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authorDavid Woodhouse <dwmw2@infradead.org>2014-03-11 17:10:29 -0700
committerDavid Woodhouse <David.Woodhouse@intel.com>2014-03-19 17:25:48 +0000
commitd05019608746240d86a406fbf8d8c1fc71a87101 (patch)
tree8a5732ae72564c14dfa1013f7904be53b911734c /drivers/iommu
parent214e39aa36c9c02355d388f20d83b93fc2fa7298 (diff)
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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: David Woodhouse <David.Woodhouse@intel.com>
Diffstat (limited to 'drivers/iommu')
-rw-r--r--drivers/iommu/intel-iommu.c21
1 files changed, 17 insertions, 4 deletions
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index c3d4bc91a189..1599cb1e041c 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -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)