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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v4 8/8] xen/arm32: head: Use a page mapping for the 1:1 mapping in create_page_tables()
At the moment the function create_page_tables() will use 1GB/2MB
mapping for the identity mapping. As we don't know what is present
before and after Xen in memory, we may end up to map
device/reserved-memory with cacheable memory. This may result to
mismatched attributes as other users may access the same region
differently.
To prevent any issues, we should only map the strict minimum in the
1:1 mapping. A check in xen.lds.S already guarantees anything
necessary for turning on the MMU fits in a page (at the moment 4K).
As only one page will be mapped for the 1:1 mapping, it is necessary
to pre-allocate a page for the 3rd level table.
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
Changes in v4:
- Use XEN_{FIRST, SECOND}_SLOT rather than hardcoded value
- Don't pre-link the page-tables for the 1:1 mapping
Changes in v3:
- Patch added
---
xen/arch/arm/arm32/head.S | 121 +++++++++++++++++++---------------------------
xen/arch/arm/mm.c | 2 +-
2 files changed, 50 insertions(+), 73 deletions(-)
diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
index 175f0c9760..7b5109db26 100644
--- a/xen/arch/arm/arm32/head.S
+++ b/xen/arch/arm/arm32/head.S
@@ -447,73 +447,13 @@ ENDPROC(cpu_init)
* r6 : Identity map in place
*/
create_page_tables:
- /*
- * If Xen is loaded at exactly XEN_VIRT_START then we don't
- * need an additional 1:1 mapping, the virtual mapping will
- * suffice.
- */
- cmp r9, #XEN_VIRT_START
- moveq r6, #1 /* r6 := identity map now in place */
- movne r6, #0 /* r6 := identity map not yet in place */
-
- ldr r4, =boot_pgtable
- add r4, r4, r10 /* r4 := paddr (boot_pagetable) */
-
- /* Setup boot_pgtable: */
- ldr r1, =boot_second
- add r1, r1, r10 /* r1 := paddr (boot_second) */
-
- /* ... map boot_second in boot_pgtable[0] */
- orr r2, r1, #PT_UPPER(PT) /* r2:r3 := table map of boot_second */
- orr r2, r2, #PT_LOWER(PT) /* (+ rights for linear PT) */
- mov r3, #0x0
- strd r2, r3, [r4, #0] /* Map it in slot 0 */
-
- /* ... map of paddr(start) in boot_pgtable */
- lsrs r1, r9, #FIRST_SHIFT /* Offset of base paddr in boot_pgtable */
- beq 1f /* If it is in slot 0 then map in
boot_second
- * later on */
- lsl r2, r1, #FIRST_SHIFT /* Base address for 1GB mapping */
- orr r2, r2, #PT_UPPER(MEM) /* r2:r3 := section map */
- orr r2, r2, #PT_LOWER(MEM)
- lsl r1, r1, #3 /* r1 := Slot offset */
- mov r3, #0x0
- strd r2, r3, [r4, r1] /* Mapping of paddr(start) */
- mov r6, #1 /* r6 := identity map now in place */
-
-1: /* Setup boot_second: */
- ldr r4, =boot_second
- add r4, r4, r10 /* r4 := paddr (boot_second) */
-
- ldr r1, =boot_third
- add r1, r1, r10 /* r1 := paddr (boot_third) */
-
- /* ... map boot_third in boot_second[1] */
- orr r2, r1, #PT_UPPER(PT) /* r2:r3 := table map of boot_third */
- orr r2, r2, #PT_LOWER(PT) /* (+ rights for linear PT) */
- mov r3, #0x0
- strd r2, r3, [r4, #8] /* Map it in slot 1 */
-
- /* ... map of paddr(start) in boot_second */
- cmp r6, #1 /* r6 is set if already created */
- beq 1f
- lsr r2, r9, #SECOND_SHIFT /* Offset of base paddr in boot_second */
- ldr r3, =LPAE_ENTRY_MASK
- and r1, r2, r3
- cmp r1, #1
- beq virtphys_clash /* It's in slot 1, which we cannot handle
*/
-
- lsl r2, r2, #SECOND_SHIFT /* Base address for 2MB mapping */
- orr r2, r2, #PT_UPPER(MEM) /* r2:r3 := section map */
- orr r2, r2, #PT_LOWER(MEM)
- mov r3, #0x0
- lsl r1, r1, #3 /* r1 := Slot offset */
- strd r2, r3, [r4, r1] /* Mapping of paddr(start) */
- mov r6, #1 /* r6 := identity map now in place */
+ /* Prepare the page-tables for mapping Xen */
+ ldr r0, =XEN_VIRT_START
+ create_table_entry boot_pgtable, boot_second, r0, FIRST_SHIFT
+ create_table_entry boot_second, boot_third, r0, SECOND_SHIFT
/* Setup boot_third: */
-1: ldr r4, =boot_third
- add r4, r4, r10 /* r4 := paddr (boot_third) */
+ adr_l r4, boot_third, mmu=0
lsr r2, r9, #THIRD_SHIFT /* Base address for 4K mapping */
lsl r2, r2, #THIRD_SHIFT
@@ -530,16 +470,53 @@ create_page_tables:
blo 1b
/*
- * Defer fixmap and dtb mapping until after paging enabled, to
- * avoid them clashing with the 1:1 mapping.
+ * If Xen is loaded at exactly XEN_VIRT_START then we don't
+ * need an additional 1:1 mapping, the virtual mapping will
+ * suffice.
*/
+ cmp r9, #XEN_VIRT_START
+ moveq pc, lr
- /* boot pagetable setup complete */
+1:
+ /*
+ * Setup the 1:1 mapping so we can turn the MMU on. Note that
+ * only the first page of Xen will be part of the 1:1 mapping.
+ */
+
+ /*
+ * Find the first slot used. If the slot is not XEN_FIRST_SLOT,
+ * then the 1:1 mapping will use its own set of page-tables from
+ * the second level.
+ */
+ lsr r1, r9, #FIRST_SHIFT
+ mov_w r0, LPAE_ENTRY_MASK
+ and r1, r1, r0 /* r1 := first slot */
+ cmp r1, #XEN_FIRST_SLOT
+ beq 1f
+ create_table_entry boot_pgtable, boot_second_id, r9, FIRST_SHIFT
+ b link_from_second_id
+
+1:
+ /*
+ * Find the second slot used. If the slot is XEN_SECOND_SLOT, then the
+ * 1:1 mapping will use its own set of page-tables from the
+ * third level. For slot XEN_SECOND_SLOT, Xen is not yet able to handle
+ * it.
+ */
+ lsr r1, r9, #SECOND_SHIFT
+ mov_w r0, LPAE_ENTRY_MASK
+ and r1, r1, r0 /* r1 := second slot */
+ cmp r1, #XEN_SECOND_SLOT
+ beq virtphys_clash
+ create_table_entry boot_second, boot_third_id, r9, SECOND_SHIFT
+ b link_from_third_id
+
+link_from_second_id:
+ create_table_entry boot_second_id, boot_third_id, r9, SECOND_SHIFT
+link_from_third_id:
+ create_mapping_entry boot_third_id, r9, r9
+ mov pc, lr
- cmp r6, #1 /* Did we manage to create an identity
mapping ? */
- moveq pc, lr
- PRINT("Unable to build boot page tables - Failed to identity map
Xen.\r\n")
- b fail
virtphys_clash:
/* Identity map clashes with boot_third, which we cannot handle yet */
PRINT("- Unable to build boot page tables - virt and phys addresses
clash. -\r\n")
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 72ffea7472..9e0fdc39f9 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -105,9 +105,9 @@ DEFINE_BOOT_PAGE_TABLE(boot_pgtable);
#ifdef CONFIG_ARM_64
DEFINE_BOOT_PAGE_TABLE(boot_first);
DEFINE_BOOT_PAGE_TABLE(boot_first_id);
+#endif
DEFINE_BOOT_PAGE_TABLE(boot_second_id);
DEFINE_BOOT_PAGE_TABLE(boot_third_id);
-#endif
DEFINE_BOOT_PAGE_TABLE(boot_second);
DEFINE_BOOT_PAGE_TABLE(boot_third);
--
2.11.0
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