Re: [PATCH v6 0/8] dma: swiotlb: Centralize default pool policy and sizing

[Marek Szyprowski]

On 24.09.2026 08:07, Aneesh Kumar K.V (Arm) wrote:
> This series centralizes swiotlb default-pool selection and sizing, and
> simplifies the initialization flags used to describe pool placement.
>
> The first patch replaces the addressing-limit argument with initialization
> flags and introduces explicit policies for the different reasons a default
> pool may be needed. Architectures now report DMA addressing constraints with
> SWIOTLB_INIT_ADDRESSING_LIMIT, while the core selects the corresponding pool
> policy.
>
> The second patch moves the reduced sizing used when the pool is needed only
> for unaligned kmalloc bouncing from arm64 and RISC-V into the swiotlb core.
>
> The third patch centralizes swiotlb sizing for memory-encrypted systems. It
> moves the existing x86 guest-sizing policy into the core. Host memory
> encryption retains the normal pool size, and a shared default pool is not
> selected solely for guest memory encryption when a restricted DMA pool is
> present.
>
> The fourth patch removes SWIOTLB_ANY. Pool placement is derived directly from
> SWIOTLB_INIT_ADDRESSING_LIMIT: pools required for limited DMA addressing are
> allocated below the architecture's low address limit, while other pools may
> be allocated anywhere in directly mapped memory. Xen continues to request a
> pool explicitly with SWIOTLB_INIT_REMAP without imposing a low-address
> constraint.


I would like to give this patchset some tests in linux-next and merge this to
v7.4-rc1, as this is important continuation of the code already merged to v7.3.


Any chance to get some more acks from arch maintainers (especially x86)?
Unfortunately I had to reduce the CC list due to my smtp limits...

> ...
>
>  Documentation/core-api/swiotlb.rst   |   8 +-
>  arch/arm/mm/init.c                   |   6 +-
>  arch/arm/xen/mm.c                    |   2 +-
>  arch/arm64/mm/init.c                 |  14 +-
>  arch/loongarch/kernel/setup.c        |   2 +-
>  arch/mips/cavium-octeon/dma-octeon.c |   2 +-
>  arch/mips/loongson64/dma.c           |   2 +-
>  arch/mips/sibyte/common/dma.c        |   2 +-
>  arch/powerpc/kernel/dma-swiotlb.c    |   4 +-
>  arch/powerpc/mm/mem.c                |  17 ++-
>  arch/powerpc/platforms/pseries/svm.c |  10 --
>  arch/powerpc/sysdev/fsl_pci.c        |   1 +
>  arch/riscv/mm/init.c                 |  24 +---
>  arch/s390/mm/init.c                  |   2 +-
>  arch/x86/include/asm/crash_reserve.h |   4 +-
>  arch/x86/kernel/pci-dma.c            |  23 +++-
>  arch/x86/mm/mem_encrypt.c            |  24 ----
>  include/linux/swiotlb.h              |  17 ++-
>  kernel/dma/swiotlb.c                 | 193 +++++++++++++++++++--------
>  19 files changed, 210 insertions(+), 147 deletions(-)

Best regards

-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland