STRUCT SVM_RANGE(9)

💜 NAME 💜

struct svm_range — shared virtual memory range, bestie, and yes it's exactly as iconic as it sounds ✨

Okay so real talk, this page is from the Kernel API Manual (that's the manual name, told you I'd fold it in 🎀), and it's all about one struct. One struct! And she is the main character of shared virtual memory. Let's get into it.

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🌸 SYNOPSIS 🌸

So here's the whole glow-up, copied exactly, no cap:

struct svm_range {
    struct svm_range_list           *svms;
    struct mutex                    migrate_mutex;
    unsigned long                   start;
    unsigned long                   last;
    struct interval_tree_node       it_node;
    struct list_head                list;
    struct list_head                update_list;
    uint64_t npages;
    uint64_t vram_pages;
    dma_addr_t *dma_addr[MAX_GPU_INSTANCE];
    struct ttm_resource             *ttm_res;
    uint64_t offset;
    struct svm_range_bo             *svm_bo;
    struct list_head                svm_bo_list;
    struct mutex                    lock;
    unsigned int                    saved_flags;
    uint32_t flags;
    uint32_t preferred_loc;
    uint32_t prefetch_loc;
    uint32_t actual_loc;
    uint8_t granularity;
    atomic_t invalid;
    ktime_t validate_timestamp;
    struct mmu_interval_notifier    notifier;
    struct svm_work_list_item       work_item;
    struct list_head                deferred_list;
    struct list_head                child_list;
    unsigned long bitmap_access[BITS_TO_LONGS( MAX_GPU_INSTANCE)];
    unsigned long bitmap_aip[BITS_TO_LONGS( MAX_GPU_INSTANCE)];
    unsigned long bitmap_needs_unmap[BITS_TO_LONGS( MAX_GPU_INSTANCE)];
    unsigned long bitmap_mapped[BITS_TO_LONGS( MAX_GPU_INSTANCE)];
    bool mapping_done;
    atomic_t queue_refcount;
};

Like, look at her. Every single field accounted for, nothing skipped, we don't do that here 💅

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🦋 Members 🦋

Okay bestie, field-by-field tour, let's go 🫶

• svms — the list of svm ranges, and the structure itself is defined in kfd_process.
• migrate_mutex — the bouncer at the club 🚪: it serializes range migration, validation and mapping update so nobody's stepping on each other.
• start — range start address, in pages.
• last — range last address, in pages.
• it_node — the node [start, last] stored in the interval tree. start and last are page aligned, and the page size is (last - start + 1). Math is mathing ✨
• list — link list node, used to scan all ranges of svms.
• update_list — link list node used to add to update_list.
• npages — number of pages.
• vram_pages — the vram pages number in this svm_range.
• dma_addr — dma mapping address on each GPU for system memory physical page.
• ttm_res — vram ttm resource map.
• offset — range start offset within mm_nodes.
• svm_bo — struct to manage splited amdgpu_bo.
• svm_bo_list — link list node, to scan all ranges which share same svm_bo.
• lock — protects prange start, last, child_list, svm_bo_list. Yes, she's got a lock on those, it's giving responsible 🔒
• saved_flags — save/restore current PF_MEMALLOC flags.
• flags — flags defined as KFD_IOCTL_SVM_FLAG_*.
• actual_loc — this svm_range location. 0: all pages are from sys ram; GPU id: this svm_range may include vram pages from GPU with id actual_loc.
• granularity — migration granularity, log2 num pages.
• invalid — not 0 means cpu page table is invalidated. 😭
• validate_timestamp — system timestamp when range is validated.
• notifier — register mmu interval notifier.
• work_item — deferred work item information.
• deferred_list — list header used to add range to deferred list.
• child_list — list header for split ranges which are not added to svms yet.
• bitmap_access — index bitmap of GPUs which can access the range.
• bitmap_aip — index bitmap of GPUs which can access the range in place.
• bitmap_needs_unmap — index bitmap of GPUs which currently set NO_ACCESS.
• bitmap_mapped — index bitmap of GPUs which currently have the range mapped.
• mapping_done — true if range_validate_and_map complete successfully.
• queue_refcount — counted reference keeper for the queue, and honestly she's holding it down 💪

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✨ Description ✨

So what is she? 💖 struct svm_range is the data structure for a virtual memory range shared by CPU and GPUs. She can be allocated from system memory ram or device vram, and she can migrate — from ram to vram, or from vram to ram. Little globetrotter 🧚 No cap, that's the whole vibe.

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/gpu/drm/amd/amdkfd/kfd_svm.h

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Ok that's the whole page bestie, go forth and range responsibly 🍓

That's a wrap from ./drivers/gpu/drm/amd/amdkfd, dated October 2026 — this little manual page said what it said, periodt 👑💅