Hi Wei,
On 04/11/2022 10:07, Wei Chen wrote:
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.
To me, we are bending quite a bit the definition of the fixmap. There
are not many use of the FIXMAP within the code and I think it would
simply be better to abstract the use (or removing it when possible) and
avoid defining FIXMAP_ADDR() & co for MPU.
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.c...@arm.com>
---
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
I can't find any change of mm.c in this series. So surely this will
break the build?
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 */
Cheers,
--
Julien Grall
