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    SubjectRe: [PATCH v2 08/14] arm64: Enforce bounce buffers for realm DMA
    On Fri, Apr 12, 2024 at 09:42:07AM +0100, Steven Price wrote:
    > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
    > index 786fd6ce5f17..01a2e3ce6921 100644
    > --- a/arch/arm64/mm/init.c
    > +++ b/arch/arm64/mm/init.c
    > @@ -370,7 +370,9 @@ void __init bootmem_init(void)
    > */
    > void __init mem_init(void)
    > {
    > - bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
    > + bool swiotlb = (max_pfn > PFN_DOWN(arm64_dma_phys_limit));

    This series tends to add unnecessary brackets.

    > +
    > + swiotlb |= is_realm_world();

    I first thought we wouldn't need this, just passing 'true' further down
    but I guess you want to avoid reducing the bounce buffer size when it's
    only needed for kmalloc() bouncing.

    >
    > if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
    > /*
    > @@ -383,7 +385,12 @@ void __init mem_init(void)
    > swiotlb = true;
    > }
    >
    > - swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
    > + if (is_realm_world()) {
    > + swiotlb_init(swiotlb, SWIOTLB_VERBOSE | SWIOTLB_FORCE);
    > + swiotlb_update_mem_attributes();
    > + } else {
    > + swiotlb_init(swiotlb, SWIOTLB_VERBOSE);
    > + }

    Just do this higher up and avoid calling is_realm_world() twice:

    unsigned int flags = SWIOTLB_VERBOSE;

    ...

    if (is_realm_world()) {
    swiotlb = true;
    flags |= SWIOTLB_FORCE;
    }

    ...

    swiotlb_init(swiotlb, flags);

    --
    Catalin

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