2024-03-25 15:24:37

by Jisheng Zhang

Subject: [PATCH v3 RESEND] riscv: mm: still create swiotlb buffer for kmalloc() bouncing if required

After commit f51f7a0fc2f4 ("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 <[email protected]>
Reviewed-by: Alexandre Ghiti <[email protected]>
---
since v2:
- rebase on v6.8-rc1
- collect Reviewed-by tag

since v1
- fix build error if CONFIG_RISCV_DMA_NONCOHERENT=n

arch/riscv/include/asm/cache.h | 2 +-
arch/riscv/mm/init.c | 16 +++++++++++++++-
2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/cache.h b/arch/riscv/include/asm/cache.h
index 2174fe7bac9a..570e9d8acad1 100644
--- a/arch/riscv/include/asm/cache.h
+++ b/arch/riscv/include/asm/cache.h
@@ -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)
{
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index fe8e159394d8..ac5e7f64c05c 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -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();
--
2.43.0

2024-04-28 22:01:09

by patchwork-bot+linux-riscv

Subject: Re: [PATCH v3 RESEND] riscv: mm: still create swiotlb buffer for kmalloc() bouncing if required

Hello:

This patch was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <[email protected]>:

On Mon, 25 Mar 2024 19:00:36 +0800 you wrote:
> After commit f51f7a0fc2f4 ("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.
>
> [...]

Here is the summary with links:
- [v3,RESEND] riscv: mm: still create swiotlb buffer for kmalloc() bouncing if required
https://git.kernel.org/riscv/c/fc7a50eed986

You are awesome, thank you!
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