On 3/7/25 08:41, Chao Gao wrote: > From: Yang Weijiang <weijiang.yang@xxxxxxxxx> > > To support CET virtualization, KVM needs the kernel to save/restore CET > supervisor xstate in guest FPUs when switching between guest and host > FPUs. > > Add CET supervisor xstate (i.e., XFEATURE_CET_KERNEL) support. Both the > guest FPU and the kernel FPU will allocate memory for the new xstate. > For the guest FPU, the xstate remains unused until the upcoming CET > virtualization is added to KVM. For the kernel FPU, the xstate is unused > until CET_S is enabled within the kernel. > > Note CET_S may or may not be enabled within the kernel, so always > allocating memory for XFEATURE_CET_KERNEL could potentially waste some > XSAVE buffer space. If necessary, this issue can be addressed by making > XFEATURE_CET_KERNEL a guest-only feature. I feel like these changelogs are long but say very little. This patch *WASTES* resources. Granted, it's only for a single patch, but it's totally not obvious. Could you work on tightening down the changelog, please? > --- a/arch/x86/kernel/fpu/xstate.c > +++ b/arch/x86/kernel/fpu/xstate.c > @@ -55,7 +55,7 @@ static const char *xfeature_names[] = > "Protection Keys User registers", > "PASID state", > "Control-flow User registers", > - "Control-flow Kernel registers (unused)", > + "Control-flow Kernel registers", This should probably be: > + "Control-flow Kernel registers (KVM only)", or something similar for now. XFEATURE_CET_KERNEL is *VERY* different from all of the other features and it's silly to pretend that it's the same.
