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
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!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
Hi Jisheng,
On Mon, Mar 25, 2024 at 12:15 PM Jisheng Zhang <[email protected]> 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.
>
> 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]>
Thanks for your patch, which is now commit fc7a50eed9860d4b ("riscv:
mm: still create swiotlb buffer for kmalloc() bouncing if required")
in riscv/for-next (next-20240429 and later).
On RZ/Five, which has 1 GiB of RAM, i.e. a bit less for free use:
Inode-cache hash table entries: 65536 (order: 7, 524288 bytes, linear)
Built 1 zonelists, mobility grouping on. Total pages: 225792
mem auto-init: stack:off, heap alloc:off, heap free:off
+software IO TLB: SWIOTLB bounce buffer size adjusted to 0MB
^^^
+software IO TLB: area num 1.
+software IO TLB: mapped [mem 0x000000007ef56000-0x000000007f056000] (1MB)
^^^
Virtual kernel memory layout:
I was a bit intrigued by the "0MB". However, that seems to be correct:
mem_init: memblock_phys_mem_size() = 939524096
mem_init: size = 917504
mem_init: swiotlb_size_or_default() = 67108864
and it must be rounded up to 1 MB later.
Apparently arm64 has the same discrepancy, which I never really noticed
before (and I have no arm64 platforms with 1 GiB RAM or less):
mem_init: memblock_phys_mem_size() = 2013265920
mem_init: size = 1966080
mem_init: swiotlb_size_or_default() = 67108864
software IO TLB: SWIOTLB bounce buffer size adjusted to 1MB
^^^
software IO TLB: area num 2.
software IO TLB: mapped [mem 0x00000000b9400000-0x00000000b9600000] (2MB)
^^^
> --- 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();
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68korg
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds