[PATCH v2] xen/riscv: Increase XEN_VIRT_SIZE

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

A randconfig job failed with the following issue:
  riscv64-linux-gnu-ld: Xen too large for early-boot assumptions

The reason is that enabling the UBSAN config increased the size of
the Xen binary.

Increase XEN_VIRT_SIZE to reserve enough space, allowing both UBSAN
and GCOV to be enabled together, with some slack for future growth.

Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in v2:
 - Incerease XEN_VIRT_SIZE to 16 Mb to cover also the case if 2M mappings will
   be used for .text (rx), .rodata(r), and .data (rw).
 - Update layout table in config.h.
 - s/xen_virt_starn_vpn/xen_virt_start_vpn
 - Update BUILD_BUG_ON(... != MB(8)) check to "... > GB(1)".
 - Update definition of PGTBL_INITIAL_COUNT and the comment above.
---
 xen/arch/riscv/include/asm/config.h |  8 ++++----
 xen/arch/riscv/include/asm/mm.h     | 12 +++++++++---
 xen/arch/riscv/mm.c                 | 25 ++++++++++++++++---------
 3 files changed, 29 insertions(+), 16 deletions(-)

diff --git a/xen/arch/riscv/include/asm/config.h 
b/xen/arch/riscv/include/asm/config.h
index 7141bd9e46..41b8410d10 100644
--- a/xen/arch/riscv/include/asm/config.h
+++ b/xen/arch/riscv/include/asm/config.h
@@ -41,11 +41,11 @@
  * Start addr          | End addr         | Slot       | area description
  * ============================================================================
  *                   .....                 L2 511          Unused
- *  0xffffffffc0a00000  0xffffffffc0bfffff L2 511          Fixmap
+ *  0xffffffffc1800000  0xffffffffc1afffff L2 511          Fixmap
  *                   ..... ( 2 MB gap )
- *  0xffffffffc0400000  0xffffffffc07fffff L2 511          FDT
+ *  0xffffffffc1200000  0xffffffffc15fffff L2 511          FDT
  *                   ..... ( 2 MB gap )
- *  0xffffffffc0000000  0xffffffffc01fffff L2 511          Xen
+ *  0xffffffffc0000000  0xffffffffc0ffffff L2 511          Xen
  *                   .....                 L2 510          Unused
  *  0x3200000000        0x7f7fffffff       L2 200-509      Direct map
  *                   .....                 L2 199          Unused
@@ -78,7 +78,7 @@
 
 #define GAP_SIZE                MB(2)
 
-#define XEN_VIRT_SIZE           MB(2)
+#define XEN_VIRT_SIZE           MB(16)
 
 #define BOOT_FDT_VIRT_START     (XEN_VIRT_START + XEN_VIRT_SIZE + GAP_SIZE)
 #define BOOT_FDT_VIRT_SIZE      MB(4)
diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index 4035cd400a..511e75c6d4 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -43,13 +43,19 @@ static inline void *maddr_to_virt(paddr_t ma)
  */
 static inline unsigned long virt_to_maddr(unsigned long va)
 {
+    const unsigned int vpn1_shift = PAGETABLE_ORDER + PAGE_SHIFT;
+    const unsigned long va_vpn = va >> vpn1_shift;
+    const unsigned long xen_virt_start_vpn =
+        _AC(XEN_VIRT_START, UL) >> vpn1_shift;
+    const unsigned long xen_virt_end_vpn =
+        xen_virt_start_vpn + ((XEN_VIRT_SIZE >> vpn1_shift) - 1);
+
     if ((va >= DIRECTMAP_VIRT_START) &&
         (va <= DIRECTMAP_VIRT_END))
         return directmapoff_to_maddr(va - directmap_virt_start);
 
-    BUILD_BUG_ON(XEN_VIRT_SIZE != MB(2));
-    ASSERT((va >> (PAGETABLE_ORDER + PAGE_SHIFT)) ==
-           (_AC(XEN_VIRT_START, UL) >> (PAGETABLE_ORDER + PAGE_SHIFT)));
+    BUILD_BUG_ON(XEN_VIRT_SIZE > GB(1));
+    ASSERT((va_vpn >= xen_virt_start_vpn) && (va_vpn <= xen_virt_end_vpn));
 
     /* phys_offset = load_start - XEN_VIRT_START */
     return phys_offset + va;
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index f2bf279bac..256afdaaa3 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -31,20 +31,27 @@ unsigned long __ro_after_init phys_offset; /* = load_start 
- XEN_VIRT_START */
 #define LOAD_TO_LINK(addr) ((unsigned long)(addr) - phys_offset)
 
 /*
- * It is expected that Xen won't be more then 2 MB.
+ * It is expected that Xen won't be more then XEN_VIRT_SIZE MB.
  * The check in xen.lds.S guarantees that.
- * At least 3 page tables (in case of Sv39 ) are needed to cover 2 MB.
- * One for each page level table with PAGE_SIZE = 4 Kb.
  *
- * One L0 page table can cover 2 MB(512 entries of one page table * PAGE_SIZE).
+ * Root page table is shared with the initial mapping and is declared
+ * separetely. (look at stage1_pgtbl_root)
  *
- * It might be needed one more page table in case when Xen load address
- * isn't 2 MB aligned.
+ * An amount of page tables between root page table and L0 page table
+ * (in the case of Sv39 it covers L1 table):
+ *   (CONFIG_PAGING_LEVELS - 2) are needed for an identity mapping and
+ *   the same amount are needed for Xen.
  *
- * CONFIG_PAGING_LEVELS page tables are needed for the identity mapping,
- * except that the root page table is shared with the initial mapping
+ * An amount of L0 page tables:
+ *   (512 entries of one L0 page table covers 2MB == 1<<XEN_PT_LEVEL_SHIFT(1))
+ *   XEN_VIRT_SIZE >> XEN_PT_LEVEL_SHIFT(1) are needed for Xen and
+ *   one L0 is needed for indenity mapping.
+ *
+ *   It might be needed one more page table in case when Xen load
+ *   address isn't 2 MB aligned.
  */
-#define PGTBL_INITIAL_COUNT ((CONFIG_PAGING_LEVELS - 1) * 2 + 1)
+#define PGTBL_INITIAL_COUNT ((CONFIG_PAGING_LEVELS - 2) * 2 + \
+                             (XEN_VIRT_SIZE >> XEN_PT_LEVEL_SHIFT(1)) + 2)
 
 pte_t __section(".bss.page_aligned") __aligned(PAGE_SIZE)
 stage1_pgtbl_root[PAGETABLE_ENTRIES];
-- 
2.49.0