VT-d: re-phrase logic in vtd_set_hwdom_mapping() for clarity

It is hard to reconcile the comment at the top of the loop in
vtd_set_hwdom_mapping() with the if statement following it. This patch
re-phrases the logic, preserving the semantics, but making it easier
to read.

The patch also modifies the Xen command line documentation to make it
clear that iommu_inclusive_mapping only applies to pages up to the 4GB
boundary.

NOTE: This patch also corrects the indentation of the printk() towards
      the end of vtd_set_hwdom_mapping().

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Roger Pau Monne <roger.pau@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index 075e5ea1599e26092e06a17721dd765820b8a4de..c0b7724ae962aaff45267a8dd1f37f1cb84813b1 100644 (file)
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1212,8 +1212,8 @@ wait descriptor timed out', try increasing this value.
 
 Use this to work around firmware issues providing incorrect RMRR entries.
 Rather than only mapping RAM pages for IOMMU accesses for Dom0, with this
-option all pages not marked as unusable in the E820 table will get a mapping
-established.
+option all pages up to 4GB, not marked as unusable in the E820 table, will
+get a mapping established.
 
 ### irq\_ratelimit (x86)
 > `= <integer>`

diff --git a/xen/drivers/passthrough/vtd/x86/vtd.c b/xen/drivers/passthrough/vtd/x86/vtd.c
index 88a60b330752591dcd2a7084086d7a76995d8478..2938f69fbb3061a853a273806a6915bd972aafe6 100644 (file)
--- a/xen/drivers/passthrough/vtd/x86/vtd.c
+++ b/xen/drivers/passthrough/vtd/x86/vtd.c
@@ -110,30 +110,34 @@ void hvm_dpci_isairq_eoi(struct domain *d, unsigned int isairq)
 
 void __hwdom_init vtd_set_hwdom_mapping(struct domain *d)
 {
-    unsigned long i, j, tmp, top;
+    unsigned long i, j, tmp, top, max_pfn;
 
     BUG_ON(!is_hardware_domain(d));
 
-    top = max(max_pdx, pfn_to_pdx(0xffffffffUL >> PAGE_SHIFT) + 1);
+    max_pfn = (GB(4) >> PAGE_SHIFT) - 1;
+    top = max(max_pdx, pfn_to_pdx(max_pfn) + 1);
 
     for ( i = 0; i < top; i++ )
     {
+        unsigned long pfn = pdx_to_pfn(i);
+        bool map;
         int rc = 0;
 
         /*
-         * Set up 1:1 mapping for dom0. Default to use only conventional RAM
-         * areas and let RMRRs include needed reserved regions. When set, the
-         * inclusive mapping maps in everything below 4GB except unusable
-         * ranges.
+         * Set up 1:1 mapping for dom0. Default to include only
+         * conventional RAM areas and let RMRRs include needed reserved
+         * regions. When set, the inclusive mapping additionally maps in
+         * every pfn up to 4GB except those that fall in unusable ranges.
          */
-        unsigned long pfn = pdx_to_pfn(i);
+        if ( pfn > max_pfn && !mfn_valid(_mfn(pfn)) )
+            continue;
+
+        if ( iommu_inclusive_mapping && pfn <= max_pfn )
+            map = !page_is_ram_type(pfn, RAM_TYPE_UNUSABLE);
+        else
+            map = page_is_ram_type(pfn, RAM_TYPE_CONVENTIONAL);
 
-        if ( pfn > (0xffffffffUL >> PAGE_SHIFT) ?
-             (!mfn_valid(_mfn(pfn)) ||
-              !page_is_ram_type(pfn, RAM_TYPE_CONVENTIONAL)) :
-             iommu_inclusive_mapping ?
-             page_is_ram_type(pfn, RAM_TYPE_UNUSABLE) :
-             !page_is_ram_type(pfn, RAM_TYPE_CONVENTIONAL) )
+        if ( !map )
             continue;
 
         /* Exclude Xen bits */
@@ -151,8 +155,8 @@ void __hwdom_init vtd_set_hwdom_mapping(struct domain *d)
         }
 
         if ( rc )
-           printk(XENLOG_WARNING VTDPREFIX " d%d: IOMMU mapping failed: %d\n",
-                  d->domain_id, rc);
+            printk(XENLOG_WARNING VTDPREFIX " d%d: IOMMU mapping failed: %d\n",
+                   d->domain_id, rc);
 
         if (!(i & (0xfffff >> (PAGE_SHIFT - PAGE_SHIFT_4K))))
             process_pending_softirqs();