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Re: [PATCH v2 26/40] xen/mpu: destroy an existing entry in Xen MPU memory mapping table
Hi Penny,
On 13/01/2023 05:28, Penny Zheng wrote:
This commit expands xen_mpumap_update/xen_mpumap_update_entry to include
destroying an existing entry.
We define a new helper "control_xen_mpumap_region_from_index" to enable/disable
the MPU region based on index. If region is within [0, 31], we could quickly
disable the MPU region through PRENR_EL2 which provides direct access to the
PRLAR_EL2.EN bits of EL2 MPU regions.
Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
---
xen/arch/arm/include/asm/arm64/mpu.h | 20 ++++++
xen/arch/arm/include/asm/arm64/sysregs.h | 3 +
xen/arch/arm/mm_mpu.c | 77 ++++++++++++++++++++++--
3 files changed, 95 insertions(+), 5 deletions(-)
diff --git a/xen/arch/arm/include/asm/arm64/mpu.h
b/xen/arch/arm/include/asm/arm64/mpu.h
index 0044bbf05d..c1dea1c8e9 100644
--- a/xen/arch/arm/include/asm/arm64/mpu.h
+++ b/xen/arch/arm/include/asm/arm64/mpu.h
@@ -16,6 +16,8 @@
*/
#define ARM_MAX_MPU_MEMORY_REGIONS 255
+#define MPU_PRENR_BITS 32
+
/* Access permission attributes. */
/* Read/Write at EL2, No Access at EL1/EL0. */
#define AP_RW_EL2 0x0
@@ -132,6 +134,24 @@ typedef struct {
_pr->prlar.reg.en; \
})
+/*
+ * Access to get base address of MPU protection region(pr_t).
+ * The base address shall be zero extended.
+ */
+#define pr_get_base(pr) ({ \
+ pr_t *_pr = pr; \
+ (uint64_t)_pr->prbar.reg.base << MPU_REGION_SHIFT; \
+})
Can this be a static inline?
+
+/*
+ * Access to get limit address of MPU protection region(pr_t).
+ * The limit address shall be concatenated with 0x3f.
+ */
+#define pr_get_limit(pr) ({ \
+ pr_t *_pr = pr; \
+ (uint64_t)((_pr->prlar.reg.limit << MPU_REGION_SHIFT) | 0x3f); \
+})
Same.
+
#endif /* __ASSEMBLY__ */
#endif /* __ARM64_MPU_H__ */
diff --git a/xen/arch/arm/include/asm/arm64/sysregs.h
b/xen/arch/arm/include/asm/arm64/sysregs.h
index aca9bca5b1..c46daf6f69 100644
--- a/xen/arch/arm/include/asm/arm64/sysregs.h
+++ b/xen/arch/arm/include/asm/arm64/sysregs.h
@@ -505,6 +505,9 @@
/* MPU Type registers encode */
#define MPUIR_EL2 S3_4_C0_C0_4
+/* MPU Protection Region Enable Register encode */
+#define PRENR_EL2 S3_4_C6_C1_1
+
#endif
/* Access to system registers */
diff --git a/xen/arch/arm/mm_mpu.c b/xen/arch/arm/mm_mpu.c
index d2e19e836c..3a0d110b13 100644
--- a/xen/arch/arm/mm_mpu.c
+++ b/xen/arch/arm/mm_mpu.c
@@ -385,6 +385,45 @@ static int mpumap_contain_region(pr_t *mpu, uint64_t
nr_regions,
return MPUMAP_REGION_FAILED;
}
+/* Disable or enable EL2 MPU memory region at index #index */
+static void control_mpu_region_from_index(uint64_t index, bool enable)
+{
+ pr_t region;
+
+ access_protection_region(true, ®ion, NULL, index);
+ if ( (region_is_valid(®ion) && enable) ||
+ (!region_is_valid(®ion) && !enable) )
You could write:
!(region_is_valid(®ion) ^ enable)
+ {
+ printk(XENLOG_WARNING
+ "mpu: MPU memory region[%lu] is already %s\n", index,
+ enable ? "enabled" : "disabled");
+ return;
+ }
+
+ /*
+ * ARM64v8R provides PRENR_EL2 to have direct access to the
+ * PRLAR_EL2.EN bits of EL2 MPU regions from 0 to 31.
+ */
+ if ( index < MPU_PRENR_BITS )
+ {
+ uint64_t orig, after;
+
+ orig = READ_SYSREG(PRENR_EL2);
+ if ( enable )
+ /* Set respective bit */
+ after = orig | (1UL << index);
+ else
+ /* Clear respective bit */
+ after = orig & (~(1UL << index));
+ WRITE_SYSREG(after, PRENR_EL2);
Don't you need an isb (or similar) to ensure this is visible before...
+ }
+ else
+ {
+ region.prlar.reg.en = enable ? 1 : 0;
+ access_protection_region(false, NULL, (const pr_t*)®ion, index);
+ }
+}
+
/*
* Update an entry at the index @idx.
* @base: base address
@@ -449,6 +488,30 @@ static int xen_mpumap_update_entry(paddr_t base, paddr_t
limit,
if ( system_state <= SYS_STATE_active )
update_boot_xen_mpumap_idx(idx);
}
+ else
+ {
+ /*
+ * Currently, we only support destroying a *WHOLE* MPU memory region,
+ * part-region removing is not supported, as in worst case, it will
+ * lead to two fragments in result after destroying.
+ * part-region removing will be introduced only when actual usage
+ * comes.
+ */
+ if ( rc == MPUMAP_REGION_INCLUSIVE )
+ {
+ region_printk("mpu: part-region removing is not supported\n");
+ return -EINVAL;
+ }
+
+ /* We are removing the region */
+ if ( rc != MPUMAP_REGION_FOUND )
+ return -EINVAL;
+
+ control_mpu_region_from_index(idx, false);
+
+ /* Clear the according MPU memory region entry.*/
+ memset(&xen_mpumap[idx], 0, sizeof(pr_t));
... zeroing the entry? Also, you could use memzero() here.
+ }
return 0;
}
@@ -589,6 +652,15 @@ static void __init map_mpu_memory_section_on_boot(enum
mpu_section_info type,
}
}
+int destroy_xen_mappings(unsigned long s, unsigned long e)
+{
+ ASSERT(IS_ALIGNED(s, PAGE_SIZE));
+ ASSERT(IS_ALIGNED(e, PAGE_SIZE));
+ ASSERT(s <= e);
+
+ return xen_mpumap_update(s, e, 0);
+}
+
/*
* System RAM is statically partitioned into different functionality
* section in Device Tree, including static xenheap, guest memory
@@ -656,11 +728,6 @@ void *ioremap(paddr_t pa, size_t len)
return NULL;
}
-int destroy_xen_mappings(unsigned long s, unsigned long e)
-{
- return -ENOSYS;
-}
-
int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int flags)
{
return -ENOSYS;
Cheers,
--
Julien Grall
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