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iommu/dma: simplify dma_iova_destroy() and drop the free_iova helper

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dma_iova_destroy() frees the IOVA space through __iommu_dma_iova_unlink()
using a "free_iova" boolean, which duplicates the IOVA free logic in
dma_iova_free(). And it frees using the unmapped @mapped_len, which for a
partially linked reservation is smaller than the reserved size. This
results in a benign waste as pointed out by Robin, not a leak. So this is
a cleanup, not a fix.

Drop the duplicated free path. Fold __iommu_dma_iova_unlink into
dma_iova_unlink and remove the free_iova parameter so it only unmaps.
dma_iova_destroy then unlinks the mapped range if mapped_len is set and
unconditionally calls dma_iova_free, which frees the whole reservation
via dma_iova_size. The freed size now always matches the reserved size,
and destroy reads as unlink then free.

Note that dma_iova_destroy() no longer routes the free through the flush
queue; teardown now unmaps synchronously and frees directly, matching
dma_iova_free().

No functional change intended for callers.

Suggested-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Honglei Huang <honghuan@amd.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260703033729.455358-1-honghuan@amd.com
This commit is contained in:
Honglei Huang
2026-07-03 11:37:29 +08:00
committed by Marek Szyprowski
parent dbcc3cd580
commit 1acce29926
1 changed files with 28 additions and 41 deletions
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69
drivers/iommu/dma-iommu.c
View File

@@ -2068,38 +2068,6 @@ static void iommu_dma_iova_unlink_range_slow(struct device *dev,
arch_sync_dma_flush();
}
static void __iommu_dma_iova_unlink(struct device *dev,
struct dma_iova_state *state, size_t offset, size_t size,
enum dma_data_direction dir, unsigned long attrs,
bool free_iova)
{
struct iommu_domain *domain = iommu_get_dma_domain(dev);
struct iommu_dma_cookie *cookie = domain->iova_cookie;
struct iova_domain *iovad = &cookie->iovad;
dma_addr_t addr = state->addr + offset;
size_t iova_start_pad = iova_offset(iovad, addr);
struct iommu_iotlb_gather iotlb_gather;
size_t unmapped;
if ((state->__size & DMA_IOVA_USE_SWIOTLB) ||
(!dev_is_dma_coherent(dev) &&
!(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO))))
iommu_dma_iova_unlink_range_slow(dev, addr, size, dir, attrs);
iommu_iotlb_gather_init(&iotlb_gather);
iotlb_gather.queued = free_iova && READ_ONCE(cookie->fq_domain);
size = iova_align(iovad, size + iova_start_pad);
addr -= iova_start_pad;
unmapped = iommu_unmap_fast(domain, addr, size, &iotlb_gather);
WARN_ON(unmapped != size);
if (!iotlb_gather.queued)
iommu_iotlb_sync(domain, &iotlb_gather);
if (free_iova)
iommu_dma_free_iova(domain, addr, size, &iotlb_gather);
}
/**
* dma_iova_unlink - Unlink a range of IOVA space
* @dev: DMA device
@@ -2115,7 +2083,27 @@ void dma_iova_unlink(struct device *dev, struct dma_iova_state *state,
size_t offset, size_t size, enum dma_data_direction dir,
unsigned long attrs)
{
__iommu_dma_iova_unlink(dev, state, offset, size, dir, attrs, false);
struct iommu_domain *domain = iommu_get_dma_domain(dev);
struct iommu_dma_cookie *cookie = domain->iova_cookie;
struct iova_domain *iovad = &cookie->iovad;
dma_addr_t addr = state->addr + offset;
size_t iova_start_pad = iova_offset(iovad, addr);
struct iommu_iotlb_gather iotlb_gather;
size_t unmapped;
if ((state->__size & DMA_IOVA_USE_SWIOTLB) ||
(!dev_is_dma_coherent(dev) &&
!(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO))))
iommu_dma_iova_unlink_range_slow(dev, addr, size, dir, attrs);
iommu_iotlb_gather_init(&iotlb_gather);
size = iova_align(iovad, size + iova_start_pad);
addr -= iova_start_pad;
unmapped = iommu_unmap_fast(domain, addr, size, &iotlb_gather);
WARN_ON(unmapped != size);
iommu_iotlb_sync(domain, &iotlb_gather);
}
EXPORT_SYMBOL_GPL(dma_iova_unlink);
@@ -2136,14 +2124,13 @@ void dma_iova_destroy(struct device *dev, struct dma_iova_state *state,
unsigned long attrs)
{
if (mapped_len)
__iommu_dma_iova_unlink(dev, state, 0, mapped_len, dir, attrs,
true);
else
/*
* We can be here if first call to dma_iova_link() failed and
* there is nothing to unlink, so let's be more clear.
*/
dma_iova_free(dev, state);
dma_iova_unlink(dev, state, 0, mapped_len, dir, attrs);
/*
* We can be here if the first call to dma_iova_link() failed and
* there is nothing to unlink, so let's be more clear.
*/
dma_iova_free(dev, state);
}
EXPORT_SYMBOL_GPL(dma_iova_destroy);