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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SA1PR11MB6734.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 74607d90-686e-44f7-084c-08db299e7353 X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Mar 2023 23:54:31.8825 (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: mGD2hFTuT2yi+XC2WR5lS9RCQqfOzDJuVM8calHDNHypTXjdjrLLx8It/fnSXtxbpwZEcnFGm4IA4wxIdQhEKw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR11MB4518 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > - if (cpu_feature_enabled(X86_FEATURE_XENPV)) > > + if (cpu_feature_enabled(X86_FEATURE_FRED)) { > > + /* > > + * Will use WRMSRNS/WRMSRLIST for performance once it's > upstreamed. > > + */ > > + wrmsrl(MSR_IA32_FRED_RSP0, > > + task_top_of_stack(task) + > TOP_OF_KERNEL_STACK_PADDING); > > + } else if (cpu_feature_enabled(X86_FEATURE_XENPV)) { >=20 > Whee, so hardware will really only ever look at this when RSP0? I don't n= eed to > worry about exceptions during context switch? You're right, we don't. RSP0 is only used in ring3. Exceptions from ring0 just keep using the curre= nt kernel stack unless a higher stack level needs to be used, e.g., RSP3 for #= DF. Thanks! Xin