Messages in this thread | | | From | Thomas Gleixner <> | Subject | RE: [patch 4/6] x86/fpu: Add guest support to xfd_enable_feature() | Date | Wed, 15 Dec 2021 10:53:04 +0100 |
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On Wed, Dec 15 2021 at 05:46, Kevin Tian wrote: >> From: Thomas Gleixner <tglx@linutronix.de> >> + if (guest_fpu) { >> + newfps->is_guest = true; >> + newfps->is_confidential = curfps->is_confidential; >> + newfps->in_use = curfps->in_use; > > What is the purpose of this 'in_use' field? Currently it's only > touched in three places: > > - set when entering guest; > - cleared when exiting to userspace; > - checked when freeing a guest FPU; > > The last one can be easily checked by comparing to current fps.
I added it for paranoia sake because the destruction of the KVM FPU state is not necessarily in the context of the vCPU thread. Yes, it should not happen...
>> + if (guest_fpu) { >> + curfps = xchg(&guest_fpu->fpstate, newfps); > > This can be a direct value update to guest_fpu->fpstate since > curfps has already been acquired in the start.
Indeed.
Thanks,
tglx
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