Messages in this thread | | | Date | Thu, 17 Mar 2022 23:47:44 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCHv6 24/30] x86/topology: Disable CPU online/offline control for TDX guests |
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On Thu, Mar 17, 2022 at 01:50:08PM +0100, Thomas Gleixner wrote: > 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?
Right. Will fix the commit message.
-- Kirill A. Shutemov
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