Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Michael Kelley <mikelley@microsoft.com>
To:     Wei Liu <wei.liu@kernel.org>,
        Linux on Hyper-V List <linux-hyperv@vger.kernel.org>
CC:     "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        Linux Kernel List <linux-kernel@vger.kernel.org>,
        Vineeth Pillai <viremana@linux.microsoft.com>,
        Sunil Muthuswamy <sunilmut@microsoft.com>,
        Nuno Das Neves <nunodasneves@linux.microsoft.com>,
        "pasha.tatashin@soleen.com" <pasha.tatashin@soleen.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: RE: [PATCH v5 05/16] clocksource/hyperv: use MSR-based access if
 running as root
Thread-Topic: [PATCH v5 05/16] clocksource/hyperv: use MSR-based access if
 running as root
Thread-Index: AQHW7yPzmjCK+zoGwESAxKKYTenmNao5F38w
Date:   Tue, 26 Jan 2021 00:34:26 +0000
Message-ID: <MWHPR21MB159358DEBC6EA386763B788FD7BC9@MWHPR21MB1593.namprd21.prod.outlook.com>
References: <20210120120058.29138-1-wei.liu@kernel.org>
 <20210120120058.29138-6-wei.liu@kernel.org>
In-Reply-To: <20210120120058.29138-6-wei.liu@kernel.org>
Accept-Language: en-US
Content-Language: en-US
msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=true;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_SetDate=2021-01-26T00:34:25Z;
 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_SiteId=72f988bf-86f1-41af-91ab-2d7cd011db47;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ActionId=7119e4ab-6e0f-41d5-b63e-ad573e340f96;
 MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_ContentBits=0
authentication-results: kernel.org; dkim=none (message not signed)
 header.d=none;kernel.org; dmarc=none action=none header.from=microsoft.com;
x-originating-ip: [66.75.126.197]
x-ms-publictraffictype: Email
x-ms-office365-filtering-ht: Tenant
x-ms-office365-filtering-correlation-id: 442de367-6917-4ebe-d832-08d8c192233c
x-ms-traffictypediagnostic: MW4PR21MB1875:
x-ms-exchange-transport-forked: True
x-microsoft-antispam-prvs: <MW4PR21MB18751E277E5CA22A95266CDCD7BC9@MW4PR21MB1875.namprd21.prod.outlook.com>
x-ms-oob-tlc-oobclassifiers: OLM:2887;
x-ms-exchange-senderadcheck: 1
x-microsoft-antispam: BCL:0;
x-microsoft-antispam-message-info: 9eSHzivG6DHnUDBHJ3IGOCIz+gA4t87ks1snlEc3Z4zojI7rRAG7qF/OM8URToZEbh06ZkLOv4gCob/NKjrVBeVdAgoXCsKPzOZi7pfDrlxojk+N2Y1y34dZu1MDF2UoP79nJo71bFn5kC9HZDdz1uecOxep9NyEl3ROTi7YTib1PgZojoBEbFm8jgqj+9FUTQFAr/Ri+HB3AERfKFt7CVh0vxUBt7u0nJeWYqEwph7k6XdnvBKv1/tED9auVR+SnXPx3nmkSNHY043zeyYCjw0MLKopP9j3L7v8V7Eue2svTqMQ71oG5GxuonUOhB2LP5xIajfPkf7u42/vir7kVgEgeq5AJ3XSieJHC/JfL0iVBbAqUUQeSJ5Mv8vd8E6EYtSQDm/kIgzlCw8iFlDin3n0aBgJp8rnjE8SC2n/uUrjJqxqJRUj5D5SsxUCj3bH4KUHakJNWVEOZIWH7MyGrX6XHN37cYxJ2DXKb4TK2rOlP14IggMzRfsLkfj2vkafkGVjpTgmo5Nn9MJSYUXIeg==
x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MWHPR21MB1593.namprd21.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(39860400002)(346002)(376002)(396003)(366004)(136003)(66946007)(66476007)(8676002)(9686003)(71200400001)(55016002)(76116006)(4326008)(86362001)(10290500003)(186003)(7696005)(478600001)(5660300002)(8936002)(52536014)(110136005)(66556008)(66446008)(2906002)(26005)(54906003)(316002)(6506007)(4744005)(64756008)(33656002)(82960400001)(82950400001)(83380400001)(8990500004);DIR:OUT;SFP:1102;
x-ms-exchange-antispam-messagedata: =?us-ascii?Q?wQemKI/4tKb9u1zqTTbe5QYDq6uRqFHLGMiiPNFfLN3sl7yaQa5LN/zR/irS?=
 =?us-ascii?Q?SWXp4MzBxt+bRAE+XmfBtC0YZnM3IuAjrd5ZtXp/YD2sLE41GdZ7aPPiLFE+?=
 =?us-ascii?Q?iB1cbKCxt5IxYWRUO5RP42Ec98S+4eH/ozWoXVllWJwZretvgnfe7IOD0+tq?=
 =?us-ascii?Q?guzpLsilvgf6nYQ2IxXmKX7m2ZCBdbiNLSyxmVahz39JHS29KIhJvXrYpDzy?=
 =?us-ascii?Q?wU01GHz1WAKCJg8sqKKI6Gqt2rXuqZJKw86lskNGipjn1yMjGDO2TnFVRumY?=
 =?us-ascii?Q?+nTrVYWSAT+tuWIBIj39r37hpXuGIkSF7ciZzjM47UfaxpXEE/ACK0ozVNFQ?=
 =?us-ascii?Q?G0jVG+rLxMS6NW0r2oGx/sc32tukjYzf1vXC/GassADror4JLvcW+rPYyoNu?=
 =?us-ascii?Q?fsK6TjMtzmy2vsiwDECSx3Er5BpVj1rl8Hbftik9sgMYbn1aU0zIoUzHbkus?=
 =?us-ascii?Q?5wzsShClWnqcJKgqWI0528wbuLDKKQf9uo9iFDrF2VhVl54/mjam5UxlCKnB?=
 =?us-ascii?Q?6JpOs5NFyVXslojuO3qRYeiuZqWVRpJYT0ti86Z6MLhYXOItTsqmQN8h7brc?=
 =?us-ascii?Q?89ZZy1ODRhDYmpgltviDEX8Jo529S5nRRctcSI/LLGOIaPqvdEpIMhJrWWlN?=
 =?us-ascii?Q?US7gTRmYcNTyPREBiyUpf+FUivV9yTFOpat5WXIM0li8TBKaqBOdLkR2NS28?=
 =?us-ascii?Q?XLJy7qxksvHrtni5BWpGHnRggscThSX41iRUnsfxwkKrGKr9+MVpVwfT1La/?=
 =?us-ascii?Q?enDRWISfju1Vr7aKFbXDJWwL1HVVjGx7xoCb9/a3XFD7bMimb57dnsLXwDL+?=
 =?us-ascii?Q?TlbJrjenywImEB40/5cnCR0fGd2mjkxSFJ3h9AwCF6K7RPH31Dtrnaq+/8Aa?=
 =?us-ascii?Q?IIZRDf6vZ6TQMCz/OCG7P+40lSH/sbcdojbOh9DZH+RXz8pvg50TqKE3pueJ?=
 =?us-ascii?Q?J1RHB1TyWDma3b5KFmki4nlH0jgv4qJvesD1Wv6Rppzw4N9qcL6zGk8T/1rC?=
 =?us-ascii?Q?5HSThhwZbt1WnHQw0NhefvCRB455+yvpgCLNLUSNpI2OCReFkhwq+oqjwqCC?=
 =?us-ascii?Q?Qj2fHq8x?=
Content-Type: text/plain; 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: 442de367-6917-4ebe-d832-08d8c192233c
X-MS-Exchange-CrossTenant-originalarrivaltime: 26 Jan 2021 00:34:27.1762
 (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: oJ8h1xody12mhY1M4Rg8Hre2DwtiggOGBLph2Oe7QZCLMSpNfMHwPUA9ZWG4JYSIwbWhxz5z6OnvhudxbO8oagWbhiFDLSVoo5OuXTpNSkY=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR21MB1875
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

From: Wei Liu <wei.liu@kernel.org> Sent: Wednesday, January 20, 2021 4:01 A=
M
>=20
> When Linux runs as the root partition, the setup required for TSC page
> is different. Luckily Linux also has access to the MSR based
> clocksource. We can just disable the TSC page clocksource if Linux is
> the root partition.
>=20
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
>  drivers/clocksource/hyperv_timer.c | 3 +++
>  1 file changed, 3 insertions(+)
>=20
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyp=
erv_timer.c
> index ba04cb381cd3..269a691bd2c4 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -426,6 +426,9 @@ static bool __init hv_init_tsc_clocksource(void)
>  	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
>  		return false;
>=20
> +	if (hv_root_partition)
> +		return false;
> +
>  	hv_read_reference_counter =3D read_hv_clock_tsc;
>  	phys_addr =3D virt_to_phys(hv_get_tsc_page());
>=20
> --
> 2.20.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>