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X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR03MB5513 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/08/2023 8:01 am, Josh Poimboeuf wrote: > To support live migration, the hypervisor sets the "lowest common > denominator" of features. Probing the microcode isn't allowed because > any detected features might go away after a migration. > > As Andy Cooper states: > > "Linux must not probe microcode when virtualised.  What it may see > instantaneously on boot (owing to MSR_PRED_CMD being fully passed > through) is not accurate for the lifetime of the VM." > > Rely on the hypervisor to set the needed IBPB_BRTYPE and SBPB bits. > > Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support") > Suggested-by: Andrew Cooper > Signed-off-by: Josh Poimboeuf Reviewed-by: Andrew Cooper Thankyou for doing this patch.