linux-kernel - [PATCH 0/8] Large DMA alloc/skip 32-bit alloc if size

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Message-ID: <CAEHaoC22NDpHUWovJChCx_XqchkEvUPYrFFe_L1PH9Mw2e386A@mail.gmail.com>
Date: Sun, 3 Aug 2025 14:01:53 +0300
From: Constantine Gavrilov <cgavrilov@...inidat.com>
To: linux-kernel@...r.kernel.org, Marek Szyprowski <m.szyprowski@...sung.com>, 
	Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev
Subject: [PATCH 0/8] Large DMA alloc/skip 32-bit alloc if size > 32-bit

This is the first patch from the set of patches that enable large IOMMU
DMA registrations. Entire work is available at the master branch of the
master branch of git@...hub.com:cgavrilov/linux.git repo.

Do not consider 32-bit range allocation and skip iterating the rbtree,
if the allocation size exceeds 32-bit.

commit 1c21c64befe18d626855a828c721eb786dbb69b8
Author: Constantine Gavrilov <cgavrilov@...inidat.com>
Date:   Sun Jun 22 13:05:26 2025 +0300

    iommu_dma_alloc_iova(): do not try to allocate 32-bit address if
the size is above 32-bit.

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index ea2ef53bd4fe..8280e8864ef3 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -772,7 +772,7 @@ static dma_addr_t iommu_dma_alloc_iova(struct
iommu_domain *domain,
      * some inherent bug in handling >32-bit addresses, or not all the
      * expected address bits are wired up between the device and the IOMMU.
      */
-    if (dma_limit > DMA_BIT_MASK(32) && dev->iommu->pci_32bit_workaround) {
+    if (dma_limit > DMA_BIT_MASK(32) && (size - 1) <=
DMA_BIT_MASK(32) && dev->iommu->pci_32bit_workaround) {
         iova = alloc_iova_fast(iovad, iova_len,
                        DMA_BIT_MASK(32) >> shift, false);
         if (iova)

-- 
----------------------------------------
Constantine Gavrilov
System Architect and Platform Engineer
Infinidat
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