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Re: [PATCH v5 2/3] xen/arm32: Create the same boot-time MPU regions as arm64
- To: "Orzel, Michal" <michal.orzel@xxxxxxx>, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Ayan Kumar Halder <ayankuma@xxxxxxx>
- Date: Fri, 11 Apr 2025 10:06:21 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Fri, 11 Apr 2025 09:06:38 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi,
On 08/04/2025 10:13, Orzel, Michal wrote:
On 07/04/2025 20:44, Ayan Kumar Halder wrote:
We have created the same boot-time MPU protection regions as Armv8-R AArch64.
Also, we have defined *_PRBAR macros for arm32. The only difference from
arm64 is that XN is 1-bit for arm32.
The macros have been defined in mpu/cpregs.h.
NIT: Describe your changes in imperative mood
Also defined WRITE_SYSREG_ASM() to write to system registers in assembly.
Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
---
Changes from
v1 -
1. enable_mpu() now sets HMAIR{0,1} registers. This is similar to what is
being done in enable_mmu(). All the mm related configurations happen in this
function.
2. Fixed some typos.
v2 -
1. Include the common prepare_xen_region.inc in head.S.
2. Define LOAD_SYSREG()/STORE_SYSREG() for arm32.
v3 -
1. Rename STORE_SYSREG() as WRITE_SYSREG_ASM()
2. enable_boot_cpu_mm() is defined in head.S
v4 -
1. *_PRBAR is moved to arm32/sysregs.h.
2. MPU specific CP15 system registers are defined in mpu/cpregs.h.
xen/arch/arm/arm32/Makefile | 1 +
xen/arch/arm/arm32/mpu/Makefile | 1 +
xen/arch/arm/arm32/mpu/head.S | 101 +++++++++++++++++++++++
xen/arch/arm/include/asm/arm32/sysregs.h | 7 ++
xen/arch/arm/include/asm/cpregs.h | 4 +
xen/arch/arm/include/asm/mpu/cpregs.h | 24 ++++++
6 files changed, 138 insertions(+)
create mode 100644 xen/arch/arm/arm32/mpu/Makefile
create mode 100644 xen/arch/arm/arm32/mpu/head.S
create mode 100644 xen/arch/arm/include/asm/mpu/cpregs.h
diff --git a/xen/arch/arm/arm32/Makefile b/xen/arch/arm/arm32/Makefile
index 40a2b4803f..537969d753 100644
--- a/xen/arch/arm/arm32/Makefile
+++ b/xen/arch/arm/arm32/Makefile
@@ -1,5 +1,6 @@
obj-y += lib/
obj-$(CONFIG_MMU) += mmu/
+obj-$(CONFIG_MPU) += mpu/
obj-$(CONFIG_EARLY_PRINTK) += debug.o
obj-y += domctl.o
diff --git a/xen/arch/arm/arm32/mpu/Makefile b/xen/arch/arm/arm32/mpu/Makefile
new file mode 100644
index 0000000000..3340058c08
--- /dev/null
+++ b/xen/arch/arm/arm32/mpu/Makefile
@@ -0,0 +1 @@
+obj-y += head.o
diff --git a/xen/arch/arm/arm32/mpu/head.S b/xen/arch/arm/arm32/mpu/head.S
new file mode 100644
index 0000000000..84e9f1f8ec
--- /dev/null
+++ b/xen/arch/arm/arm32/mpu/head.S
@@ -0,0 +1,101 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Start-of-day code for an Armv8-R MPU system.
That's exactly the same text as for Aarch64. At least write Armv8A-R-AArch32.
Ack
+ */
+
+#include <asm/arm32/macros.h>
+#include <asm/mpu/common.inc>
+#include <asm/page.h>
+
+/*
+ * Set up the memory attribute type tables and enable EL2 MPU and data cache.
+ * If the Background region is enabled, then the MPU uses the default memory
+ * map as the Background region for generating the memory
+ * attributes when MPU is disabled.
+ * Since the default memory map of the Armv8-R AArch32 architecture is
+ * IMPLEMENTATION DEFINED, we intend to turn off the Background region here.
+ *
+ * Clobbers r0 - r1
+ */
+FUNC_LOCAL(enable_mpu)
+ /* Set up memory attribute type tables */
+ mov_w r0, MAIR0VAL
+ mov_w r1, MAIR1VAL
+ mcr CP32(r0, HMAIR0)
+ mcr CP32(r1, HMAIR1)
Is there really a need to do these 2 writes one after another?
Why can't we use only r0 and save one clobbered reg?
mov_w r0, MAIR0VAL
mcr CP32(r0, HMAIR0)
mov_w r0, MAIR1VAL
mcr CP32(r0, HMAIR1)
I just copied it as it is from head.S. :) I will change it in v6.
+
+ mrc CP32(r0, HSCTLR)
+ bic r0, r0, #SCTLR_ELx_BR /* Disable Background region */
+ orr r0, r0, #SCTLR_Axx_ELx_M /* Enable MPU */
+ orr r0, r0, #SCTLR_Axx_ELx_C /* Enable D-cache */
+ mcr CP32(r0, HSCTLR)
+ isb
+
+ ret
+END(enable_mpu)
+
+/*
+ * Maps the various sections of Xen (described in xen.lds.S) as different MPU
+ * regions.
+ *
+ * Clobbers r0 - r5
+ *
+ */
+FUNC(enable_boot_cpu_mm)
+ /* Get the number of regions specified in MPUIR_EL2 */
+ mrc CP32(r5, MPUIR_EL2)
+ and r5, r5, #NUM_MPU_REGIONS_MASK
+
+ /* x0: region sel */
+ mov r0, #0
+ /* Xen text section. */
+ mov_w r1, _stext
+ mov_w r2, _etext
+ prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_TEXT_PRBAR
+
+ /* Xen read-only data section. */
+ mov_w r1, _srodata
+ mov_w r2, _erodata
+ prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_RO_PRBAR
+
+ /* Xen read-only after init and data section. (RW data) */
+ mov_w r1, __ro_after_init_start
+ mov_w r2, __init_begin
+ prepare_xen_region r0, r1, r2, r3, r4, r5
+
+ /* Xen code section. */
+ mov_w r1, __init_begin
+ mov_w r2, __init_data_begin
+ prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_TEXT_PRBAR
+
+ /* Xen data and BSS section. */
+ mov_w r1, __init_data_begin
+ mov_w r2, __bss_end
+ prepare_xen_region r0, r1, r2, r3, r4, r5
+
+#ifdef CONFIG_EARLY_PRINTK
+ /* Xen early UART section. */
+ mov_w r1, CONFIG_EARLY_UART_BASE_ADDRESS
+ mov_w r2, (CONFIG_EARLY_UART_BASE_ADDRESS + CONFIG_EARLY_UART_SIZE)
+ prepare_xen_region r0, r1, r2, r3, r4, r5, attr_prbar=REGION_DEVICE_PRBAR,
attr_prlar=REGION_DEVICE_PRLAR
+#endif
+
+ b enable_mpu
+END(enable_boot_cpu_mm)
+
+/*
+ * We don't yet support secondary CPUs bring-up. Implement a dummy helper to
+ * please the common code.
+ */
+FUNC(enable_secondary_cpu_mm)
+ PRINT("- SMP not enabled yet -\r\n")
+1: wfe
+ b 1b
+END(enable_secondary_cpu_mm)
+
+/*
+ * Local variables:
+ * mode: ASM
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/arm/include/asm/arm32/sysregs.h
b/xen/arch/arm/include/asm/arm32/sysregs.h
index 22871999af..a90d1610a1 100644
--- a/xen/arch/arm/include/asm/arm32/sysregs.h
+++ b/xen/arch/arm/include/asm/arm32/sysregs.h
@@ -20,6 +20,13 @@
* uses r0 as a placeholder register. */
#define CMD_CP32(name...) "mcr " __stringify(CP32(r0, name)) ";"
+#define REGION_TEXT_PRBAR 0x18 /* SH=11 AP=10 XN=0 */
+#define REGION_RO_PRBAR 0x1D /* SH=11 AP=10 XN=1 */
+#define REGION_DATA_PRBAR 0x19 /* SH=11 AP=00 XN=1 */
+#define REGION_DEVICE_PRBAR 0x11 /* SH=10 AP=00 XN=1 */
+
+#define WRITE_SYSREG_ASM(v, name) mcr CP32(v, name)
Same comment as for previous patch.
Ack.
+
#ifndef __ASSEMBLY__
/* C wrappers */
diff --git a/xen/arch/arm/include/asm/cpregs.h
b/xen/arch/arm/include/asm/cpregs.h
index aec9e8f329..6019a2cbdd 100644
--- a/xen/arch/arm/include/asm/cpregs.h
+++ b/xen/arch/arm/include/asm/cpregs.h
@@ -1,6 +1,10 @@
#ifndef __ASM_ARM_CPREGS_H
#define __ASM_ARM_CPREGS_H
+#ifdef CONFIG_MPU
NIT: Do we really need to protect this include? I thought we do the ifdefery if
we need to include either mmu or mpu. Here we don't have a choice and afaict
there's nothing problematic in mpu/cpregs.h
Ack.
+#include <asm/mpu/cpregs.h>
+#endif
+
/*
* AArch32 Co-processor registers.
*
diff --git a/xen/arch/arm/include/asm/mpu/cpregs.h
b/xen/arch/arm/include/asm/mpu/cpregs.h
new file mode 100644
index 0000000000..6b20c7ceae
--- /dev/null
+++ b/xen/arch/arm/include/asm/mpu/cpregs.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_ARM_MPU_CPREGS_H
+#define __ASM_ARM_MPU_CPREGS_H
+
+/* CP15 CR0: MPU Type Register */
+#define HMPUIR p15,4,c0,c0,4
+
+/* CP15 CR6: MPU Protection Region Base/Limit/Select Address Register */
+#define HPRSELR p15,4,c6,c2,1
+#define PRBAR_EL2 p15,4,c6,c3,0
+#define PRLAR_EL2 p15,4,c6,c8,1
+
+#define MPUIR_EL2 HMPUIR
+#define PRSELR_EL2 HPRSELR
AFAIK, these macros are there to use AArch64 sysreg names in common code when
compiling Arm32. This would mean they should be protected with #ifdef
CONFIG_ARM_32.
In the case of Arm64, the MPU system registers are defined by the
compiler. So, these definitions are overridden.
I will enclose this within CONFIG_ARM_32 for better readability.
@Luca - I will keep your R-b unless you object. The changes are mostly
style related. :)
- Ayan
~Michal
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