[Xen-devel] [PATCH v7 2/6] iommu: introduce dom0-iommu option

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

To select the iommu configuration used by Dom0. This option supersedes
iommu=dom0-strict|dom0-passthrough.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Changes since v5:
 - Fix typo in docs.
 - Force iommu_hwdom_passthrough to false for PVH Dom0. Note this in
   the documentation.

Changes since v4:
 - Move the iommu_dom0_* variable renaming to a previous patch.
 - Use dom0-iommu=passthrough|strict booleans, like the iommu option
   used.

Changes since v2:
 - Change the style and text used in the xen command line document.
 - Don't allow none, strict or relaxed to use the no- prefix.

Changes since v1:
 - New in this version.
---
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 docs/misc/xen-command-line.markdown | 21 +++++++++++++++++++
 xen/drivers/passthrough/iommu.c     | 31 +++++++++++++++++++++++++----
 2 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index 559c0662fa..cd57960ede 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -681,6 +681,21 @@ Flag that makes a dom0 boot in PVHv2 mode.
 Flag that makes a dom0 use shadow paging. Only works when "pvh" is
 enabled.
 
+### dom0-iommu
+> `= List of [ passthrough | strict ]`
+
+This list of booleans controls the iommu usage by Dom0:
+
+* `passthrough`: disables DMA remapping for Dom0. Default is `false`. Note that
+  this option is hard coded to `false` for a PVH Dom0 and any attempt to
+  overwrite it from the command line is ignored.
+
+* `strict`: sets up DMA remapping only for the RAM Dom0 actually got assigned.
+  Default is `false` which means Dom0 will get mappings for all the host
+  RAM except regions in use by Xen. Note that this option is hard coded to
+  `true` for a PVH Dom0 and any attempt to overwrite it from the command line
+  is ignored.
+
 ### dom0\_ioports\_disable (x86)
 > `= List of <hex>-<hex>`
 
@@ -1152,12 +1167,18 @@ detection of systems known to misbehave upon accesses 
to that port.
 
 > `dom0-passthrough`
 
+> **WARNING: This command line option is deprecated, and superseded by
+> _dom0-iommu=passthrough_ - using both options in combination is undefined.**
+
 > Default: `false`
 
 >> Control whether to disable DMA remapping for Dom0.
 
 > `dom0-strict`
 
+> **WARNING: This command line option is deprecated, and superseded by
+> _dom0-iommu=strict_ - using both options in combination is undefined.**
+
 > Default: `false`
 
 >> Control whether to set up DMA remapping only for the memory Dom0 actually
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 729ee5c373..8f9975cf4e 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -136,6 +136,32 @@ static int __init parse_iommu_param(const char *s)
     return rc;
 }
 
+static int __init parse_dom0_iommu_param(const char *s)
+{
+    const char *ss;
+    int rc = 0;
+
+    do {
+        int val;
+
+        ss = strchr(s, ',');
+        if ( !ss )
+            ss = strchr(s, '\0');
+
+        if ( (val = parse_boolean("passthrough", s, ss)) >= 0 )
+            iommu_hwdom_passthrough = val;
+        else if ( (val = parse_boolean("strict", s, ss)) >= 0 )
+            iommu_hwdom_strict = val;
+        else
+            rc = -EINVAL;
+
+        s = ss + 1;
+    } while ( *ss );
+
+    return rc;
+}
+custom_param("dom0-iommu", parse_dom0_iommu_param);
+
 int iommu_domain_init(struct domain *d)
 {
     struct domain_iommu *hd = dom_iommu(d);
@@ -159,10 +185,7 @@ static void __hwdom_init check_hwdom_reqs(struct domain *d)
 
     arch_iommu_check_autotranslated_hwdom(d);
 
-    if ( iommu_hwdom_passthrough )
-        panic("Dom0 uses paging translated mode, dom0-passthrough must not be "
-              "enabled\n");
-
+    iommu_hwdom_passthrough = false;
     iommu_hwdom_strict = true;
 }
 
-- 
2.18.0


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