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iommu/vt-d: only unmap mapped entries
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Current unmap implementation unmaps the entire area covered by the IOVA
range, which is a power-of-2 aligned region. The corresponding map,
however, only maps those pages originally mapped by the user. This
discrepancy can lead to unmapping of already unmapped entries, which is
unneeded work.

With this patch, only mapped pages are unmapped. This is also a baseline
for a map/unmap implementation based on IOVAs and not iova structures,
which will allow caching.

Signed-off-by: Omer Peleg <omer@cs.technion.ac.il>
[mad@cs.technion.ac.il: rebased and reworded the commit message]
Signed-off-by: Adam Morrison <mad@cs.technion.ac.il>
Reviewed-by: Shaohua Li <shli@fb.com>
Reviewed-by: Ben Serebrin <serebrin@google.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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Omer Peleg authored and David Woodhouse committed Apr 20, 2016
1 parent f5c0c08 commit 769530e
Showing 1 changed file with 25 additions and 11 deletions.
36 changes: 25 additions & 11 deletions drivers/iommu/intel-iommu.c
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Original file line number Diff line number Diff line change
Expand Up @@ -459,6 +459,7 @@ static void flush_unmaps_timeout(unsigned long data);

struct deferred_flush_entry {
struct iova *iova;
unsigned long nrpages;
struct dmar_domain *domain;
struct page *freelist;
};
Expand Down Expand Up @@ -3542,17 +3543,17 @@ static void flush_unmaps(struct deferred_flush_data *flush_data)
struct deferred_flush_entry *entry =
&flush_table->entries[j];
struct iova *iova = entry->iova;
unsigned long nrpages = entry->nrpages;
struct dmar_domain *domain = entry->domain;
struct page *freelist = entry->freelist;

/* On real hardware multiple invalidations are expensive */
if (cap_caching_mode(iommu->cap))
iommu_flush_iotlb_psi(iommu, domain,
mm_to_dma_pfn(iova->pfn_lo),
mm_to_dma_pfn(iova_size(iova)),
!freelist, 0);
nrpages, !freelist, 0);
else {
mask = ilog2(mm_to_dma_pfn(iova_size(iova)));
mask = ilog2(nrpages);
iommu_flush_dev_iotlb(domain,
(uint64_t)iova->pfn_lo << PAGE_SHIFT, mask);
}
Expand All @@ -3576,7 +3577,8 @@ static void flush_unmaps_timeout(unsigned long cpuid)
spin_unlock_irqrestore(&flush_data->lock, flags);
}

static void add_unmap(struct dmar_domain *dom, struct iova *iova, struct page *freelist)
static void add_unmap(struct dmar_domain *dom, struct iova *iova,
unsigned long nrpages, struct page *freelist)
{
unsigned long flags;
int entry_id, iommu_id;
Expand Down Expand Up @@ -3610,6 +3612,7 @@ static void add_unmap(struct dmar_domain *dom, struct iova *iova, struct page *f
entry = &flush_data->tables[iommu_id].entries[entry_id];
entry->domain = dom;
entry->iova = iova;
entry->nrpages = nrpages;
entry->freelist = freelist;

if (!flush_data->timer_on) {
Expand All @@ -3622,10 +3625,11 @@ static void add_unmap(struct dmar_domain *dom, struct iova *iova, struct page *f
put_cpu();
}

static void intel_unmap(struct device *dev, dma_addr_t dev_addr)
static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size)
{
struct dmar_domain *domain;
unsigned long start_pfn, last_pfn;
unsigned long nrpages;
struct iova *iova;
struct intel_iommu *iommu;
struct page *freelist;
Expand All @@ -3643,8 +3647,9 @@ static void intel_unmap(struct device *dev, dma_addr_t dev_addr)
(unsigned long long)dev_addr))
return;

nrpages = aligned_nrpages(dev_addr, size);
start_pfn = mm_to_dma_pfn(iova->pfn_lo);
last_pfn = mm_to_dma_pfn(iova->pfn_hi + 1) - 1;
last_pfn = start_pfn + nrpages - 1;

pr_debug("Device %s unmapping: pfn %lx-%lx\n",
dev_name(dev), start_pfn, last_pfn);
Expand All @@ -3653,12 +3658,12 @@ static void intel_unmap(struct device *dev, dma_addr_t dev_addr)

if (intel_iommu_strict) {
iommu_flush_iotlb_psi(iommu, domain, start_pfn,
last_pfn - start_pfn + 1, !freelist, 0);
nrpages, !freelist, 0);
/* free iova */
__free_iova(&domain->iovad, iova);
dma_free_pagelist(freelist);
} else {
add_unmap(domain, iova, freelist);
add_unmap(domain, iova, nrpages, freelist);
/*
* queue up the release of the unmap to save the 1/6th of the
* cpu used up by the iotlb flush operation...
Expand All @@ -3670,7 +3675,7 @@ static void intel_unmap_page(struct device *dev, dma_addr_t dev_addr,
size_t size, enum dma_data_direction dir,
struct dma_attrs *attrs)
{
intel_unmap(dev, dev_addr);
intel_unmap(dev, dev_addr, size);
}

static void *intel_alloc_coherent(struct device *dev, size_t size,
Expand Down Expand Up @@ -3729,7 +3734,7 @@ static void intel_free_coherent(struct device *dev, size_t size, void *vaddr,
size = PAGE_ALIGN(size);
order = get_order(size);

intel_unmap(dev, dma_handle);
intel_unmap(dev, dma_handle, size);
if (!dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT))
__free_pages(page, order);
}
Expand All @@ -3738,7 +3743,16 @@ static void intel_unmap_sg(struct device *dev, struct scatterlist *sglist,
int nelems, enum dma_data_direction dir,
struct dma_attrs *attrs)
{
intel_unmap(dev, sglist[0].dma_address);
dma_addr_t startaddr = sg_dma_address(sglist) & PAGE_MASK;
unsigned long nrpages = 0;
struct scatterlist *sg;
int i;

for_each_sg(sglist, sg, nelems, i) {
nrpages += aligned_nrpages(sg_dma_address(sg), sg_dma_len(sg));
}

intel_unmap(dev, startaddr, nrpages << VTD_PAGE_SHIFT);
}

static int intel_nontranslate_map_sg(struct device *hddev,
Expand Down

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