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Thu, 27 Jan 2022 21:22:34 +0000 Received: from MWHPR21MB1593.namprd21.prod.outlook.com ([fe80::61d3:a4c2:9674:9db6]) by MWHPR21MB1593.namprd21.prod.outlook.com ([fe80::61d3:a4c2:9674:9db6%7]) with mapi id 15.20.4951.003; Thu, 27 Jan 2022 21:22:34 +0000 From: "Michael Kelley (LINUX)" To: Yanming Liu CC: Wei Liu , Andrea Parri , "linux-hyperv@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linux-fbdev@vger.kernel.org" , KY Srinivasan , Haiyang Zhang , Stephen Hemminger , Dexuan Cui , "drawat.floss@gmail.com" , "airlied@linux.ie" , "daniel@ffwll.ch" , "lkmlabelt@gmail.com" Subject: RE: [PATCH v2] hv: account for packet descriptor in maximum packet size Thread-Topic: [PATCH v2] hv: account for packet descriptor in maximum packet size Thread-Index: AQHYBbs9Z9MCDPVXTEy3Gdtosh0+p6xi6g+AgAe+98CAAC2igIAMpPbQ Date: Thu, 27 Jan 2022 21:22:34 +0000 Message-ID: References: <20220109095516.3250392-1-yanminglr@gmail.com> <20220110004419.GA435914@anparri> <20220114191307.uu2oel7wbxhiqe56@liuwe-devbox-debian-v2> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=ea6c9051-7354-494a-bc5c-30b630d3e7a6;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ContentBits=0;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=true;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Method=Standard;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Name=Internal;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2022-01-27T21:19:17Z;MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: MWHPR21MB1593.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: de5696b3-a466-454b-ba73-08d9e1db2282 X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Jan 2022 21:22:34.0416 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Mpdy78zrxXvjQanDD0zhI4401E7GKpe+DWJkd1pNCg6tzZ8kDpi9Y6GoswSbUcTq/GWjrZACZYnIQ91eMOgdYLLoBLogzOBgg8pJbxqnKjw= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR21MB1944 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yanming Liu Sent: Wednesday, January 19, 2022 1= 2:14 PM >=20 > On Thu, Jan 20, 2022 at 2:12 AM Michael Kelley (LINUX) > wrote: > > > > From: Wei Liu Sent: Friday, January 14, 2022 11:13= AM > > > > > > On Mon, Jan 10, 2022 at 01:44:19AM +0100, Andrea Parri wrote: > > > > (Extending Cc: list,) > > > > > > > > On Sun, Jan 09, 2022 at 05:55:16PM +0800, Yanming Liu wrote: > > > > The VSS driver in hv_snapshot.c allocates a receive buffer of 8 Kbytes > > and sets max_pkt_size to 8 Kbytes. But the received messages are > > all fixed size and small. I don't know why the driver uses an 8 Kbyte > > receive buffer instead of 4 Kbytes, but the current settings are > > more than sufficient. > > >=20 > Well, I'm not sure, on August 2021 there was a patch changing > max_pkt_size to 8 KiB for VSS driver: > https://lore.kernel.org/linux-hyperv/20210825190217.qh2c6yq5qr3ntum5@liuw= e-devbox-debian-v2/T/ >=20 > The patch mentioned a 6304 bytes VSS message. Which is part of the > reason I tried to address the more "general" problem of potentially > mismatching buffer size. >=20 This is certainly interesting. The Linux driver is not processing all those bytes, so I'm not sure what Hyper-V is passing to the guest. I'll check with the Hyper-V team to be sure. 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Thu, 27 Jan 2022 21:22:34 +0000 Received: from MWHPR21MB1593.namprd21.prod.outlook.com ([fe80::61d3:a4c2:9674:9db6]) by MWHPR21MB1593.namprd21.prod.outlook.com ([fe80::61d3:a4c2:9674:9db6%7]) with mapi id 15.20.4951.003; Thu, 27 Jan 2022 21:22:34 +0000 From: "Michael Kelley (LINUX)" To: Yanming Liu Subject: RE: [PATCH v2] hv: account for packet descriptor in maximum packet size Thread-Topic: [PATCH v2] hv: account for packet descriptor in maximum packet size Thread-Index: AQHYBbs9Z9MCDPVXTEy3Gdtosh0+p6xi6g+AgAe+98CAAC2igIAMpPbQ Date: Thu, 27 Jan 2022 21:22:34 +0000 Message-ID: References: <20220109095516.3250392-1-yanminglr@gmail.com> <20220110004419.GA435914@anparri> <20220114191307.uu2oel7wbxhiqe56@liuwe-devbox-debian-v2> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=ea6c9051-7354-494a-bc5c-30b630d3e7a6; MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ContentBits=0; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: MWHPR21MB1593.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: de5696b3-a466-454b-ba73-08d9e1db2282 X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Jan 2022 21:22:34.0416 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: Mpdy78zrxXvjQanDD0zhI4401E7GKpe+DWJkd1pNCg6tzZ8kDpi9Y6GoswSbUcTq/GWjrZACZYnIQ91eMOgdYLLoBLogzOBgg8pJbxqnKjw= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR21MB1944 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrea Parri , Wei Liu , Stephen Hemminger , "lkmlabelt@gmail.com" , "linux-hyperv@vger.kernel.org" , "airlied@linux.ie" , Haiyang Zhang , Dexuan Cui , "linux-fbdev@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , "drawat.floss@gmail.com" , KY Srinivasan Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" From: Yanming Liu Sent: Wednesday, January 19, 2022 1= 2:14 PM >=20 > On Thu, Jan 20, 2022 at 2:12 AM Michael Kelley (LINUX) > wrote: > > > > From: Wei Liu Sent: Friday, January 14, 2022 11:13= AM > > > > > > On Mon, Jan 10, 2022 at 01:44:19AM +0100, Andrea Parri wrote: > > > > (Extending Cc: list,) > > > > > > > > On Sun, Jan 09, 2022 at 05:55:16PM +0800, Yanming Liu wrote: > > > > The VSS driver in hv_snapshot.c allocates a receive buffer of 8 Kbytes > > and sets max_pkt_size to 8 Kbytes. But the received messages are > > all fixed size and small. I don't know why the driver uses an 8 Kbyte > > receive buffer instead of 4 Kbytes, but the current settings are > > more than sufficient. > > >=20 > Well, I'm not sure, on August 2021 there was a patch changing > max_pkt_size to 8 KiB for VSS driver: > https://lore.kernel.org/linux-hyperv/20210825190217.qh2c6yq5qr3ntum5@liuw= e-devbox-debian-v2/T/ >=20 > The patch mentioned a 6304 bytes VSS message. Which is part of the > reason I tried to address the more "general" problem of potentially > mismatching buffer size. >=20 This is certainly interesting. The Linux driver is not processing all those bytes, so I'm not sure what Hyper-V is passing to the guest. I'll check with the Hyper-V team to be sure. Michael