fpstate_realloc(9)

💖 NAME 💖

okay bestie, this is fpstate_realloc(9) from the Kernel API Manual — and it is literally here to Reallocate struct fpstate for the requested new features. iconic behavior, no cap ✨

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🦋 SYNOPSIS 🦋

int fpstate_realloc (u64 xfeatures , unsigned int ksize , unsigned int
       usize , struct fpu_guest *guest_fpu );

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🎀 ARGUMENTS 🎀

• xfeatures — a bitmap of xstate features which extend the enabled features of that task. lowkey the feature wishlist 💅
• ksize — the required size for the kernel buffer. kernel-side room service 🫶
• usize — the required size for user space buffers. user-side space, slay 🌸
• guest_fpu — pointer to a guest FPU container. NULL for host allocations. yes, NULL is valid here, periodt 💜

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🌈 DESCRIPTION 🌈

okay so real talk — here's the note vs. vmalloc: if the task with a vzalloc-allocated buffer terminates quickly, vfree-induced IPIs may be a concern, but tasks with large states are likely to live longer. that's the whole vibe check, bestie 🧚

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⭐ RETURN ⭐

0 on success, -ENOMEM on allocation error. when it's 0 we celebrate; when it's -ENOMEM we cry a lil 😭

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👑 SEE ALSO 👑

• Kernel file ./arch/x86/kernel/fpu/xstate.c
• check_xtile_data_against_struct(9)
• __copy_xstate_to_uabi_buf(9)
• copy_xstate_to_uabi_buf(9)
• copy_uabi_to_xstate(9)
• xsaves(9)
• xrstors(9)
• fpu_xstate_prctl(9)

go read these too, iykyk 💖

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and that's the page, bestie 🎀 this cutie comes from ./arch/x86/kernel/fpu, dated October 2026, and it's literally fpstate_realloc(9) — byeee 💅✨