Received-SPF: pass (google.com: domain of linux-kernel+bounces-98407-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
From: "Tian, Kevin" <kevin.tian@intel.com>
To: Alex Williamson <alex.williamson@redhat.com>
CC: "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "eric.auger@redhat.com"
	<eric.auger@redhat.com>, "clg@redhat.com" <clg@redhat.com>, "Chatre,
 Reinette" <reinette.chatre@intel.com>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>, "stable@vger.kernel.org"
	<stable@vger.kernel.org>
Subject: RE: [PATCH v2 6/7] vfio/platform: Create persistent IRQ handlers
Thread-Topic: [PATCH v2 6/7] vfio/platform: Create persistent IRQ handlers
Thread-Index: AQHaca1GPcQiX/X4gkacyzowtf1WV7ExywVw
Date: Mon, 11 Mar 2024 01:55:48 +0000
Message-ID: <BN9PR11MB527674AA4544E1FB82949FF68C242@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20240308230557.805580-1-alex.williamson@redhat.com>
 <20240308230557.805580-7-alex.williamson@redhat.com>
In-Reply-To: <20240308230557.805580-7-alex.williamson@redhat.com>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?3q9tIlVE7wQ0r74vEFisPHsldvd0hVN9aYIlyqrmS4aqKWU3CvORYBGFxe1c?=
 =?us-ascii?Q?CCYl0y11HWI+6V/fSp0OfDVzANOlmzp9K1YViWbazdwidUTj+QbVMqZ9K0cK?=
 =?us-ascii?Q?ijk2+OIdalD8RvCa604uf/H511AJ0CK4i581NGusrHzAT6ylW5J1FGv46S/6?=
 =?us-ascii?Q?mKt2hVAX8pdGinT0Vgc9eKCB9rUA10pp2m5kPjbphx/NWZa6v7elisr9N5yV?=
 =?us-ascii?Q?XRyU/z6h+bXDvl4RIvHPMnTpVm8lg02HIUpwzG3PDNkTJw8rPGquPVBZCH6K?=
 =?us-ascii?Q?qt2+EgYM/09Xq7X72D7H5Lla0fcjAX0xcDwaZNmnppNYk44ILyJKmFbDZzgE?=
 =?us-ascii?Q?6dM6i+wEexQKJQETwXnpXR4gDMxRvxd5MeQVArkqm5ZnYcjx2xvRBaHSw4wO?=
 =?us-ascii?Q?tdLyp75lmZ+bFKoZaM/+FA3xfbOt5n181DlqGPkzaTqS7BwcGel+rrVuipg5?=
 =?us-ascii?Q?0tzBOLig2uzlMSHhlivdWKHPEJAQ3xh4/caGWSzhoGBnBziehxKs6gQTJelz?=
 =?us-ascii?Q?Knvk14QB64AfE8Ti6opMmcbqvlG2b0aDQKZTyEZS9U8Cm0z54y78uZLeWxJH?=
 =?us-ascii?Q?izJqZQTk4kSEXWVaj8vQY5cBvA3uBSi83u4ZYhijwoi/g9kCebMghnStX1KJ?=
 =?us-ascii?Q?LluZH1roXVpAkUUWwtS4T2178YNU6+8ciyTHfGUAW4La6zbWhsTI5pOjvyn5?=
 =?us-ascii?Q?M/QqoLkG4bvRSxFpWS4wfKBpJx74NbcPkpdeZkpp/GhggzZIfk8j+kHPE+eK?=
 =?us-ascii?Q?q5Pp46R7I9mWKLjcac76+HG3wA7pm9Tw/zBB5KSbHTzg9ev7G/tv+8gkZYRo?=
 =?us-ascii?Q?FCC8JqvNxMRn74wuOkeuU8wH6mM4m/N3U6YzRYyFaTIPYTlSZfzETv/W8Da8?=
 =?us-ascii?Q?Ka2LwSGjT3+akV1L4dqC2YfDwy7ldWT7EEP8NYN/9uI1IF4CEmlyjAZPnxvf?=
 =?us-ascii?Q?8imL9Kd/fqqqg9t3F4kLAJ7V7dZjuBwOYOd8hm4Rl6fgjlbwpqebsbH7Ncy8?=
 =?us-ascii?Q?ygKqfIUz9k0r7uIcJOgvF56RHxfaajTIslc1aF5Ixff9+n4ZkEc8ry2avofJ?=
 =?us-ascii?Q?tlgJbyBaVAK69/Dotv+VRJARSPHGomOqZ9Y1pAC4+KcogERV3Rh4aFaJbTRn?=
 =?us-ascii?Q?zf3wzmTtVwJPiYJahmPWG8T6uiuqFTtDMk+w8puT3znJJwaHyskNGAopzxon?=
 =?us-ascii?Q?VjEeG0e2mXUlz2XKe5r9AUkO3rxqtpo8sL8RkBFF4JrF4M3XgCxsjBL97FKU?=
 =?us-ascii?Q?lE8LrHOKVQi7MEXBymPUcEHGM0c9VE1p+hVNX0AH4ViVvaxoih44a/jfZyzF?=
 =?us-ascii?Q?cBYc4n9ug+9dj+QzQXLnJS8553o50zTvpRZtUpkkvYGlnoDNtB0m+rFKKuHK?=
 =?us-ascii?Q?MkOnyMaIjVd+ThWl8K8gGTlMTlt/b2/vEZEGIVXsEIn7gXqPCS5PIIBsP4YJ?=
 =?us-ascii?Q?zwMIDMy51kUeTzaltrqtZbQH68S/3PaStCFwlUcAJZ0cRqW19gjXVnMiPQfH?=
 =?us-ascii?Q?T+rOq2wETm2EwwE6ttL+FqlY+hkjUB3wcpGN1hubffXSTMv3hdAVSv91eB+m?=
 =?us-ascii?Q?5B4yhWcIej1N8QUIV4LmyR53kkp4+2MtikY8TFN+?=
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk
X-Mailing-List: linux-kernel@vger.kernel.org
List-Id: <linux-kernel.vger.kernel.org>
List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org>
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: BN9PR11MB5276.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 9a1a1e9c-eb20-487c-db84-08dc416e5f9d
X-MS-Exchange-CrossTenant-originalarrivaltime: 11 Mar 2024 01:55:48.5831
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: oACKfTzF2zqD1JakUzw0z7/yHsgKrVEr9YLLMu190kALwy7uIrY9JJbXr6+OrtR6nmw7W8q14yx3BxAYPJdnZQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR11MB4719
X-OriginatorOrg: intel.com

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Saturday, March 9, 2024 7:05 AM
>=20
> The vfio-platform SET_IRQS ioctl currently allows loopback triggering of
> an interrupt before a signaling eventfd has been configured by the user,
> which thereby allows a NULL pointer dereference.
>=20
> Rather than register the IRQ relative to a valid trigger, register all
> IRQs in a disabled state in the device open path.  This allows mask
> operations on the IRQ to nest within the overall enable state governed
> by a valid eventfd signal.  This decouples @masked, protected by the
> @locked spinlock from @trigger, protected via the @igate mutex.
>=20
> In doing so, it's guaranteed that changes to @trigger cannot race the
> IRQ handlers because the IRQ handler is synchronously disabled before
> modifying the trigger, and loopback triggering of the IRQ via ioctl is
> safe due to serialization with trigger changes via igate.
>=20
> For compatibility, request_irq() failures are maintained to be local to
> the SET_IRQS ioctl rather than a fatal error in the open device path.
> This allows, for example, a userspace driver with polling mode support
> to continue to work regardless of moving the request_irq() call site.
> This necessarily blocks all SET_IRQS access to the failed index.
>=20
> Cc: Eric Auger <eric.auger@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: 57f972e2b341 ("vfio/platform: trigger an interrupt via eventfd")
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>