x86/iommu: account for necessary allocations when calculating Dom0's initial allocati...

As of c/s 21812:e382656e4dcc, IOMMU related allocations for Dom0
happen only after it got all of its memory allocated, and hence the
reserve (mainly for setting up its swiotlb) may get exhausted without
accounting for the necessary allocations up front.

While not precise, the estimate has been found to be within a couple
of pages for the systems it got tested on.

For the calculation to be reasonably correct, this depends on the
patch titled "x86/iommu: don't map RAM holes above 4G" sent out
yesterday.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

diff --git a/xen/arch/x86/domain_build.c b/xen/arch/x86/domain_build.c
index aaf7055c8e2d65d0be46120e6bdfd0f1a18ab690..57b9bef42104efd2d2de061ae250a22cd6e3f708 100644 (file)
--- a/xen/arch/x86/domain_build.c
+++ b/xen/arch/x86/domain_build.c
@@ -191,6 +191,15 @@ static unsigned long __init compute_dom0_nr_pages(
     if ( is_pv_32on64_domain(d) )
         avail -= opt_dom0_max_vcpus - 1;
 
+    /* Reserve memory for iommu_dom0_init() (rough estimate). */
+    if ( iommu_enabled )
+    {
+        unsigned int s;
+
+        for ( s = 9; s < BITS_PER_LONG; s += 9 )
+            avail -= max_pdx >> s;
+    }
+
     /*
      * If domain 0 allocation isn't specified, reserve 1/16th of available
      * memory for things like DMA buffers. This reservation is clamped to