| From | Thomas Gleixner <> | Subject | Re: [PATCHv6 24/30] x86/topology: Disable CPU online/offline control for TDX guests | Date | Thu, 17 Mar 2022 13:50:08 +0100 |
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On Wed, Mar 16 2022 at 05:08, Kirill A. Shutemov wrote: > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> > > Unlike regular VMs, TDX guests use the firmware hand-off wakeup method > to wake up the APs during the boot process. This wakeup model uses a > mailbox to communicate with firmware to bring up the APs. As per the > design, this mailbox can only be used once for the given AP, which means > after the APs are booted, the same mailbox cannot be used to > offline/online the given AP. More details about this requirement can be > found in Intel TDX Virtual Firmware Design Guide, sec titled "AP > initialization in OS" and in sec titled "Hotplug Device". > > Since the architecture does not support any method of offlining the > CPUs, disable CPU hotplug support in the kernel. > > Since this hotplug disable feature can be re-used by other VM guests, > add a new CC attribute CC_ATTR_HOTPLUG_DISABLED and use it to disable > the hotplug support. > > With hotplug disabled, /sys/devices/system/cpu/cpuX/online sysfs option > will not exist for TDX guests.
I can't find any code which removes the online file. The write will fail with -EOPNOTSUPP, right?
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> > Reviewed-by: Andi Kleen <ak@linux.intel.com> > Reviewed-by: Tony Luck <tony.luck@intel.com> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Other than that:
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
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