[PATCH v3 07/12] xen: introduce domain-layout.h with common domain_use_host_layout()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

domain_use_host_layout() is not architecture-specific and may be needed
on x86 [1]. Replace the ARM-specific macro in asm/domain.h with a common
static inline in a new dedicated header, xen/domain-layout.h.

xen/domain.h would be the natural home, but placing it there would
require including xen/paging.h (for paging_mode_translate()) and
xen/sched.h (for is_hardware_domain()), which would introduce circular
dependencies. A separate header that callers opt into avoids this.

Adjust the implementation to take paging_mode_translate() into account
so it works correctly for all architectures, including x86. Some extra
details about implementation [2] and [3].

[1] 
https://lore.kernel.org/xen-devel/alpine.DEB.2.22.394.2602161038120.359097@ubuntu-linux-20-04-desktop/
[2] 
https://lore.kernel.org/xen-devel/alpine.DEB.2.22.394.2602271742400.3148344@ubuntu-linux-20-04-desktop/
[3] 
https://lore.kernel.org/xen-devel/alpine.DEB.2.22.394.2602271750190.3148344@ubuntu-linux-20-04-desktop/

Suggested-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in v3:
 - Make argument of domain_use_host_layout() const.
 - Create a separate header to avoid circular heder dependecy and making
   domain_use_host_layour() as static inline.
 - Rework domain_use_host_layout() to be protected by paging_mode_translate().
 - Update the commit message.
---
Changes in v2:
 - Drop ifdef around defintion of domain_use_host_layout() as it
   was suggested generic version. It could be returned back when
   the real use case for it will appear.
 - Add Suggested-by: and update the commit message.
 - Make domain_use_host_layout() function instead of macros to
   avoid ciclular header dependecies. Look at more details in
   the commit message.
---
 xen/arch/arm/domain_build.c           |  1 +
 xen/arch/arm/include/asm/domain.h     | 14 --------------
 xen/arch/arm/vgic-v3.c                |  1 +
 xen/common/device-tree/domain-build.c |  1 +
 xen/include/xen/domain-layout.h       | 28 +++++++++++++++++++++++++++
 5 files changed, 31 insertions(+), 14 deletions(-)
 create mode 100644 xen/include/xen/domain-layout.h

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 6c17a84b2633..60a7cbf915a5 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2,6 +2,7 @@
 #include <xen/init.h>
 #include <xen/bootinfo.h>
 #include <xen/compile.h>
+#include <xen/domain-layout.h>
 #include <xen/dom0less-build.h>
 #include <xen/fdt-domain-build.h>
 #include <xen/fdt-kernel.h>
diff --git a/xen/arch/arm/include/asm/domain.h 
b/xen/arch/arm/include/asm/domain.h
index ffe5d0d9f0a6..f95ad1285e6e 100644
--- a/xen/arch/arm/include/asm/domain.h
+++ b/xen/arch/arm/include/asm/domain.h
@@ -30,20 +30,6 @@ enum domain_type {
 #define is_64bit_domain(d) (0)
 #endif
 
-/*
- * Is the domain using the host memory layout?
- *
- * Direct-mapped domain will always have the RAM mapped with GFN == MFN.
- * To avoid any trouble finding space, it is easier to force using the
- * host memory layout.
- *
- * The hardware domain will use the host layout regardless of
- * direct-mapped because some OS may rely on a specific address ranges
- * for the devices.
- */
-#define domain_use_host_layout(d) (is_domain_direct_mapped(d) || \
-                                   is_hardware_domain(d))
-
 struct vtimer {
     struct vcpu *v;
     int irq;
diff --git a/xen/arch/arm/vgic-v3.c b/xen/arch/arm/vgic-v3.c
index 77aab5c3c293..77517c303061 100644
--- a/xen/arch/arm/vgic-v3.c
+++ b/xen/arch/arm/vgic-v3.c
@@ -10,6 +10,7 @@
  */
 
 #include <xen/bitops.h>
+#include <xen/domain-layout.h>
 #include <xen/init.h>
 #include <xen/irq.h>
 #include <xen/lib.h>
diff --git a/xen/common/device-tree/domain-build.c 
b/xen/common/device-tree/domain-build.c
index 540627b74e96..e706a6173ba6 100644
--- a/xen/common/device-tree/domain-build.c
+++ b/xen/common/device-tree/domain-build.c
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #include <xen/bootinfo.h>
+#include <xen/domain-layout.h>
 #include <xen/fdt-domain-build.h>
 #include <xen/init.h>
 #include <xen/lib.h>
diff --git a/xen/include/xen/domain-layout.h b/xen/include/xen/domain-layout.h
new file mode 100644
index 000000000000..15cbb1813c8a
--- /dev/null
+++ b/xen/include/xen/domain-layout.h
@@ -0,0 +1,28 @@
+#ifndef __XEN_DOMAIN_LAYOUT_H__
+#define __XEN_DOMAIN_LAYOUT_H__
+
+#include <xen/domain.h>
+#include <xen/paging.h>
+#include <xen/sched.h>
+
+/*
+ * Is a domain using the host memory layout?
+ *
+ * domain_use_host_layout() is always False for PV guests.
+ *
+ * Direct-mapped domains (autotranslated domains with memory allocated
+ * contiguously and mapped 1:1 so that GFN == MFN) are always using the
+ * host memory layout to avoid address clashes.
+ *
+ * The hardware domain will use the host layout (regardless of
+ * direct-mapped) because some OS may rely on specific address ranges
+ * for the devices. PV Dom0, like any other PV guests, has
+ * domain_use_host_layout() returning False.
+ */
+static inline bool domain_use_host_layout(const struct domain *d)
+{
+    return paging_mode_translate(d) &&
+           (is_domain_direct_mapped(d) || is_hardware_domain(d));
+}
+
+#endif /* __XEN_DOMAIN_LAYOUT_H__ */
-- 
2.53.0