Re: [PATCH v8 03/20] KVM: x86: Support APX state for XSAVE ABI

[Chang S. Bae]

On 11/5/2026 9:46 PM, Jim Mattson wrote:
> Look at the lines immediately preceding the ones you quoted in
> copy_uabi_to_xstate():
>
>      /*
>       * The state that came in from userspace was user-state only.
>       * Mask all the user states out of 'xfeatures':
>       */
>      xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR_ALL;
>
>      /*
>       * Add back in the features that came in from userspace:
>       */
>      xsave->header.xfeatures |= hdr.xfeatures;
>
> All user-state bits in xsave->header.xfeatures are cleared before
> hdr.xfeatures is ORed in. If userspace clears bit i for any user state
> component in hdr.xfeatures, bit i in xsave->header.xfeatures is cleared,
> and the component is reset to its initial state.

Ah, right. Looks like sticking to what I thought before...