Lines Matching +full:layer +full:- +full:primary

1 .. SPDX-License-Identifier: GPL-2.0
7 swiotlb is a memory buffer allocator used by the Linux kernel DMA layer. It is
10 the DMA layer calls swiotlb to allocate a temporary memory buffer that conforms
17 the DMA layer of the DMA attributes of the devices they are managing, and use
19 These APIs use the device DMA attributes and kernel-wide settings to determine
20 if bounce buffering is necessary. If so, the DMA layer manages the allocation,
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33 only provide 32-bit DMA addresses. By allocating bounce buffer memory below
40 directed to guest memory that is unencrypted. CoCo VMs set a kernel-wide option
43 the Linux kernel DMA layer does "sync" operations to cause the CPU to copy the
54 IOMMU access control is per-granule, the untrusted device can gain access to
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61 The primary swiotlb APIs are swiotlb_tbl_map_single() and
64 buffer memory is physically contiguous. The expectation is that the DMA layer
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89 pre-allocated at boot time (but see Dynamic swiotlb below). Because swiotlb
93 The need to pre-allocate the default swiotlb pool creates a boot-time tradeoff.
95 always be satisfied, as the non-blocking requirement means requests can't wait
97 this pre-allocated memory is not available for other uses in the system. The
109 must be limited to that 256 KiB. This value is communicated to higher-level
111 higher-level code fails to account for this limit, it may make requests that
118 min_align_mask is non-zero, it may produce an "alignment offset" in the address
124 swiotlb, max_sectors_kb will be 256 KiB. When min_align_mask is non-zero,
130 bounce buffer might start at a larger address if min_align_mask is non-zero.
131 Hence there may be pre-padding space that is allocated prior to the start of
133 alloc_align_mask boundary, potentially resulting in post-padding space. Any
134 pre-padding or post-padding space is not initialized by swiotlb code. The
136 devices. It is set to the granule size - 1 so that the bounce buffer is
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149 it works for devices that can only address 32-bits of physical memory (unless
150 architecture-specific code provides the SWIOTLB_ANY flag). In a CoCo VM, the
159 IO_TLB_SEGSIZE. Multiple smaller bounce buffers may co-exist in a single slot
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195 When CONFIG_SWIOTLB_DYNAMIC is enabled, swiotlb can do on-demand expansion of
208 background task can add another non-transient pool.
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237 swiotlb is managed with four primary data structures: io_tlb_mem, io_tlb_pool,
249 io_tlb_area describes an area. The primary field is the spin lock used to
251 entry for each area, and is accessed using a 0-based area index derived from the
299 requirements, it may allocate pre-padding space across zero or more slots. But
304 The "pad_slots" value is recorded only in the first non-padding slot allocated
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