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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] arm/mpu: Provide access to the MPU region from the C code
commit 54f34554b566b1ce6ce2a673fabb8ef60ff05cc6
Author: Luca Fancellu <luca.fancellu@xxxxxxx>
AuthorDate: Fri May 23 07:54:04 2025 +0100
Commit: Michal Orzel <michal.orzel@xxxxxxx>
CommitDate: Fri May 30 08:46:21 2025 +0200
arm/mpu: Provide access to the MPU region from the C code
Implement some utility functions in order to access the MPU regions
from the C world.
Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
---
xen/arch/arm/include/asm/arm64/mpu.h | 2 +
xen/arch/arm/include/asm/mpu/mm.h | 24 +++++++
xen/arch/arm/mpu/mm.c | 121 +++++++++++++++++++++++++++++++++++
3 files changed, 147 insertions(+)
diff --git a/xen/arch/arm/include/asm/arm64/mpu.h
b/xen/arch/arm/include/asm/arm64/mpu.h
index 4737868507..f0ce344e78 100644
--- a/xen/arch/arm/include/asm/arm64/mpu.h
+++ b/xen/arch/arm/include/asm/arm64/mpu.h
@@ -5,6 +5,8 @@
#ifndef __ASSEMBLY__
+#define MPU_REGION_RES0 (0xFFFFULL << 48)
+
/* Protection Region Base Address Register */
typedef union {
struct __packed {
diff --git a/xen/arch/arm/include/asm/mpu/mm.h
b/xen/arch/arm/include/asm/mpu/mm.h
index 409b4dd53d..d7950d9b4f 100644
--- a/xen/arch/arm/include/asm/mpu/mm.h
+++ b/xen/arch/arm/include/asm/mpu/mm.h
@@ -41,6 +41,30 @@ static inline struct page_info *virt_to_page(const void *v)
return mfn_to_page(mfn);
}
+/* Utility function to be used whenever MPU regions are modified */
+static inline void context_sync_mpu(void)
+{
+ /*
+ * ARM DDI 0600B.a, C1.7.1
+ * Writes to MPU registers are only guaranteed to be visible following a
+ * Context synchronization event and DSB operation.
+ */
+ dsb(sy);
+ isb();
+}
+
+/*
+ * The following API requires context_sync_mpu() after being used to modify MPU
+ * regions:
+ * - write_protection_region
+ */
+
+/* Reads the MPU region (into @pr_read) with index @sel from the HW */
+void read_protection_region(pr_t *pr_read, uint8_t sel);
+
+/* Writes the MPU region (from @pr_write) with index @sel to the HW */
+void write_protection_region(const pr_t *pr_write, uint8_t sel);
+
#endif /* __ARM_MPU_MM_H__ */
/*
diff --git a/xen/arch/arm/mpu/mm.c b/xen/arch/arm/mpu/mm.c
index 2f31b7b787..9c5789cdf1 100644
--- a/xen/arch/arm/mpu/mm.c
+++ b/xen/arch/arm/mpu/mm.c
@@ -8,6 +8,8 @@
#include <xen/sizes.h>
#include <xen/types.h>
#include <asm/mpu.h>
+#include <asm/mpu/mm.h>
+#include <asm/sysregs.h>
struct page_info *frame_table;
@@ -26,6 +28,35 @@ DECLARE_BITMAP(xen_mpumap_mask, MAX_MPU_REGION_NR) \
/* EL2 Xen MPU memory region mapping table. */
pr_t __cacheline_aligned __section(".data") xen_mpumap[MAX_MPU_REGION_NR];
+#ifdef CONFIG_ARM_64
+/*
+ * The following are needed for the cases: GENERATE_WRITE_PR_REG_CASE
+ * and GENERATE_READ_PR_REG_CASE with num==0
+ */
+#define PRBAR0_EL2 PRBAR_EL2
+#define PRLAR0_EL2 PRLAR_EL2
+
+#define PRBAR_EL2_(n) PRBAR##n##_EL2
+#define PRLAR_EL2_(n) PRLAR##n##_EL2
+
+#endif /* CONFIG_ARM_64 */
+
+#define GENERATE_WRITE_PR_REG_CASE(num, pr) \
+ case num: \
+ { \
+ WRITE_SYSREG(pr->prbar.bits & ~MPU_REGION_RES0, PRBAR_EL2_(num)); \
+ WRITE_SYSREG(pr->prlar.bits & ~MPU_REGION_RES0, PRLAR_EL2_(num)); \
+ break; \
+ }
+
+#define GENERATE_READ_PR_REG_CASE(num, pr) \
+ case num: \
+ { \
+ pr->prbar.bits = READ_SYSREG(PRBAR_EL2_(num)); \
+ pr->prlar.bits = READ_SYSREG(PRLAR_EL2_(num)); \
+ break; \
+ }
+
static void __init __maybe_unused build_assertions(void)
{
/*
@@ -36,6 +67,96 @@ static void __init __maybe_unused build_assertions(void)
BUILD_BUG_ON(PAGE_SIZE != SZ_4K);
}
+#ifdef CONFIG_ARM_64
+/*
+ * Armv8-R supports direct access and indirect access to the MPU regions
through
+ * registers:
+ * - indirect access involves changing the MPU region selector, issuing an isb
+ * barrier and accessing the selected region through specific registers
+ * - direct access involves accessing specific registers that point to
+ * specific MPU regions, without changing the selector, avoiding the use of
+ * a barrier.
+ * For Arm64 the PR{B,L}AR_ELx (for n=0) and PR{B,L}AR<n>_ELx (for n=1..15) are
+ * used for the direct access to the regions selected by
+ * PRSELR_EL2.REGION<7:4>:n, so 16 regions can be directly accessed when the
+ * selector is a multiple of 16, giving access to all the supported memory
+ * regions.
+ */
+static void prepare_selector(uint8_t *sel)
+{
+ uint8_t cur_sel = *sel;
+
+ /*
+ * {read,write}_protection_region works using the direct access to the
0..15
+ * regions, so in order to save the isb() overhead, change the PRSELR_EL2
+ * only when needed, so when the upper 4 bits of the selector will change.
+ */
+ cur_sel &= 0xF0U;
+ if ( READ_SYSREG(PRSELR_EL2) != cur_sel )
+ {
+ WRITE_SYSREG(cur_sel, PRSELR_EL2);
+ isb();
+ }
+ *sel &= 0xFU;
+}
+
+void read_protection_region(pr_t *pr_read, uint8_t sel)
+{
+ prepare_selector(&sel);
+
+ switch ( sel )
+ {
+ GENERATE_READ_PR_REG_CASE(0, pr_read);
+ GENERATE_READ_PR_REG_CASE(1, pr_read);
+ GENERATE_READ_PR_REG_CASE(2, pr_read);
+ GENERATE_READ_PR_REG_CASE(3, pr_read);
+ GENERATE_READ_PR_REG_CASE(4, pr_read);
+ GENERATE_READ_PR_REG_CASE(5, pr_read);
+ GENERATE_READ_PR_REG_CASE(6, pr_read);
+ GENERATE_READ_PR_REG_CASE(7, pr_read);
+ GENERATE_READ_PR_REG_CASE(8, pr_read);
+ GENERATE_READ_PR_REG_CASE(9, pr_read);
+ GENERATE_READ_PR_REG_CASE(10, pr_read);
+ GENERATE_READ_PR_REG_CASE(11, pr_read);
+ GENERATE_READ_PR_REG_CASE(12, pr_read);
+ GENERATE_READ_PR_REG_CASE(13, pr_read);
+ GENERATE_READ_PR_REG_CASE(14, pr_read);
+ GENERATE_READ_PR_REG_CASE(15, pr_read);
+ default:
+ BUG(); /* Can't happen */
+ break;
+ }
+}
+
+void write_protection_region(const pr_t *pr_write, uint8_t sel)
+{
+ prepare_selector(&sel);
+
+ switch ( sel )
+ {
+ GENERATE_WRITE_PR_REG_CASE(0, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(1, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(2, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(3, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(4, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(5, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(6, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(7, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(8, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(9, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(10, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(11, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(12, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(13, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(14, pr_write);
+ GENERATE_WRITE_PR_REG_CASE(15, pr_write);
+ default:
+ BUG(); /* Can't happen */
+ break;
+ }
+}
+#endif /* CONFIG_ARM_64 */
+
void __init setup_mm(void)
{
BUG_ON("unimplemented");
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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