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Re: [PATCH v3 27/52] xen/mpu: introduce setup_mm_mappings
- To: Julien Grall <julien@xxxxxxx>, Penny Zheng <Penny.Zheng@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Ayan Kumar Halder <ayankuma@xxxxxxx>
- Date: Thu, 29 Jun 2023 15:50:04 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Wei Chen <wei.chen@xxxxxxx>
- Delivery-date: Thu, 29 Jun 2023 14:50:18 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 29/06/2023 15:29, Julien Grall wrote:
Hi,
On 29/06/2023 15:05, Ayan Kumar Halder wrote:
On 26/06/2023 04:34, Penny Zheng wrote:
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Function setup_pagetables is responsible for boot-time pagetable setup
in MMU system at C world.
In MPU system, as we have already built up start-of-day Xen MPU memory
region mapping in assembly boot-time, here we only need to do a few
memory management data initializtion, including reading the number of
maximum MPU regions supported by the EL2 MPU, and setting the according
bitfield for regions enabled in assembly boot-time, in bitmap
xen_mpumap_mask.
This bitmap xen_mpumap_mask is responsible for recording the usage
of EL2 MPU
memory regions.
In order to keep only one codeflow in arm/setup.c, setup_mm_mappings
, with a more generic name, is introduced to replace setup_pagetables.
Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
---
v3:
- introduce bitmap xen_mpumap_mask for dynamic allocation on MPU
regions
---
xen/arch/arm/include/asm/arm64/mpu.h | 1 +
xen/arch/arm/include/asm/arm64/sysregs.h | 3 +++
xen/arch/arm/include/asm/mm.h | 4 ++--
xen/arch/arm/mmu/mm.c | 7 +++++-
xen/arch/arm/mpu/mm.c | 30
++++++++++++++++++++++++
xen/arch/arm/setup.c | 2 +-
6 files changed, 43 insertions(+), 4 deletions(-)
diff --git a/xen/arch/arm/include/asm/arm64/mpu.h
b/xen/arch/arm/include/asm/arm64/mpu.h
index 6ec2c10b14..407fec66c9 100644
--- a/xen/arch/arm/include/asm/arm64/mpu.h
+++ b/xen/arch/arm/include/asm/arm64/mpu.h
@@ -19,6 +19,7 @@
* or it needs adjustment.
*/
#define REGION_UART_SEL 0x07
+#define MPUIR_REGION_MASK ((_AC(1, UL) << 8) - 1)
May be this is simpler to read
#define MPUIR_REGION_MASK _AC(0xFF, UL)
Also, you can move it to xen/arch/arm/include/asm/mpu.h as it is
common between R52 and R82.
I would actually prefer if we use GENMASK(...).
[...]
diff --git a/xen/arch/arm/mpu/mm.c b/xen/arch/arm/mpu/mm.c
index fb6bb721b1..e06a6e5810 100644
--- a/xen/arch/arm/mpu/mm.c
+++ b/xen/arch/arm/mpu/mm.c
@@ -20,6 +20,7 @@
*/
#include <xen/init.h>
+#include <xen/mm.h>
#include <xen/page-size.h>
#include <asm/arm64/mpu.h>
@@ -27,6 +28,35 @@
pr_t __aligned(PAGE_SIZE) __section(".data.page_aligned")
xen_mpumap[ARM_MAX_MPU_MEMORY_REGIONS];
+/* Maximum number of supported MPU memory regions by the EL2 MPU. */
+uint8_t __ro_after_init max_xen_mpumap;
+
+/*
+ * Bitmap xen_mpumap_mask is to record the usage of EL2 MPU memory
regions.
+ * Bit 0 represents MPU memory region 0, bit 1 represents MPU memory
+ * region 1, ..., and so on.
+ * If a MPU memory region gets enabled, set the according bit to 1.
+ */
+static DECLARE_BITMAP(xen_mpumap_mask, ARM_MAX_MPU_MEMORY_REGIONS);
+
+void __init setup_mm_mappings(unsigned long boot_phys_offset)
+{
+ unsigned int nr_regions = REGION_UART_SEL, i = 0;
+
+ /*
+ * MPUIR_EL2.Region[0:7] identifies the number of regions
supported by
+ * the EL2 MPU.
+ */
+ max_xen_mpumap = (uint8_t)(READ_SYSREG(MPUIR_EL2) &
MPUIR_REGION_MASK);
NIT:- You may dop "& MPUIR_REGION_MASK " as the other bits are RES0
From the Arm Arm (look for the definition of RES0 in the glossary):
"
To preserve forward compatibility, software:
• Must not rely on the bit reading as 0.
• Must use an SBZP policy to write to the bit.
"
So we should not drop "& MPUIR_REGION_MASK".
Yes, you are correct.
Penny, please disregard my NIT.
- Ayan
Cheers,
|
