On Wed, Aug 25 2021 at 08:53, Chang S. Bae wrote:
> +/**
> + * struct fpu_xstate_buffer_config - xstate buffer configuration
> + * @max_size: The CPUID-enumerated all-feature "maximum" size
> + * for xstate per-task buffer.
> + * @min_size: The size to fit into the statically-allocated
> + * buffer. With dynamic states, this buffer no longer
> + * contains all the enabled state components.
> + * @user_size: The size of user-space buffer for signal and
> + * ptrace frames, in the non-compacted format.
> + */
> void fpstate_init(struct fpu *fpu)
> {
> union fpregs_state *state;
> + unsigned int size;
> + u64 mask;
>
> - if (likely(fpu))
> + if (likely(fpu)) {
> state = &fpu->state;
> - else
> + /* The dynamic user states are not prepared yet. */
> + mask = xfeatures_mask_all & ~xfeatures_mask_user_dynamic;
The patch ordering is really odd. Why aren't you adding
fpu->state_mask
and
fpu->state_size
first and initialize state_mask and state_size to the fixed mode and
then add the dynamic sizing on top?
> /*
> * If the target FPU state is not resident in the CPU registers, just
> * memcpy() from current, else save CPU state directly to the target.
> + *
> + * KVM does not support dynamic user states yet. Assume the buffer
> + * always has the minimum size.
> */
> if (test_thread_flag(TIF_NEED_FPU_LOAD))
> memcpy(&fpu->state, ¤t->thread.fpu.state,
> - fpu_kernel_xstate_size);
> + fpu_buf_cfg.min_size);
Which completely avoids the export of fpu_buf_cfg for KVM because the
information is just available via struc fpu. As a bonus the export of
fpu_kernel_xstate_size can be removed as well.
Hmm?
Thanks,
tglx
