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authorPetr Tesarik <petr.tesarik.ext@huawei.com>2023-08-01 08:24:00 +0200
committerChristoph Hellwig <hch@lst.de>2023-08-01 18:02:17 +0200
commit62708b2ba4055cad43a95754e939566b56dde5b6 (patch)
tree1751603289119e9a0ccc5b25ef6820630c419abb /kernel/dma/Kconfig
parent158dbe9c9a3d36da824139e5304169326550c6c9 (diff)
swiotlb: add a flag whether SWIOTLB is allowed to grow
Add a config option (CONFIG_SWIOTLB_DYNAMIC) to enable or disable dynamic allocation of additional bounce buffers. If this option is set, mark the default SWIOTLB as able to grow and restricted DMA pools as unable. However, if the address of the default memory pool is explicitly queried, make the default SWIOTLB also unable to grow. This is currently used to set up PCI BAR movable regions on some Octeon MIPS boards which may not be able to use a SWIOTLB pool elsewhere in physical memory. See octeon_pci_setup() for more details. If a remap function is specified, it must be also called on any dynamically allocated pools, but there are some issues: - The remap function may block, so it should not be called from an atomic context. - There is no corresponding unremap() function if the memory pool is freed. - The only in-tree implementation (xen_swiotlb_fixup) requires that the number of slots in the memory pool is a multiple of SWIOTLB_SEGSIZE. Keep it simple for now and disable growing the SWIOTLB if a remap function was specified. Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'kernel/dma/Kconfig')
-rw-r--r--kernel/dma/Kconfig13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 562463fe30ea..4c1e9a3c0ab6 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -90,6 +90,19 @@ config SWIOTLB
bool
select NEED_DMA_MAP_STATE
+config SWIOTLB_DYNAMIC
+ bool "Dynamic allocation of DMA bounce buffers"
+ default n
+ depends on SWIOTLB
+ help
+ This enables dynamic resizing of the software IO TLB. The kernel
+ starts with one memory pool at boot and it will allocate additional
+ pools as needed. To reduce run-time kernel memory requirements, you
+ may have to specify a smaller size of the initial pool using
+ "swiotlb=" on the kernel command line.
+
+ If unsure, say N.
+
config DMA_BOUNCE_UNALIGNED_KMALLOC
bool
depends on SWIOTLB