVAL; struct file *file __free(fput) =3D kvm_gmem_get_file(slot; if (!file) return -EFAULT; filemap_invalidate_lock(file->f_mapping); Note, using CLASS() still declares variables in the middle of code, but the syntactic sugar obfuscates the declaration, i.e. hides the anomaly to a large extent. No functional change intended. Signed-off-by: Sean Christopherson Reviewed-by: Ackerley Tng --- virt/kvm/guest_memfd.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 94bafd6c558c..130244e46326 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -307,6 +307,9 @@ static inline struct file *kvm_gmem_get_file(struct kvm= _memory_slot *slot) return get_file_active(&slot->gmem.file); } =20 +DEFINE_CLASS(gmem_get_file, struct file *, if (_T) fput(_T), + kvm_gmem_get_file(slot), struct kvm_memory_slot *slot); + static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn) { return gfn - slot->base_gfn + slot->gmem.pgoff; @@ -605,13 +608,12 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) unsigned long start =3D slot->gmem.pgoff; unsigned long end =3D start + slot->npages; struct kvm_gmem *gmem; - struct file *file; =20 /* * Nothing to do if the underlying file was already closed (or is being * closed right now), kvm_gmem_release() invalidates all bindings. */ - file =3D kvm_gmem_get_file(slot); + CLASS(gmem_get_file, file)(slot); if (!file) return; =20 @@ -626,8 +628,6 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) */ WRITE_ONCE(slot->gmem.file, NULL); filemap_invalidate_unlock(file->f_mapping); - - fput(file); } =20 /* Returns a locked folio on success. */ @@ -674,19 +674,17 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memo= ry_slot *slot, int *max_order) { pgoff_t index =3D kvm_gmem_get_index(slot, gfn); - struct file *file =3D kvm_gmem_get_file(slot); struct folio *folio; bool is_prepared =3D false; int r =3D 0; =20 + CLASS(gmem_get_file, file)(slot); if (!file) return -EFAULT; =20 folio =3D __kvm_gmem_get_pfn(file, slot, index, pfn, &is_prepared, max_or= der); - if (IS_ERR(folio)) { - r =3D PTR_ERR(folio); - goto out; - } + if (IS_ERR(folio)) + return PTR_ERR(folio); =20 if (!is_prepared) r =3D kvm_gmem_prepare_folio(kvm, slot, gfn, folio); @@ -698,8 +696,6 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory= _slot *slot, else folio_put(folio); =20 -out: - fput(file); return r; } EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn); @@ -708,7 +704,6 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn); long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src,= long npages, kvm_gmem_populate_cb post_populate, void *opaque) { - struct file *file; struct kvm_memory_slot *slot; void __user *p; =20 @@ -724,7 +719,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn= , void __user *src, long if (!kvm_slot_has_gmem(slot)) return -EINVAL; =20 - file =3D kvm_gmem_get_file(slot); + CLASS(gmem_get_file, file)(slot); if (!file) return -EFAULT; =20 @@ -782,7 +777,6 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn= , void __user *src, long =20 filemap_invalidate_unlock(file->f_mapping); =20 - fput(file); return ret && !i ? ret : i; } EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_populate); base-commit: 6b36119b94d0b2bb8cea9d512017efafd461d6ac --=20 2.51.0.710.ga91ca5db03-goog