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riscv: mm: still create swiotlb buffer for kmalloc() bouncing if required

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After commit f51f7a0fc2 ("riscv: enable DMA_BOUNCE_UNALIGNED_KMALLOC
for !dma_coherent"), for non-coherent platforms with less than 4GB
memory, we rely on users to pass "swiotlb=mmnn,force" kernel parameters
to enable DMA bouncing for unaligned kmalloc() buffers. Now let's go
further: If no bouncing needed for ZONE_DMA, let kernel automatically
allocate 1MB swiotlb buffer per 1GB of RAM for kmalloc() bouncing on
non-coherent platforms, so that no need to pass "swiotlb=mmnn,force"
any more.

The math of "1MB swiotlb buffer per 1GB of RAM for kmalloc() bouncing"
is taken from arm64. Users can still force smaller swiotlb buffer by
passing "swiotlb=mmnn".

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240325110036.1564-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Jisheng Zhang 2024-03-25 19:00:36 +08:00 committed by Palmer Dabbelt
parent 0fdbb06379
commit dcb2743d1e
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
2 changed files with 16 additions and 2 deletions
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2
arch/riscv/include/asm/cache.h
View File

@ -26,8 +26,8 @@
#ifndef __ASSEMBLY__
#ifdef CONFIG_RISCV_DMA_NONCOHERENT
extern int dma_cache_alignment;
#ifdef CONFIG_RISCV_DMA_NONCOHERENT
#define dma_get_cache_alignment dma_get_cache_alignment
static inline int dma_get_cache_alignment(void)
{

16
arch/riscv/mm/init.c
View File

@ -161,11 +161,25 @@ static void print_vm_layout(void) { }
void __init mem_init(void)
{
bool swiotlb = max_pfn > PFN_DOWN(dma32_phys_limit);
#ifdef CONFIG_FLATMEM
BUG_ON(!mem_map);
#endif /* CONFIG_FLATMEM */
swiotlb_init(max_pfn > PFN_DOWN(dma32_phys_limit), SWIOTLB_VERBOSE);
if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb &&
dma_cache_alignment != 1) {
/*
* If no bouncing needed for ZONE_DMA, allocate 1MB swiotlb
* buffer per 1GB of RAM for kmalloc() bouncing on
* non-coherent platforms.
*/
unsigned long size =
DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
swiotlb = true;
}
swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
memblock_free_all();
print_vm_layout();