[Minios-devel] [UNIKRAFT PATCHv4 18/23] plat/kvm: arm64: Calculate pagetable size dynamically by image size

[Jia He <justin.he@xxxxxxx>]

From: Wei Chen <wei.chen@xxxxxxx>

The previous L3 page table size is a fixed value based on the
assumption that, image size will not exceed 2MB. But that's not
true, some applications like node.js will be about 40MB after
converting to Unikernel. So in this patch, we calculate the
page table size by real image size. In order to mapping the
image occupied memory to L3 page table, we round up the image
size with 2MB. If we don't round up the image size with 2MB.
Some memory that is not occupied by image but shared the same
2MB block with image tail will be unmapped in page table.

Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Signed-off-by: Jia He <justin.he@xxxxxxx>
---
v3->v4: fix IMAGE_ROUNDUP_SHIFT from 20 to 21

 plat/common/include/sections.h      | 31 +++++++++++++++++++++++++
 plat/kvm/arm/entry64.S              | 35 +++++++++++++++++++++++++++--
 plat/kvm/arm/pagetable64.S          |  4 +++-
 plat/kvm/arm/setup.c                |  2 +-
 plat/kvm/include/kvm-arm/arm64/mm.h | 14 +++++++-----
 5 files changed, 76 insertions(+), 10 deletions(-)

diff --git a/plat/common/include/sections.h b/plat/common/include/sections.h
index 42f41d2..f378093 100644
--- a/plat/common/include/sections.h
+++ b/plat/common/include/sections.h
@@ -35,6 +35,7 @@
 #ifndef __PLAT_CMN_SECTIONS_H__
 #define __PLAT_CMN_SECTIONS_H__
 
+#ifndef __ASSEMBLY__
 /*
  * Following global variables are defined in image link scripts, and some
  * variables are optional and may be unavailable on some architectures
@@ -62,4 +63,34 @@ extern char __bss_start[];
 /* _end: end of kernel image */
 extern char _end[];
 
+#endif /*__ASSEMBLY__*/
+
+/*
+ * Because the section is 4KB alignment, and we will assign different
+ * attributes for different sections. We roundup image size to 2MB to
+ * avoid making holes in L3 table
+ *
+ * L2 table
+ * |-----------|    L3 table
+ * |   2MB     |===>|-----------|
+ * |-----------|    |  4KB      | entry#0
+ *                  |-----------|
+ *                  |  ...      |
+ *                  |           |
+ *                  |-----------|
+ *                  |  4KB      | entry# for last page of real image
+ *                  |-----------|
+ *                  |  4KB      | entry# for round up memory
+ *                  |-----------|
+ *                  |  ...      |
+ *                  |-----------|
+ *                  |  4KB      | entry#511
+ *                  |-----------|
+ * If we don't roundup the image size to 2MB, some memory that is not
+ * occupied by image but shared the same 2MB block with image tail will
+ * not be mapped in page table.
+ */
+#define        IMAGE_ROUNDUP_SHIFT 21
+#define        IMAGE_ROUNDUP_SIZE (0x1 << (IMAGE_ROUNDUP_SHIFT))
+
 #endif /* __PLAT_CMN_SECTIONS_H__ */
diff --git a/plat/kvm/arm/entry64.S b/plat/kvm/arm/entry64.S
index d08b49e..12201a9 100644
--- a/plat/kvm/arm/entry64.S
+++ b/plat/kvm/arm/entry64.S
@@ -35,6 +35,12 @@
 #include <uk/asm.h>
 #include <kvm-arm/mm.h>
 #include <arm/cpu_defs.h>
+#include <sections.h>
+
+.global page_table_size
+.data
+page_table_size:
+       .dword 0x0
 
 /*
  * The registers used by _libkvmplat_start:
@@ -43,6 +49,28 @@
 
 .text
 ENTRY(_libkvmplat_entry)
+       /* Calculate the image size */
+       ldr x25, =_dtb
+       ldr x26, =_end
+       mov x15, x25
+       sub x15, x26, x15
+
+       /* Round up the size to 2MB */
+       mov x17, #(IMAGE_ROUNDUP_SIZE - 1)
+       add x15, x15, x17
+       lsr x15, x15, #IMAGE_ROUNDUP_SHIFT
+       lsl x15, x15, #IMAGE_ROUNDUP_SHIFT
+
+       /*
+        * How many bytes would be used for L3_TABLE
+        * ((x15 >> 21) << 12)
+        */
+       lsr x17, x15, #9
+
+       /* Total bytes for pagetable */
+       add x17, x17, #L0_TABLE_SIZE
+       add x17, x17, #L1_TABLE_SIZE
+       add x17, x17, #L2_TABLE_SIZE
 
        /*
         * Clean the boot stack and page table. As _end, PAGE_TABLE_SIZE and
@@ -50,8 +78,7 @@ ENTRY(_libkvmplat_entry)
         * 64-bytes alignment too. Execute 4 stp consecutively without boundary
         * check would be safe here.
         */
-       ldr x26, =_end
-       add x27, x26, #PAGE_TABLE_SIZE
+       add x27, x26, x17
        add x27, x27, #__STACK_SIZE
 1:
        stp xzr, xzr, [x26], #16
@@ -79,6 +106,10 @@ ENTRY(_libkvmplat_entry)
        /* Set the context id */
        msr contextidr_el1, xzr
 
+       /* Save page table size for later usage */
+       ldr x26, =page_table_size
+       str x17, [x26]
+
        /* Create a pagetable to do PA == VA mapping */
        bl create_pagetables
 
diff --git a/plat/kvm/arm/pagetable64.S b/plat/kvm/arm/pagetable64.S
index a00b71c..bd473bf 100644
--- a/plat/kvm/arm/pagetable64.S
+++ b/plat/kvm/arm/pagetable64.S
@@ -233,7 +233,9 @@ ENTRY(start_mmu)
         */
        ldr x0, =_data
        ldr x1, =_end
-       add x1, x1, #PAGE_TABLE_SIZE
+       ldr x2, =page_table_size
+       ldr x2, [x2]
+       add x1, x2, x1
        add x1, x1, #__STACK_SIZE
        sub x1, x1, x0
        bl clean_and_invalidate_dcache_range
diff --git a/plat/kvm/arm/setup.c b/plat/kvm/arm/setup.c
index 9c332ee..f98822c 100644
--- a/plat/kvm/arm/setup.c
+++ b/plat/kvm/arm/setup.c
@@ -146,7 +146,7 @@ static void _init_dtb_mem(void)
 
        max_addr = mem_base + mem_size;
        _libkvmplat_pagetable = (void *) ALIGN_DOWN((size_t)__END, __PAGE_SIZE);
-       _libkvmplat_heap_start = _libkvmplat_pagetable + PAGE_TABLE_SIZE;
+       _libkvmplat_heap_start = _libkvmplat_pagetable + page_table_size;
        _libkvmplat_mem_end = (void *) max_addr;
 
        /* AArch64 require stack be 16-bytes alignment by default */
diff --git a/plat/kvm/include/kvm-arm/arm64/mm.h 
b/plat/kvm/include/kvm-arm/arm64/mm.h
index 23bc658..9ec1273 100644
--- a/plat/kvm/include/kvm-arm/arm64/mm.h
+++ b/plat/kvm/include/kvm-arm/arm64/mm.h
@@ -69,15 +69,17 @@
 #define L2_TABLE_SIZE   __PAGE_SIZE
 
 /*
- * As Unikraft image's size is very tiny, from tens to hundreds kilo
- * bytes. So one page for L3_TABLE is enough for us to manage section
- * attributes of image.
+ * We will use Unikraft image's size to caculate the L3_TABLE_SIZE.
+ * Because we allocate one page for L2 TABLE, fo the max image size
+ * would be 1GB. It would be enough for current stage.
  */
 #define L3_TABLE_OFFSET (L2_TABLE_OFFSET + L2_TABLE_SIZE)
-#define L3_TABLE_SIZE   __PAGE_SIZE
+
+#ifndef __ASSEMBLY__
 
 /* Total memory size that will be used by pagetable */
-#define PAGE_TABLE_SIZE (L0_TABLE_SIZE + L1_TABLE_SIZE + \
-                               L2_TABLE_SIZE + L3_TABLE_SIZE)
+extern uint64_t page_table_size;
+
+#endif /*__ASSEMBLY__ */
 
 #endif /* __KVM_ARM_64_MM_H__ */
-- 
2.17.1


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