[Xen-devel] [PATCH v4 2/3] xen/dom0: Deprecate iommu_hwdom_inclusive and leave it disabled by default

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

This option is unique to x86 PV dom0's, but it is not sensible to have a
catch-all which blindly maps all non-RAM regions into the IOMMU.

The map-reserved option remains, and covers all the buggy firmware issues that
I am aware of.  The two common cases are legacy USB keyboard emulation, and
the BMC mailbox used by vendor firmware in NICs/HBAs to report information
back to the iLO/iDRAC/etc for remote remote management purposes.

A specific advantage of this change is that x86 dom0's IOMMU setup is now
consistent between PV and PVH.

This change is not expected to have any impact, due to map-reserved remaining.
In the unlikely case that it does cause an issue, we should introduce other
map-$SPECIFIC options rather than re-introducing this catch-all.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>

v2:
 * New
v4:
 * Switch to only disabled-by-default and deprecated, rather than revmoving
   the option fully.
---
 docs/misc/xen-command-line.pandoc   | 10 ++++++----
 xen/drivers/passthrough/iommu.c     |  2 +-
 xen/drivers/passthrough/x86/iommu.c |  3 ---
 3 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/docs/misc/xen-command-line.pandoc 
b/docs/misc/xen-command-line.pandoc
index 8b1703d..139c4e1 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -707,14 +707,16 @@ Controls for the dom0 IOMMU setup.
     Where possible, finer grain corrections should be made with the `rmrr=`,
     `ivrs_hpet=` or `ivrs_ioapic=` command line options.
 
-    This option is enabled by default on x86 systems, and invalid on ARM
-    systems.
+    This option is disabled by default, and deprecated and intended for
+    removal in future versions of Xen.  If specifying `map-inclusive` is the
+    only way to make your system boot, please report a bug.
 
 *   The `map-reserved` functionality is very similar to `map-inclusive`.
 
     The differences from `map-inclusive` are that `map-reserved` is applicable
-    to both x86 PV and PVH dom0's, and represents a subset of the correction
-    by only mapping reserved memory regions rather than all non-RAM regions.
+    to both x86 PV and PVH dom0's, is enabled by default, and represents a
+    subset of the correction by only mapping reserved memory regions rather
+    than all non-RAM regions.
 
 ### dom0_ioports_disable (x86)
 > `= List of <hex>-<hex>`
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 9ac9e05..b9ffe18 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -38,7 +38,7 @@ bool_t __read_mostly iommu_intremap = 1;
 
 bool __hwdom_initdata iommu_hwdom_strict;
 bool __read_mostly iommu_hwdom_passthrough;
-int8_t __hwdom_initdata iommu_hwdom_inclusive = -1;
+int8_t __hwdom_initdata iommu_hwdom_inclusive;
 int8_t __hwdom_initdata iommu_hwdom_reserved = -1;
 
 /*
diff --git a/xen/drivers/passthrough/x86/iommu.c 
b/xen/drivers/passthrough/x86/iommu.c
index e40d7a7..2c051a0 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -214,9 +214,6 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
 
     BUG_ON(!is_hardware_domain(d));
 
-    /* Inclusive mappings are enabled by default for PV. */
-    if ( iommu_hwdom_inclusive == -1 )
-        iommu_hwdom_inclusive = is_pv_domain(d);
     /* Reserved IOMMU mappings are enabled by default. */
     if ( iommu_hwdom_reserved == -1 )
         iommu_hwdom_reserved = 1;
-- 
2.1.4


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