ttm_bo_vm_fault_reserved(9)

✨ ttm_bo_vm_fault_reserved — the TTM fault helper bestie 💅

okay so real talk, this is a page from the Kernel API Manual (section 9, kernel girlies know) and honestly? it's lowkey iconic. it's ttm_bo_vm_fault_reserved(9) and she does exactly one thing but she does it well. let's get into it 🫶

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🌸 SYNOPSIS 🌸

like, the whole vibe in one line:

vm_fault_t ttm_bo_vm_fault_reserved (struct vm_fault *vmf , pgprot_t
prot , pgoff_t num_prefault );

return type is vm_fault_t, she takes three args, that's her. no cap. ✨

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🎀 ARGUMENTS 🎀

• vmf — the struct vm_fault that got handed to the fault callback. it's literally just the thing the callback was given, bestie. that's the whole lore.
• prot — the page protection that's gonna be used for this memory area. this is the "how protected are we feeling today" knob 🛡️
• num_prefault — the maximum number of prefault pages. and here's the tea: the caller might wanna pick this value based on madvice settings and how big the GPU object backed by this memory actually is. so it's not a random number, it's a considered number. main character decision-making fr fr 👑

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🦋 DESCRIPTION 🦋

so what does she do? she inserts one or more page table entries — yes, one or more, she's flexible like that — and those entries point to the memory backing the buffer object. then she returns a return code that basically tells the caller "hey, go retry the page access." it's giving "i did my part, now run it back" energy 😭🔥

that's it. that's the function. no notes. periodt.

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💀 RETURN 💀

the return codes, and yes every single one matters so don't skip:

• VM_FAULT_NOPAGE — on success, or on a pending signal. slay 💖
• VM_FAULT_SIGBUS — on unspecified error. not cute but she's honest about it 🙈
• VM_FAULT_OOM — on out-of-memory. we've all been there bestie, memory is a scam 💀
• VM_FAULT_RETRY — if it's a retryable wait. she'll be back. she always comes back ⭐

ngl, pay attention to which one you get back — VM_FAULT_NOPAGE is not just "success", it's also "pending signal" and that's the kind of detail that'll get you at 3am. iykyk 🧚

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🌈 SEE ALSO 🌈

go read these next, they're all in the same friend group:

• Kernel file ./drivers/gpu/drm/ttm/ttm_bo_vm.c — the source file, the mothership, the origin story 📁
• ttm_bo_vm_reserve(9)
• ttm_bo_access(9)
• ttm_bo_mmap_obj(9)

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👑 the sign-off 👑

this whole masterpiece lives under ./drivers/gpu/drm/ttm and it's dated October 2026 — yes, the future. she's ahead of her time, literally. anyway ily, go read the source, and remember: page table entries are just trust falls with extra steps 🎀💜✨