[Xen-devel] [PATCH 1/2] amd-iommu: obtain page_alloc_lock before traversing a domain's page list

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>From all I can tell, this doesn't violate lock ordering as other places
call heap allocation functions from inside hd->mapping_lock.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- 2009-01-27.orig/xen/drivers/passthrough/amd/iommu_map.c     2009-01-29 
11:33:26.000000000 +0100
+++ 2009-01-27/xen/drivers/passthrough/amd/iommu_map.c  2009-01-30 
08:43:35.000000000 +0100
@@ -567,6 +567,8 @@ int amd_iommu_sync_p2m(struct domain *d)
     if ( hd->p2m_synchronized )
         goto out;
 
+    spin_lock(&d->page_alloc_lock);
+
     page_list_for_each ( page, &d->page_list )
     {
         mfn = page_to_mfn(page);
@@ -579,6 +581,7 @@ int amd_iommu_sync_p2m(struct domain *d)
 
         if ( iommu_l2e == 0 )
         {
+            spin_unlock(&d->page_alloc_lock);
             amd_iov_error("Invalid IO pagetable entry gfn = %lx\n", gfn);
             spin_unlock_irqrestore(&hd->mapping_lock, flags);
             return -EFAULT;
@@ -587,6 +590,8 @@ int amd_iommu_sync_p2m(struct domain *d)
         set_iommu_l1e_present(iommu_l2e, gfn, (u64)mfn << PAGE_SHIFT, iw, ir);
     }
 
+    spin_unlock(&d->page_alloc_lock);
+
     hd->p2m_synchronized = 1;
 
 out:




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