pat_pfn_immune_to_uc_mtrr(9)

📦 version 7.3.1, in nixpkgs unstable

✨ pat_pfn_immune_to_uc_mtrr(9) ✨

okay so this is from the Kernel API Manual bestie, and it's literally one little function that answers one very specific question 🎀

🌸 NAME 🌸

pat_pfn_immune_to_uc_mtrr — the vibe check that tells you whether the PAT memory type of @pfn cannot be overridden by the UC MTRR memory type 💅

Like. It's asking "is this page frame immune or not" and honestly same.

🦋 SYNOPSIS 🦋

bool pat_pfn_immune_to_uc_mtrr (unsigned long pfn );

returns a bool, takes an unsigned long pfn, that's the whole thing, no cap ✨

🎀 ARGUMENTS 🎀

  • pfn — the page frame number you wanna check 🔍 that's it, that's the argument

💖 DESCRIPTION 💖

🚨 Only to be called when PAT is enabled. 🚨 like for real, don't come at it with PAT disabled, that's not the move 🙈

So here's the tea, bestie: it returns true if the PAT memory type of pfn is UC, UC-, or WC 👑

And it returns false in other cases. that's it. that's the function. iconic behaviour honestly 🫶

💅 SEE ALSO 💅

Kernel file ./arch/x86/mm/pat/memtype.c and its little friend group:

go read those next, iykyk 🌈

⭐ sign-off ⭐

mwah, that's the whole page 💜 it lives over in ./arch/x86/mm/pat and it's stamped October 2026, so mark your calendars bestie 🗓️✨

📦 where this page comes from