new file mode 100644
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (c) 2024 NVIDIA Corporation & Affiliates */
+#ifndef LINUX_HMM_DMA_H
+#define LINUX_HMM_DMA_H
+
+#include <linux/dma-mapping.h>
+
+struct dma_iova_state;
+struct pci_p2pdma_map_state;
+
+/*
+ * struct hmm_dma_map - array of PFNs and DMA addresses
+ *
+ * @state: DMA IOVA state
+ * @pfns: array of PFNs
+ * @dma_list: array of DMA addresses
+ * @dma_entry_size: size of each DMA entry in the array
+ */
+struct hmm_dma_map {
+ struct dma_iova_state state;
+ unsigned long *pfn_list;
+ dma_addr_t *dma_list;
+ size_t dma_entry_size;
+};
+
+int hmm_dma_map_alloc(struct device *dev, struct hmm_dma_map *map,
+ size_t nr_entries, size_t dma_entry_size);
+void hmm_dma_map_free(struct device *dev, struct hmm_dma_map *map);
+dma_addr_t hmm_dma_map_pfn(struct device *dev, struct hmm_dma_map *map,
+ size_t idx, struct pci_p2pdma_map_state *p2pdma_state);
+bool hmm_dma_unmap_pfn(struct device *dev, struct hmm_dma_map *map, size_t idx);
+#endif /* LINUX_HMM_DMA_H */
@@ -23,6 +23,7 @@ struct mmu_interval_notifier;
* HMM_PFN_WRITE - if the page memory can be written to (requires HMM_PFN_VALID)
* HMM_PFN_ERROR - accessing the pfn is impossible and the device should
* fail. ie poisoned memory, special pages, no vma, etc
+ * HMM_PFN_P2PDMA_BUS - Bus mapped P2P transfer
* HMM_PFN_DMA_MAPPED - Flag preserved on input-to-output transformation
* to mark that page is already DMA mapped
*
@@ -40,6 +41,7 @@ enum hmm_pfn_flags {
HMM_PFN_ERROR = 1UL << (BITS_PER_LONG - 3),
/* Sticky flag, carried from Input to Output */
+ HMM_PFN_P2PDMA_BUS = 1UL << (BITS_PER_LONG - 6),
HMM_PFN_DMA_MAPPED = 1UL << (BITS_PER_LONG - 7),
HMM_PFN_ORDER_SHIFT = (BITS_PER_LONG - 8),
@@ -10,6 +10,7 @@
*/
#include <linux/pagewalk.h>
#include <linux/hmm.h>
+#include <linux/hmm-dma.h>
#include <linux/init.h>
#include <linux/rmap.h>
#include <linux/swap.h>
@@ -23,6 +24,7 @@
#include <linux/sched/mm.h>
#include <linux/jump_label.h>
#include <linux/dma-mapping.h>
+#include <linux/pci-p2pdma.h>
#include <linux/mmu_notifier.h>
#include <linux/memory_hotplug.h>
@@ -615,3 +617,198 @@ int hmm_range_fault(struct hmm_range *range)
return ret;
}
EXPORT_SYMBOL(hmm_range_fault);
+
+/**
+ * hmm_dma_map_alloc - Allocate HMM map structure
+ * @dev: device to allocate structure for
+ * @map: HMM map to allocate
+ * @nr_entries: number of entries in the map
+ * @dma_entry_size: size of the DMA entry in the map
+ *
+ * Allocate the HMM map structure and all the lists it contains.
+ * Return 0 on success, -ENOMEM on failure.
+ */
+int hmm_dma_map_alloc(struct device *dev, struct hmm_dma_map *map,
+ size_t nr_entries, size_t dma_entry_size)
+{
+ bool dma_need_sync = false;
+ bool use_iova;
+
+ if (!(nr_entries * PAGE_SIZE / dma_entry_size))
+ return -EINVAL;
+
+ /*
+ * The HMM API violates our normal DMA buffer ownership rules and can't
+ * transfer buffer ownership. The dma_addressing_limited() check is a
+ * best approximation to ensure no swiotlb buffering happens.
+ */
+ if (IS_ENABLED(CONFIG_DMA_NEED_SYNC))
+ dma_need_sync = !dev->dma_skip_sync;
+ if (dma_need_sync || dma_addressing_limited(dev))
+ return -EOPNOTSUPP;
+
+ map->dma_entry_size = dma_entry_size;
+ map->pfn_list =
+ kvcalloc(nr_entries, sizeof(*map->pfn_list), GFP_KERNEL);
+ if (!map->pfn_list)
+ return -ENOMEM;
+
+ use_iova = dma_iova_try_alloc(dev, &map->state, 0,
+ nr_entries * PAGE_SIZE);
+ if (!use_iova && dma_need_unmap(dev)) {
+ map->dma_list = kvcalloc(nr_entries, sizeof(*map->dma_list),
+ GFP_KERNEL);
+ if (!map->dma_list)
+ goto err_dma;
+ }
+ return 0;
+
+err_dma:
+ kfree(map->pfn_list);
+ return -ENOMEM;
+}
+EXPORT_SYMBOL_GPL(hmm_dma_map_alloc);
+
+/**
+ * hmm_dma_map_free - iFree HMM map structure
+ * @dev: device to free structure from
+ * @map: HMM map containing the various lists and state
+ *
+ * Free the HMM map structure and all the lists it contains.
+ */
+void hmm_dma_map_free(struct device *dev, struct hmm_dma_map *map)
+{
+ if (dma_use_iova(&map->state))
+ dma_iova_free(dev, &map->state);
+ kfree(map->pfn_list);
+ kfree(map->dma_list);
+}
+EXPORT_SYMBOL_GPL(hmm_dma_map_free);
+
+/**
+ * hmm_dma_map_pfn - Map a physical HMM page to DMA address
+ * @dev: Device to map the page for
+ * @map: HMM map
+ * @idx: Index into the PFN and dma address arrays
+ * @pci_p2pdma_map_state: PCI P2P state.
+ *
+ * dma_alloc_iova() allocates IOVA based on the size specified by their use in
+ * iova->size. Call this function after IOVA allocation to link whole @page
+ * to get the DMA address. Note that very first call to this function
+ * will have @offset set to 0 in the IOVA space allocated from
+ * dma_alloc_iova(). For subsequent calls to this function on same @iova,
+ * @offset needs to be advanced by the caller with the size of previous
+ * page that was linked + DMA address returned for the previous page that was
+ * linked by this function.
+ */
+dma_addr_t hmm_dma_map_pfn(struct device *dev, struct hmm_dma_map *map,
+ size_t idx, struct pci_p2pdma_map_state *p2pdma_state)
+{
+ struct dma_iova_state *state = &map->state;
+ dma_addr_t *dma_addrs = map->dma_list;
+ unsigned long *pfns = map->pfn_list;
+ struct page *page = hmm_pfn_to_page(pfns[idx]);
+ phys_addr_t paddr = hmm_pfn_to_phys(pfns[idx]);
+ size_t offset = idx * map->dma_entry_size;
+ dma_addr_t dma_addr;
+ int ret;
+
+ if ((pfns[idx] & HMM_PFN_DMA_MAPPED) &&
+ !(pfns[idx] & HMM_PFN_P2PDMA_BUS)) {
+ /*
+ * We are in this flow when there is a need to resync flags,
+ * for example when page was already linked in prefetch call
+ * with READ flag and now we need to add WRITE flag
+ *
+ * This page was already programmed to HW and we don't want/need
+ * to unlink and link it again just to resync flags.
+ */
+ if (dma_use_iova(state))
+ return state->addr + offset;
+
+ /*
+ * Without dma_need_unmap, the dma_addrs array is NULL, thus we
+ * need to regenerate the address below even if there already
+ * was a mapping. But !dma_need_unmap implies that the
+ * mapping stateless, so this is fine.
+ */
+ if (dma_need_unmap(dev))
+ return dma_addrs[idx];
+
+ /* Continue to remapping */
+ }
+
+ switch (pci_p2pdma_state(p2pdma_state, dev, page)) {
+ case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
+ case PCI_P2PDMA_MAP_NONE:
+ break;
+ case PCI_P2PDMA_MAP_BUS_ADDR:
+ dma_addr = pci_p2pdma_bus_addr_map(p2pdma_state, paddr);
+ pfns[idx] |= HMM_PFN_P2PDMA_BUS;
+ goto done;
+ default:
+ return DMA_MAPPING_ERROR;
+ }
+
+ if (dma_use_iova(state)) {
+ ret = dma_iova_link(dev, state, paddr, offset,
+ map->dma_entry_size, DMA_BIDIRECTIONAL, 0);
+ if (ret)
+ return DMA_MAPPING_ERROR;
+
+ ret = dma_iova_sync(dev, state, offset, map->dma_entry_size);
+ if (ret)
+ return DMA_MAPPING_ERROR;
+
+ dma_addr = state->addr + offset;
+ } else {
+ if (WARN_ON_ONCE(dma_need_unmap(dev) && !dma_addrs))
+ return DMA_MAPPING_ERROR;
+
+ dma_addr = dma_map_page(dev, page, 0, map->dma_entry_size,
+ DMA_BIDIRECTIONAL);
+ if (dma_mapping_error(dev, dma_addr))
+ return DMA_MAPPING_ERROR;
+
+ if (dma_need_unmap(dev))
+ dma_addrs[idx] = dma_addr;
+ }
+
+done:
+ pfns[idx] |= HMM_PFN_DMA_MAPPED;
+ return dma_addr;
+}
+EXPORT_SYMBOL_GPL(hmm_dma_map_pfn);
+
+/**
+ * hmm_dma_unmap_pfn - Unmap a physical HMM page from DMA address
+ * @dev: Device to unmap the page from
+ * @map: HMM map
+ * @idx: Index of the PFN to unmap
+ *
+ * Returns true if the PFN was mapped and has been unmapped, false otherwise.
+ */
+bool hmm_dma_unmap_pfn(struct device *dev, struct hmm_dma_map *map, size_t idx)
+{
+ struct dma_iova_state *state = &map->state;
+ dma_addr_t *dma_addrs = map->dma_list;
+ unsigned long *pfns = map->pfn_list;
+
+#define HMM_PFN_VALID_DMA (HMM_PFN_VALID | HMM_PFN_DMA_MAPPED)
+ if ((pfns[idx] & HMM_PFN_VALID_DMA) != HMM_PFN_VALID_DMA)
+ return false;
+#undef HMM_PFN_VALID_DMA
+
+ if (pfns[idx] & HMM_PFN_P2PDMA_BUS)
+ ; /* no need to unmap bus address P2P mappings */
+ else if (dma_use_iova(state))
+ dma_iova_unlink(dev, state, idx * map->dma_entry_size,
+ map->dma_entry_size, DMA_BIDIRECTIONAL, 0);
+ else if (dma_need_unmap(dev))
+ dma_unmap_page(dev, dma_addrs[idx], map->dma_entry_size,
+ DMA_BIDIRECTIONAL);
+
+ pfns[idx] &= ~(HMM_PFN_DMA_MAPPED | HMM_PFN_P2PDMA_BUS);
+ return true;
+}
+EXPORT_SYMBOL_GPL(hmm_dma_unmap_pfn);