pt_compute_best_pgsize(9)

📦 version 7.3.1, in nixpkgs unstable

💅 pt_compute_best_pgsize(9) — a Kernel API Manual moment ✨

okay so bestie, we're diving into the kernel API manual and honestly this one is a little gem 🎀 it lives in the Kernel API Manual and it's about picking the perfect page size for leaf entries. yes, we're matchmaking addresses now, it's giving main character energy 👑

✨ NAME ✨

pt_compute_best_pgsize — Determine the best page size for leaf entries 🦋

like literally, it's the function that looks at your addresses and goes "this is the page size for you, bestie" 💖

🌸 SYNOPSIS 🌸

unsigned int pt_compute_best_pgsize (pt_vaddr_t pgsz_bitmap , pt_vaddr_t
va , pt_vaddr_t last_va , pt_oaddr_t oa );

that's the whole signature, no cap, copy it exactly if you're typing it out 🙈

🧚 ARGUMENTS 🧚

  • pgsz_bitmap — Permitted page sizes 💫 the little bitmap of what you're actually allowed to use, the vibe check for sizes
  • va — Starting virtual address for the leaf entry 🌈 like where the leaf entry begins on the virtual side
  • last_va — Last virtual address for the leaf entry, sets the max page size 🔥 it's the upper bound bestie, it literally caps how big you can go
  • oa — Starting output address for the leaf entry 💜 where the leaf entry starts on the output side

👑 DESCRIPTION 👑

So the whole gig: compute the largest page size for va, last_va, and oa together and return it in lg2 ✨

The largest page size depends on two things, and you gotta respect both:

  1. the format's supported page sizes at this level 🎀 (what the format will actually let you do)
  2. the relative alignment of the VA and OA addresses 🦋 (whether these two are lined up enough for it to work)

and here's the important bit, so listen up 🙈 — 0 means the OA cannot be stored with the provided pgsz_bitmap. like, zero is the "nope, can't do it with these sizes" answer. it's the "not me, not today" of return values 💀

💖 SEE ALSO 💖

Kernel file ./drivers/iommu/generic_pt/pt_iter.h and its little friend group 🫶:

iykyk, that's the whole squad 💅

aaaand that's the page!! 🌸 ily for reading all the way to the end, mwah 🫶 this iconic little number ships out of ./drivers/iommu/generic_pt, dated October 2026, and it answers to pt_compute_best_pgsize(9) — periodt 💜

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