On Tue, 2023-11-28 at 14:58 +0000, Edgecombe, Rick P wrote: > On Fri, 2023-11-24 at 00:53 -0500, Yang Weijiang wrote: > > + /* > > + * Set guest's __user_state_size to fpu_user_cfg.default_size > > so that > > + * existing uAPIs can still work. > > + */ > > + fpu->guest_perm.__user_state_size = > > fpu_user_cfg.default_size; > > It seems like an appropriate value, but where does this come into play > exactly for guest FPUs? It is used because permission API is used for guest fpu state as well (for user features), and it affects two things: 1. If permission is not asked, then KVM will fail to resize the FPU state to match guest CPUID. 2. It will affect output size of the KVM_GET_XSAVE2 ioctl, which outputs buffer similar to other FPU state buffers exposed to userspace (like one saved on signal stack, or one obtained via ptrace). Best regards, Maxim Levitsky
