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intel-iommu: Performance improvement for dma_pte_clear_range() 

It's a bit silly to repeatedly call domain_flush_cache() for each PTE
individually, as we clear it. Instead, batch them up and flush a whole
range at a time. We might as well refrain from recalculating the PTE
address from scratch each time round the loop too.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
David Woodhouse 2009-06-28 18:52:20 +01:00
parent c5395d5c4a
commit 310a5ab93c
1 changed files with 15 additions and 16 deletions
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29
drivers/pci/intel-iommu.c
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@ -761,34 +761,33 @@ static struct dma_pte *dma_pfn_level_pte(struct dmar_domain *domain,
return NULL;
}
/* clear one page's page table */
static void dma_pte_clear_one(struct dmar_domain *domain, unsigned long pfn)
{
struct dma_pte *pte = NULL;
/* get last level pte */
pte = dma_pfn_level_pte(domain, pfn, 1);
if (pte) {
dma_clear_pte(pte);
domain_flush_cache(domain, pte, sizeof(*pte));
}
}
/* clear last level pte, a tlb flush should be followed */
static void dma_pte_clear_range(struct dmar_domain *domain,
unsigned long start_pfn,
unsigned long last_pfn)
{
int addr_width = agaw_to_width(domain->agaw) - VTD_PAGE_SHIFT;
struct dma_pte *first_pte, *pte;
BUG_ON(addr_width < BITS_PER_LONG && start_pfn >> addr_width);
BUG_ON(addr_width < BITS_PER_LONG && last_pfn >> addr_width);
/* we don't need lock here; nobody else touches the iova range */
while (start_pfn <= last_pfn) {
dma_pte_clear_one(domain, start_pfn);
first_pte = pte = dma_pfn_level_pte(domain, start_pfn, 1);
if (!pte) {
start_pfn = align_to_level(start_pfn + 1, 2);
continue;
}
while (start_pfn <= last_pfn &&
(unsigned long)pte >> VTD_PAGE_SHIFT ==
(unsigned long)first_pte >> VTD_PAGE_SHIFT) {
dma_clear_pte(pte);
start_pfn++;
pte++;
}
domain_flush_cache(domain, first_pte,
(void *)pte - (void *)first_pte);
}
}