[PATCH v6 07/11] xen/arm: implement FIXMAP_ADDR for MPU systems

[Wei Chen <wei.chen@xxxxxxx>]

FIXMAP is a special virtual address section for Xen to map some
physical ram or device memory temporarily in initialization for
MMU systems. FIXMAP_ADDR will return a virtual address by index
for special purpose phys-to-virt mapping usage. For example,
FIXMAP_ADDR(FIXMAP_CONSOLE) for early console mapping and
FIXMAP_ADDR(FIXMAP_MISC) for copy_from_paddr.

But in MPU systems, we can't map physical address to any virtual
address. So we want the code that is using FIXMAP_ADDR to return
the input physical address in MPU systems. So in MPU version,
FIXMAP_ADDR will trim physical address to PAGE alignment. This
will return an offset which is similar to MMU version FIXMAP_ADDR.
But it's a physical offset got from input physical address, plus
to an offset inside page (which is also got from physical address
mask with PAGE_MASK). The caller can return the input physical
address directly.

As pmap depends on FIXAMP, so we disable pmap for Arm with MPU
enabled systems.

Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
---
 xen/arch/arm/Kconfig                  |  2 +-
 xen/arch/arm/include/asm/config_mpu.h |  2 ++
 xen/arch/arm/include/asm/fixmap.h     | 25 +++++++++++++++++++++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index ac276307d6..1458ffa777 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -16,7 +16,7 @@ config ARM
        select HAS_DEVICE_TREE
        select HAS_PASSTHROUGH
        select HAS_PDX
-       select HAS_PMAP
+       select HAS_PMAP if !HAS_MPU
        select IOMMU_FORCE_PT_SHARE
 
 config ARCH_DEFCONFIG
diff --git a/xen/arch/arm/include/asm/config_mpu.h 
b/xen/arch/arm/include/asm/config_mpu.h
index 530abb8302..eee60dcffc 100644
--- a/xen/arch/arm/include/asm/config_mpu.h
+++ b/xen/arch/arm/include/asm/config_mpu.h
@@ -24,4 +24,6 @@
 
 #define HYPERVISOR_VIRT_START  XEN_VIRT_START
 
+#define FIXMAP_ADDR(n)         (_AT(paddr_t, n) & (PAGE_MASK))
+
 #endif /* __ARM_CONFIG_MPU_H__ */
diff --git a/xen/arch/arm/include/asm/fixmap.h 
b/xen/arch/arm/include/asm/fixmap.h
index d0c9a52c8c..1e338759e9 100644
--- a/xen/arch/arm/include/asm/fixmap.h
+++ b/xen/arch/arm/include/asm/fixmap.h
@@ -7,6 +7,8 @@
 #include <xen/acpi.h>
 #include <xen/pmap.h>
 
+#ifndef CONFIG_HAS_MPU
+
 /* Fixmap slots */
 #define FIXMAP_CONSOLE  0  /* The primary UART */
 #define FIXMAP_MISC     1  /* Ephemeral mappings of hardware */
@@ -45,4 +47,27 @@ static inline unsigned int virt_to_fix(vaddr_t vaddr)
 
 #endif /* __ASSEMBLY__ */
 
+#else
+
+/*
+ * FIXMAP_ADDR will trim physical address to PAGE alignment.
+ * This will return an offset which is similar to MMU version
+ * FIXMAP_ADDR.
+ * For example:
+ * EARLY_UART_VIRTUAL_ADDRESS is defined by:
+ *     (FIXMAP_ADDR(FIXMAP_CONSOLE) + \
+ *     (CONFIG_EARLY_UART_BASE_ADDRESS & ~PAGE_MASK))
+ * With MPU version FIXMAP_CONSOLE and FIXMAP_ADDR definitions,
+ * EARLY_UART_VIRTUAL_ADDRESS can be restore to
+ * CONFIG_EARLY_UART_BASE_ADDRESS.
+ * In this case, we don't need to use #ifdef MPU in the code
+ * where are using FIXMAP_ADDR to make them to use physical
+ * address explicitily.
+ */
+#ifdef CONFIG_EARLY_UART_BASE_ADDRESS
+#define FIXMAP_CONSOLE         CONFIG_EARLY_UART_BASE_ADDRESS
+#endif
+
+#endif /* CONFIG_HAS_MPU */
+
 #endif /* __ASM_FIXMAP_H */
-- 
2.25.1