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Commit d0501960 authored by David Woodhouse's avatar David Woodhouse Committed by David Woodhouse
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iommu/vt-d: Be less pessimistic about domain coherency where possible 



In commit 2e12bc29 ("intel-iommu: Default to non-coherent for domains
unattached to iommus") we decided to err on the side of caution and
always assume that it's possible that a device will be attached which is
behind a non-coherent IOMMU.

In some cases, however, that just *cannot* happen. If there *are* no
IOMMUs in the system which are non-coherent, then we don't need to do
it. And flushing the dcache is a *significant* performance hit.

Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent 214e39aa

drivers/iommu/intel-iommu.c

+17 −4
Original line number Diff line number Diff line
@@ -592,18 +592,31 @@ static struct intel_iommu *domain_get_iommu(struct dmar_domain *domain) 


static void domain_update_iommu_coherency(struct dmar_domain *domain)

{

	int i;



	i = find_first_bit(domain->iommu_bmp, g_num_of_iommus);

	struct dmar_drhd_unit *drhd;

	struct intel_iommu *iommu;

	int i, found = 0;



	domain->iommu_coherency = i < g_num_of_iommus ? 1 : 0;

	domain->iommu_coherency = 1;



	for_each_set_bit(i, domain->iommu_bmp, g_num_of_iommus) {

		found = 1;

		if (!ecap_coherent(g_iommus[i]->ecap)) {

			domain->iommu_coherency = 0;

			break;

		}

	}

	if (found)

		return;



	/* No hardware attached; use lowest common denominator */

	rcu_read_lock();

	for_each_active_iommu(iommu, drhd) {

		if (!ecap_coherent(iommu->ecap)) {

			domain->iommu_coherency = 0;

			break;

		}

	}

	rcu_read_unlock();

}



static void domain_update_iommu_snooping(struct dmar_domain *domain)