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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] arm/mpu: Destroy an existing entry in Xen MPU memory mapping table
commit 81819566989d9478daa8889c5c56f013b4073eda
Author: Penny Zheng <Penny.Zheng@xxxxxxx>
AuthorDate: Mon Jul 21 09:31:45 2025 +0100
Commit: Michal Orzel <michal.orzel@xxxxxxx>
CommitDate: Wed Jul 23 09:51:50 2025 +0200
arm/mpu: Destroy an existing entry in Xen MPU memory mapping table
This commit expands xen_mpumap_update/xen_mpumap_update_entry to include
destroying an existing entry.
We define a new helper "disable_mpu_region_from_index" to 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.
Rignt now, we only support destroying a *WHOLE* MPU memory region,
part-region removing is not supported, as in worst case, it will
leave two fragments behind.
Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Signed-off-by: Hari Limaye <hari.limaye@xxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
---
xen/arch/arm/include/asm/mpu.h | 2 +
xen/arch/arm/include/asm/mpu/cpregs.h | 4 ++
xen/arch/arm/mpu/mm.c | 95 +++++++++++++++++++++++++++++++----
3 files changed, 92 insertions(+), 9 deletions(-)
diff --git a/xen/arch/arm/include/asm/mpu.h b/xen/arch/arm/include/asm/mpu.h
index 63560c613b..5053edaf63 100644
--- a/xen/arch/arm/include/asm/mpu.h
+++ b/xen/arch/arm/include/asm/mpu.h
@@ -23,6 +23,8 @@
#define NUM_MPU_REGIONS_MASK (NUM_MPU_REGIONS - 1)
#define MAX_MPU_REGION_NR NUM_MPU_REGIONS_MASK
+#define PRENR_MASK GENMASK(31, 0)
+
#ifndef __ASSEMBLY__
/*
diff --git a/xen/arch/arm/include/asm/mpu/cpregs.h
b/xen/arch/arm/include/asm/mpu/cpregs.h
index bb15e02df6..9f3b32acd7 100644
--- a/xen/arch/arm/include/asm/mpu/cpregs.h
+++ b/xen/arch/arm/include/asm/mpu/cpregs.h
@@ -6,6 +6,9 @@
/* CP15 CR0: MPU Type Register */
#define HMPUIR p15,4,c0,c0,4
+/* CP15 CR6: Protection Region Enable Register */
+#define HPRENR p15,4,c6,c1,1
+
/* CP15 CR6: MPU Protection Region Base/Limit/Select Address Register */
#define HPRSELR p15,4,c6,c2,1
#define HPRBAR p15,4,c6,c3,0
@@ -82,6 +85,7 @@
/* Alphabetically... */
#define MPUIR_EL2 HMPUIR
#define PRBAR_EL2 HPRBAR
+#define PRENR_EL2 HPRENR
#define PRLAR_EL2 HPRLAR
#define PRSELR_EL2 HPRSELR
#endif /* CONFIG_ARM_32 */
diff --git a/xen/arch/arm/mpu/mm.c b/xen/arch/arm/mpu/mm.c
index 429ce50802..c6891607ec 100644
--- a/xen/arch/arm/mpu/mm.c
+++ b/xen/arch/arm/mpu/mm.c
@@ -189,6 +189,42 @@ static int xen_mpumap_alloc_entry(uint8_t *idx)
return 0;
}
+/*
+ * Disable and remove an MPU region from the data structure and MPU registers.
+ *
+ * @param index Index of the MPU region to be disabled.
+ */
+static void disable_mpu_region_from_index(uint8_t index)
+{
+ ASSERT(spin_is_locked(&xen_mpumap_lock));
+ ASSERT(index != INVALID_REGION_IDX);
+
+ if ( !region_is_valid(&xen_mpumap[index]) )
+ {
+ printk(XENLOG_WARNING
+ "MPU memory region[%u] is already disabled\n", index);
+ return;
+ }
+
+ /* Zeroing the region will also zero the region enable */
+ memset(&xen_mpumap[index], 0, sizeof(pr_t));
+ clear_bit(index, xen_mpumap_mask);
+
+ /*
+ * Both Armv8-R AArch64 and AArch32 have direct access to the enable bit
for
+ * MPU regions numbered from 0 to 31.
+ */
+ if ( (index & PRENR_MASK) != 0 )
+ {
+ /* Clear respective bit */
+ register_t val = READ_SYSREG(PRENR_EL2) & (~(1UL << index));
+
+ WRITE_SYSREG(val, PRENR_EL2);
+ }
+ else
+ write_protection_region(&xen_mpumap[index], index);
+}
+
/*
* Update the entry in the MPU memory region mapping table (xen_mpumap) for the
* given memory range and flags, creating one if none exists.
@@ -201,27 +237,59 @@ static int xen_mpumap_alloc_entry(uint8_t *idx)
static int xen_mpumap_update_entry(paddr_t base, paddr_t limit,
unsigned int flags)
{
+ bool flags_has_page_present;
uint8_t idx;
int rc;
ASSERT(spin_is_locked(&xen_mpumap_lock));
- /* Currently only region creation is supported. */
- if ( !(flags & _PAGE_PRESENT) )
+ rc = mpumap_contains_region(xen_mpumap, max_mpu_regions, base, limit,
&idx);
+ if ( rc < 0 )
return -EINVAL;
- rc = mpumap_contains_region(xen_mpumap, max_mpu_regions, base, limit,
&idx);
- if ( rc != MPUMAP_REGION_NOTFOUND )
+ flags_has_page_present = flags & _PAGE_PRESENT;
+
+ /* Currently we don't support modifying an existing entry. */
+ if ( flags_has_page_present && (rc >= MPUMAP_REGION_FOUND) )
+ {
+ printk("Modifying an existing entry is not supported\n");
return -EINVAL;
+ }
+
+ /*
+ * Currently, we only support removing/modifying a *WHOLE* MPU memory
+ * region. Part-region removal/modification is not supported as in the
worst
+ * case it will leave two/three fragments behind.
+ */
+ if ( rc == MPUMAP_REGION_INCLUSIVE )
+ {
+ printk("Part-region removal/modification is not supported\n");
+ return -EINVAL;
+ }
/* We are inserting a mapping => Create new region. */
- rc = xen_mpumap_alloc_entry(&idx);
- if ( rc )
- return -ENOENT;
+ if ( flags_has_page_present && (MPUMAP_REGION_NOTFOUND == rc) )
+ {
+ rc = xen_mpumap_alloc_entry(&idx);
+ if ( rc )
+ return -ENOENT;
+
+ xen_mpumap[idx] = pr_of_addr(base, limit, flags);
- xen_mpumap[idx] = pr_of_addr(base, limit, flags);
+ write_protection_region(&xen_mpumap[idx], idx);
+ }
+
+ /* Removing a mapping */
+ if ( !flags_has_page_present )
+ {
+ if ( rc == MPUMAP_REGION_NOTFOUND )
+ {
+ printk("Cannot remove an entry that does not exist\n");
+ return -EINVAL;
+ }
- write_protection_region(&xen_mpumap[idx], idx);
+ disable_mpu_region_from_index(idx);
+ }
return 0;
}
@@ -261,6 +329,15 @@ int xen_mpumap_update(paddr_t base, paddr_t limit,
unsigned int flags)
return rc;
}
+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);
+}
+
int map_pages_to_xen(unsigned long virt, mfn_t mfn, unsigned long nr_mfns,
unsigned int flags)
{
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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