Hi Hari,
On 20/06/2025 10:49, Hari Limaye wrote:
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From: Penny Zheng <penny.zh...@arm.com>
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.zh...@arm.com>
Signed-off-by: Wei Chen <wei.c...@arm.com>
Signed-off-by: Luca Fancellu <luca.fance...@arm.com>
Signed-off-by: Hari Limaye <hari.lim...@arm.com>
---
xen/arch/arm/include/asm/mpu.h | 2 +
xen/arch/arm/include/asm/mpu/cpregs.h | 4 ++
xen/arch/arm/mpu/mm.c | 71 ++++++++++++++++++++++++++-
3 files changed, 75 insertions(+), 2 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 1de28d2120..23230936f7 100644
--- a/xen/arch/arm/mpu/mm.c
+++ b/xen/arch/arm/mpu/mm.c
@@ -199,6 +199,42 @@ 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: 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);
NIT.
These 2 lines we can move before the if { ..}. So that the region is
zeroed even if the region is disabled. This will add a small overhead,
but we will be sure that the region is zeroed whenever it is disabled.
+
+ /*
+ * 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 */
+ uint64_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.
@@ -217,11 +253,11 @@ static int xen_mpumap_update_entry(paddr_t base, paddr_t
limit,
ASSERT(spin_is_locked(&xen_mpumap_lock));
rc = mpumap_contain_region(xen_mpumap, max_mpu_regions, base, limit,
&idx);
- if ( (rc < 0) || (rc > MPUMAP_REGION_NOTFOUND) )
+ if ( rc < 0 )
return -EINVAL;
/* We are inserting a mapping => Create new region. */
- if ( flags & _PAGE_PRESENT )
+ if ( (flags & _PAGE_PRESENT) && (MPUMAP_REGION_NOTFOUND == rc) )
Same question in this patch , why do we need to check for _PAGE_PRESENT.
Can't we just rely on MPUMAP_REGION_XXX ?
{
rc = xen_mpumap_alloc_entry(&idx);
if ( rc )
@@ -232,6 +268,22 @@ static int xen_mpumap_update_entry(paddr_t base, paddr_t
limit,
write_protection_region(&xen_mpumap[idx], idx);
}
+ if ( !(flags & _PAGE_PRESENT) && (rc >= MPUMAP_REGION_FOUND) )
+ {
+ /*
+ * Currently, 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.
+ */
+ if ( MPUMAP_REGION_INCLUSIVE == rc )
+ {
+ region_printk("mpu: part-region removing is not supported\n");
+ return -EINVAL;
+ }
NIT.
Can we keep this ^^^ outside of the outer if condition ie "if ( !(flags
& _PAGE_PRESENT) && (rc >= MPUMAP_REGION_FOUND) )" ?
+
+ disable_mpu_region_from_index(idx);
+ }
+
return 0;
}
@@ -261,6 +313,21 @@ 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)
+{
+ int rc;
+
+ ASSERT(IS_ALIGNED(s, PAGE_SIZE));
+ ASSERT(IS_ALIGNED(e, PAGE_SIZE));
+ ASSERT(s <= e);
Can we have these asserts in xen_mpumap_update() as well ?
+
+ rc = xen_mpumap_update(virt_to_maddr(s), virt_to_maddr(e), 0);
+ if ( !rc )
+ context_sync_mpu();
+
+ return rc;
+}
+
int map_pages_to_xen(unsigned long virt, mfn_t mfn, unsigned long nr_mfns,
unsigned int flags)
{
--
2.34.1
- Ayan
