From 606d8a8ad41c307aa763579e50f81c565c210f48 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Fri, 11 Nov 2011 17:26:44 -0700 Subject: [PATCH] intel-iommu: Default to non-coherent for domains unattached to iommus commit 2e12bc29fc5a12242d68e11875db3dd58efad9ff upstream. domain_update_iommu_coherency() currently defaults to setting domains as coherent when the domain is not attached to any iommus. This allows for a window in domain_context_mapping_one() where such a domain can update context entries non-coherently, and only after update the domain capability to clear iommu_coherency. This can be seen using KVM device assignment on VT-d systems that do not support coherency in the ecap register. When a device is added to a guest, a domain is created (iommu_coherency = 0), the device is attached, and ranges are mapped. If we then hot unplug the device, the coherency is updated and set to the default (1) since no iommus are attached to the domain. A subsequent attach of a device makes use of the same dmar domain (now marked coherent) updates context entries with coherency enabled, and only disables coherency as the last step in the process. To fix this, switch domain_update_iommu_coherency() to use the safer, non-coherent default for domains not attached to iommus. Signed-off-by: Alex Williamson Tested-by: Donald Dutile Acked-by: Donald Dutile Acked-by: Chris Wright Signed-off-by: Joerg Roedel [bwh: Backported to 3.2: dmar_domain::iommu_bmp is a single unsigned long not an array, so add &] Signed-off-by: Ben Hutchings --- drivers/iommu/intel-iommu.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c index ccf347f12c8a..b9062c0d3941 100644 --- a/drivers/iommu/intel-iommu.c +++ b/drivers/iommu/intel-iommu.c @@ -563,7 +563,9 @@ static void domain_update_iommu_coherency(struct dmar_domain *domain) { int i; - domain->iommu_coherency = 1; + i = find_first_bit(&domain->iommu_bmp, g_num_of_iommus); + + domain->iommu_coherency = i < g_num_of_iommus ? 1 : 0; for_each_set_bit(i, &domain->iommu_bmp, g_num_of_iommus) { if (!ecap_coherent(g_iommus[i]->ecap)) { -- 2.39.2