On 2022-11-06 22:01, Catalin Marinas wrote:
With all the infrastructure in place for bouncing small kmalloc()
buffers, add the corresponding Kconfig entry and select it for arm64.
AFAICS we're missing the crucial part to ensure that SWIOTLB is
available even when max_pfn <= arm64_dma_phys_limit, which is very
likely to be true on low-memory systems that care most about kmalloc
wastage. The only way to override that currently is with
"swiotlb=force", but bouncing *everything* is not desirable either.
Thanks,
Robin.
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
---
arch/arm64/Kconfig | 1 +
kernel/dma/Kconfig | 8 ++++++++
2 files changed, 9 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 3991cb7b8a33..f889cf16e6ab 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -100,6 +100,7 @@ config ARM64
select ARCH_WANT_FRAME_POINTERS
select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36)
select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
+ select ARCH_WANT_KMALLOC_DMA_BOUNCE
select ARCH_WANT_LD_ORPHAN_WARN
select ARCH_WANTS_NO_INSTR
select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index d6fab8e3cbae..b56e76371023 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -86,6 +86,14 @@ config SWIOTLB
bool
select NEED_DMA_MAP_STATE
+config ARCH_WANT_KMALLOC_DMA_BOUNCE
+ bool
+
+config DMA_BOUNCE_UNALIGNED_KMALLOC
+ def_bool y
+ depends on ARCH_WANT_KMALLOC_DMA_BOUNCE
+ depends on SWIOTLB && !SLOB
+
config DMA_RESTRICTED_POOL
bool "DMA Restricted Pool"
depends on OF && OF_RESERVED_MEM && SWIOTLB
