xen/riscv: Increase XEN_VIRT_SIZE

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.

Additionally, add checks to verify that XEN_VIRT_START is 1GB-aligned
and XEN_VIRT_SIZE is 2MB-aligned to reduce the number of page tables
needed for the initial mapping. In the future, when 2MB mappings are
used for .text (rx), .rodata (r), and .data (rw), this will also help
reduce TLB pressure.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/riscv/include/asm/config.h b/xen/arch/riscv/include/asm/config.h
index 314c97c20aa5832308b5176679a0d4970f51b93b..e150f28f536da72708d582d56ad5876f5618de09 100644 (file)
--- 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  0xffffffffc19fffff 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 4035cd400a95bc222a1759a8aadbbe6cfb5abbf2..ef8b35d7c2d74ec252c770d82c5d852e8d76da8f 100644 (file)
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -9,6 +9,7 @@
 #include <xen/mm-frame.h>
 #include <xen/pdx.h>
 #include <xen/pfn.h>
+#include <xen/sections.h>
 #include <xen/types.h>
 
 #include <asm/page-bits.h>
@@ -43,13 +44,21 @@ static inline void *maddr_to_virt(paddr_t ma)
  */
 static inline unsigned long virt_to_maddr(unsigned long va)
 {
+    const unsigned long xen_size = (unsigned long)(_end - _start);
+    const unsigned long xen_virt_start = _AC(XEN_VIRT_START, UL);
+    const unsigned long xen_virt_end = xen_virt_start + xen_size - 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)));
+    ASSERT((va >= xen_virt_start) && (va <= xen_virt_end));
+
+    /*
+    * The .init* sections will be freed when Xen completes booting,
+    * so the [__init_begin, __init_end) range must be excluded.
+    */
+    ASSERT((system_state < SYS_STATE_active) || !is_init_section(va));
 
     /* 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 f2bf279bacfcbedd50e031aae4837d9a7401e4f9..d3ece9f132c119cc7decf464be8679156466eba9 100644 (file)
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -31,20 +31,39 @@ 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.
  * 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
+ * separately (look at stage1_pgtbl_root), so it isn't taken into account
+ * in PGTBL_INITIAL_COUNT.
  *
- * 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 identity mapping.
  */
-#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)) + 1)
+
+/*
+ * Modifying these checks may require updating PGTBL_INITIAL_COUNT.
+ *
+ * If XEN_VIRT_{START,SIZE} are not properly aligned and XEN_VIRT_SIZE > GB(1),
+ * additional L1 and L0 page tables are required.
+ */
+static void __init __maybe_unused build_assertions(void)
+{
+    BUILD_BUG_ON(!IS_ALIGNED(XEN_VIRT_START, GB(1)));
+    BUILD_BUG_ON(!IS_ALIGNED(XEN_VIRT_SIZE, MB(2)));
+
+    BUILD_BUG_ON(XEN_VIRT_SIZE > GB(1));
+}
 
 pte_t __section(".bss.page_aligned") __aligned(PAGE_SIZE)
 stage1_pgtbl_root[PAGETABLE_ENTRIES];

diff --git a/xen/include/xen/sections.h b/xen/include/xen/sections.h
index f2fac8d7fa29cf2f0d06c8a048a7490647af5cd3..fe49d7d0e63ab59ac53284446a01f51d8d306d28 100644 (file)
--- a/xen/include/xen/sections.h
+++ b/xen/include/xen/sections.h
@@ -7,6 +7,10 @@
 
 /* SAF-0-safe */
 extern char __init_begin[], __init_end[];
+#define is_init_section(p) ({                           \
+    const char *p_ = (const char *)(unsigned long)(p);  \
+    (p_ >= __init_begin) && (p_ < __init_end);          \
+})
 
 /*
  * Some data is expected to be written rarely (if at all).