set_mtrr_state(9)

set_mtrr_state(9) 🎀

okay bestie, welcome to set_mtrr_state(9) from the Kernel API Manual — this is the little function that sets the MTRR state for this CPU, and we’re gonna read it together like a group chat 💅✨

💖 NAME 💖

set_mtrr_state — Set the MTRR state for this CPU. 🦋

✨ SYNOPSIS ✨

unsigned long set_mtrr_state (void );

🌸 ARGUMENTS 🌸

• void — no arguments, bestie. zero. none. the function is out here taking absolutely nothing and we love that for it 🫶

🚨 NOTE 🚨

okay so real talk: the CPU must already be in a safe state for MTRR changes, no cap. That includes measures that only a single CPU can be active in set_mtrr_state so it doesn’t get subject to races for usage of deftype_lo. This is accomplished by taking cache_disable_lock. 💀🔒

🔥 RETURN 🔥

• 0 if no changes made 😌
• else a mask indicating what was changed 👑

👀 SEE ALSO 👀

Kernel file ./arch/x86/kernel/cpu/mtrr/generic.c:

• guest_force_mtrr_state(9)
• mtrr_type_lookup(9)
• set_fixed_range(9)
• generic_get_free_region(9)
• set_fixed_ranges(9)
• generic_set_mtrr(9)

kiss kiss 💋 source/version: ./arch/x86/kernel/cpu/mtrr • date: October 2026 • and yes, it’s still set_mtrr_state(9) — iconic forever, periodt 🌈👑