Messages in this thread | | | Date | Wed, 28 Feb 2018 10:11:56 -0300 | From | Henrique de Moraes Holschuh <> | Subject | Re: [PATCH 4/7] x86/microcode: Do not upload microcode if CPUs are offline |
| |
On Wed, 28 Feb 2018, Borislav Petkov wrote: > Avoid loading microcode if any of the CPUs are offline, and issue a > warning. Having different microcode revisions on the system at any time > is outright dangerous.
Even if we update that microcode during CPU early bring-up, before we mark it on-line and start using it?
AFAIK, late-loading or not, this is what should happen in the current code: APs that are brought up after a microcode update is loaded (either by the early or late driver, it doesn't matter) will be always *early-updated* to the new microcode.
Is it dangerous to have an offline core at an older microcode revision than the online cores?
I am not against the patch, mind you, but I am curious about why it is supposed to be dangerous if we're updating the CPUs before we start using them *anyway*.
Also, if this is really dangerous, does it means safe CPU hotplug isn't possible? AFAICT, the firmware would have to do it for us, but it *doesn't* have the up-to-date microcode (*we* had to update it)...
-- Henrique Holschuh
| |