STRUCT IO_TLB_POOL(9)

💖 struct io_tlb_pool(9) 💖

okay bestie, buckle up — this is a page from the Kernel API Manual about struct io_tlb_pool, which is genuinely one of those "sounds scary, is actually just a fancy address book" situations. ngl the name is giving intimidating but we're gonna get through it together 🫶

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✨ NAME ✨

struct io_tlb_pool — the descriptor for an IO TLB memory pool 💅

Like, it's the little ID card that a swiotlb memory pool carries around so the kernel knows who it is. That's the vibe.

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🌸 SYNOPSIS 🌸

struct io_tlb_pool {
    phys_addr_t start;
    phys_addr_t end;
    void *vaddr;
    unsigned long nslabs;
    bool late_alloc;
    unsigned int nareas;
    unsigned int area_nslabs;
    struct io_tlb_area *areas;
    struct io_tlb_slot *slots;
  #ifdef CONFIG_SWIOTLB_DYNAMIC;
    struct list_head node;
    struct rcu_work dyn_free;
    bool transient;
    bool cc_shared;
  #endif;
 };

like look at her. so structured. so organized. main character energy fr fr 👑

heads up bestie — those last four fields only show up when CONFIG_SWIOTLB_DYNAMIC is defined. so it's a conditional slay 💀

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🎀 Members 🎀

• start — the start address of the swiotlb memory pool. it's used to do a quick range check, aka "wait, did this API actually allocate this memory or not?" a little vibe check for addresses ✨
• end — the end address of the swiotlb memory pool. same deal as start: quick range check to see if the memory was in fact allocated by this API. they're a matching set, iykyk 🦋
• vaddr — the virtual address of the swiotlb memory pool. here's the tea: the pool may get remapped in the memory encrypted case, and it stores this virtual address for bounce buffer operation. so she's flexible 💅
• nslabs — the number of IO TLB slots between start and end. for the default swiotlb, this can be adjusted with a boot parameter — see setup_io_tlb_npages. lowkey customizable 😌
• late_alloc — true if it was allocated using the page allocator. that's the whole description, she's short and sweet 🍓
• nareas — number of areas in the pool.
• area_nslabs — number of slots in each area.
• areas — array of memory area descriptors. plural. a whole squad 🌈
• slots — array of slot descriptors. also a squad, different squad 💜
• node — member of the IO TLB memory pool list. she's on the list, literally 😭
• dyn_free — an RCU work item used to free the pool from process context. the cleanup crew 🧹
• transient — true if transient memory pool. yes she's temporary, no she's not less iconic 💀
• cc_shared — true if the pool memory is shared for confidential computing. secretive but make it secure 🔥

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🦋 SEE ALSO 🦋

• Kernel file ./include/linux/swiotlb.h — struct io_tlb_mem(9), swiotlb_find_pool(9)

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okay go read those too, they're literally the friends of this struct and honestly the whole group chat is worth a look 👑

sign-off time: this masterpiece lives in ./include/linux, dated October 2026, and she answers to the name struct io_tlb_pool(9). periodt. 💖✨🎀