Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:4 as permitted sender) client-ip=2620:137:e000::3:4;
Date:   Tue, 5 Dec 2023 10:52:27 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Yan Zhao <yan.y.zhao@intel.com>
Cc:     iommu@lists.linux.dev, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, alex.williamson@redhat.com,
        pbonzini@redhat.com, seanjc@google.com, joro@8bytes.org,
        will@kernel.org, robin.murphy@arm.com, kevin.tian@intel.com,
        baolu.lu@linux.intel.com, dwmw2@infradead.org, yi.l.liu@intel.com
Subject: Re: [RFC PATCH 11/42] iommu: Add new domain op cache_invalidate_kvm
Message-ID: <20231205145227.GD2787277@nvidia.com>
References: <20231202091211.13376-1-yan.y.zhao@intel.com>
 <20231202092041.14084-1-yan.y.zhao@intel.com>
 <20231204150945.GF1493156@nvidia.com>
 <ZW7F3AJZe7vrqzcy@yzhao56-desk.sh.intel.com>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <ZW7F3AJZe7vrqzcy@yzhao56-desk.sh.intel.com>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?uMeeGNQN0kN2uDcY+Uy3Zeuk0gl1h0ne++C4YYN5LVwFTrjtRTwWccnJ+CLa?=
 =?us-ascii?Q?NmbqWc5JwjMr1V8lLzriiUfqNCb1MLLRaGJUGGv9rHVaaO74xVzB7/whirdr?=
 =?us-ascii?Q?2cDaBqalE5M3wU8dQUT3VLVwMIuzbcoP5CUfuz06EWbKfMjzYFmHfMx5zZG0?=
 =?us-ascii?Q?4jI3zlHvdB/N2RWEY0ih66szolRtLhiNLFWZTO90aatEcMIWkypvWqVuKQrR?=
 =?us-ascii?Q?AuYw77h32a2zKSf1tykmIPGM/W3OSKEBjej3kpp5f4vju1d6/wyc2LfO9oA9?=
 =?us-ascii?Q?l7Lsm8tAuq7enFmYm4IybnzAKqhzVudom7xJJ8CigFxeQw0MCtgWvKitls0Z?=
 =?us-ascii?Q?oohG/nN0izrMeMidAA+E5asfj/1UVkq+JarZdbuGJpiDzxJVUfG2WYacyqqv?=
 =?us-ascii?Q?X5ExbmeFd035uC3IZ6w4Y8kvjrXx5gLqaiLVeHTS4l9V8yx5I2977TokwApe?=
 =?us-ascii?Q?VGNGmE/Ygpz/ZZOyiyK6ZvWhXnmZD1Erp2e0Wl35jHaiLuy6bni5Ycyn8Hs4?=
 =?us-ascii?Q?Vnlhxa36cqMYcJUDx6+h73BQzXvDxtw/C7Av4GHl3t0wmUs/H49yu04FgWPC?=
 =?us-ascii?Q?/d9Gqm8efJtJ7Fb6ofAc6kATqf4sFSp20TrBcSpLCsHx9hkDj1gY3gfXaoXe?=
 =?us-ascii?Q?RZaHDeHEhGuQJ2DkpWzTmTpG9ocpr1/bopOmKGA2Kcq71X6xmN5ouTHbOnHO?=
 =?us-ascii?Q?+TcFzVJyWLUQvWJbyEb1/RJpwt9pHOqiT3U1EWyc6wUEepDnAF8rp9sC2TBQ?=
 =?us-ascii?Q?yRNh/YhUxMLzviH3hl+USCFgp6LwuZoogfEu6XnjxPcTkzzq0loHxAg0/dwF?=
 =?us-ascii?Q?/DroEvIu8s+dcoN8u+D+4v6pcZHTpv5c7+K71M9yNehG0W3V4qreN/HNBs73?=
 =?us-ascii?Q?+BTbjzs+LFvvr6OEZVEZiwSreLAZWkgTxzgnborBy0eYoZ+QtiN9UCJEqg02?=
 =?us-ascii?Q?dEvmzdX7uHI4dr6ixT4xqdtd7KQEmhKXQ/xkoQRWDATKJyU55hgenRbIFfxM?=
 =?us-ascii?Q?E02wr2fRzqveX2xDQ7ETYUgarKHV60sAPY+lQ5buehtNHm0in5AhkiYvW1w9?=
 =?us-ascii?Q?GPgIWEfhecbRo9Q3ey7phZxzzoGyDKPZFOFjFniPWRewY6mi2dQ51nRQLejM?=
 =?us-ascii?Q?Leqt1w7QispYclSPHHj0ZcPjoTe4+Il47wo0vA4iv6Xsvn7t/jFrbbaHOmWZ?=
 =?us-ascii?Q?KlHAQkiXhzfCP5GGXYRZ9dM+inf4Y98YaTRnB05jvzytnv4KecgtKflYQtp4?=
 =?us-ascii?Q?/fDAhD2rlDD5jSig/WmPGWLEQjuw4NF5HqSZzRmcNa0ie3OhLu8/rvO1vrv8?=
 =?us-ascii?Q?lb3opEUmDBe45W/GAnVQAVfl/P+K0uja7dnLVfl8FVlJT1yAVwV7xcBeya9u?=
 =?us-ascii?Q?yM+TrPhpA7BUNEZu7xAQLnq3eGSX4p5xnbkQ1jEbtNrwZahcAxoiiPwVAksz?=
 =?us-ascii?Q?ZWkzJIaCJWmX13F/1M2wnVv4YscFbw3oSTW6Y2voeBiDnFAuYkoBw7mqwb+s?=
 =?us-ascii?Q?gnKWH3BnNtFyD4Hf00CoizS8bmBUQ/uQSbcXjNCROyC0tJUJ4HYLlYPSqdHb?=
 =?us-ascii?Q?zmkkM96e7Ck6DJFrB5D+FO0KJ9pjLit6gnW0sP1d?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: aa60f102-1b1c-40eb-a680-08dbf5a1cd0f
X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Dec 2023 14:52:28.3456
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: Sn/nwmoAHaoVN8KhXSZZqDhGM7IXEzOyKixmxZp6lc7bNOTSyq2qLf4mYPGP+558
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4169
X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE
	autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on howler.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (howler.vger.email [0.0.0.0]); Tue, 05 Dec 2023 06:52:41 -0800 (PST)

On Tue, Dec 05, 2023 at 02:40:28PM +0800, Yan Zhao wrote:
> On Mon, Dec 04, 2023 at 11:09:45AM -0400, Jason Gunthorpe wrote:
> > On Sat, Dec 02, 2023 at 05:20:41PM +0800, Yan Zhao wrote:
> > > On KVM invalidates mappings that are shared to IOMMU stage 2 paging
> > > structures, IOMMU driver needs to invalidate hardware TLBs accordingly.
> > > 
> > > The new op cache_invalidate_kvm is called from IOMMUFD to invalidate
> > > hardware TLBs upon receiving invalidation notifications from KVM.
> > 
> > Why?
> > 
> > SVA hooks the invalidation directly to the mm, shouldn't KVM also hook
> > the invalidation directly from the kvm? Why do we need to call a chain
> > of function pointers? iommufd isn't adding any value in the chain
> > here.
> Do you prefer IOMMU vendor driver to register as importer to KVM directly?
> Then IOMMUFD just passes "struct kvm_tdp_fd" to IOMMU vendor driver for domain
> creation.

Yes, this is what we did for SVA

Function pointers are slow these days, so it is preferred to go
directly.

Jason