[PATCH 2/5] xen/riscv: preset A/D bits in Xen's own page-table mappings

[Baptiste Le Duc <baptiste.le-duc@xxxxxxxxxx>]

The previous patch made p2m_set_permission() always set the PTE A/D bits to
map pages in G-stage, to avoid a page fault on platforms that implement
neither Svade nor Svadu, or that declare both in the device tree. Xen's own
page tables, built by setup_initial_mapping(), never go through
p2m_set_permission() and need the same fix.

Add PTE_ACCESSED to PTE_LEAF_DEFAULT and make it the minimal common leaf
permission set by dropping PTE_WRITABLE. Rebuild PAGE_HYPERVISOR_RO,
PAGE_HYPERVISOR_RW and PAGE_HYPERVISOR_RX from that common base, with
PAGE_HYPERVISOR_RW also adding PTE_DIRTY. Switch setup_initial_mapping() to
use these macros for its default, text, and rodata permissions instead of
the equivalent raw bit lists.

A PTE is a table entry iff PTE_VALID is set and R/W/X are all clear, so
update pte_is_table() accordingly.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Baptiste Le Duc <baptiste.le-duc@xxxxxxxxxx>
---
 xen/arch/riscv/include/asm/page.h | 14 ++++++++------
 xen/arch/riscv/mm.c               |  7 +++----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/xen/arch/riscv/include/asm/page.h 
b/xen/arch/riscv/include/asm/page.h
index b465a90325..5c02f64a17 100644
--- a/xen/arch/riscv/include/asm/page.h
+++ b/xen/arch/riscv/include/asm/page.h
@@ -46,12 +46,12 @@
 #define PTE_PBMT_NOCACHE            BIT(61, UL)
 #define PTE_PBMT_IO                 BIT(62, UL)
 
-#define PTE_LEAF_DEFAULT            (PTE_VALID | PTE_READABLE | PTE_WRITABLE)
+#define PTE_LEAF_DEFAULT            (PTE_VALID | PTE_READABLE | PTE_ACCESSED)
 #define PTE_TABLE                   (PTE_VALID)
 
-#define PAGE_HYPERVISOR_RO          (PTE_VALID | PTE_READABLE)
-#define PAGE_HYPERVISOR_RW          (PTE_VALID | PTE_READABLE | PTE_WRITABLE)
-#define PAGE_HYPERVISOR_RX          (PTE_VALID | PTE_READABLE | PTE_EXECUTABLE)
+#define PAGE_HYPERVISOR_RO          (PTE_LEAF_DEFAULT)
+#define PAGE_HYPERVISOR_RW          (PTE_LEAF_DEFAULT | PTE_WRITABLE | 
PTE_DIRTY)
+#define PAGE_HYPERVISOR_RX          (PTE_LEAF_DEFAULT | PTE_EXECUTABLE)
 
 #define PAGE_HYPERVISOR             PAGE_HYPERVISOR_RW
 /*
@@ -177,7 +177,8 @@ static inline bool pte_is_table(pte_t p)
      *
      * PAGE_HYPERVISOR_RW contains PTE_VALID too.
      */
-    ASSERT(((p.pte & PAGE_HYPERVISOR_RW) != (PTE_VALID | PTE_WRITABLE)));
+    ASSERT((p.pte & (PTE_VALID | PTE_READABLE | PTE_WRITABLE)) !=
+           (PTE_VALID | PTE_WRITABLE));
 
     return ((p.pte & (PTE_VALID | PTE_ACCESS_MASK)) == PTE_VALID);
 }
@@ -185,7 +186,8 @@ static inline bool pte_is_table(pte_t p)
 static inline bool pte_is_mapping(pte_t p)
 {
     /* See pte_is_table() */
-    ASSERT(((p.pte & PAGE_HYPERVISOR_RW) != (PTE_VALID | PTE_WRITABLE)));
+    ASSERT((p.pte & (PTE_VALID | PTE_READABLE | PTE_WRITABLE)) !=
+            (PTE_VALID | PTE_WRITABLE));
 
     return (p.pte & PTE_VALID) && (p.pte & PTE_ACCESS_MASK);
 }
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index 4d3b8c2204..baff49cf09 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -140,7 +140,7 @@ static void __init setup_initial_mapping(struct mmu_desc 
*mmu_desc,
         case 1: /* Level 0 */
             {
                 unsigned long paddr = (page_addr - map_start) + pa_start;
-                unsigned int permissions = PTE_LEAF_DEFAULT;
+                unsigned int permissions = PAGE_HYPERVISOR_RW;
                 unsigned long addr = is_identity_mapping
                                      ? page_addr : virt_to_maddr(page_addr);
                 pte_t pte_to_be_written;
@@ -149,11 +149,10 @@ static void __init setup_initial_mapping(struct mmu_desc 
*mmu_desc,
 
                 if ( is_kernel_text(addr) ||
                      is_kernel_inittext(addr) )
-                        permissions =
-                            PTE_EXECUTABLE | PTE_READABLE | PTE_VALID;
+                    permissions = PAGE_HYPERVISOR_RX;
 
                 if ( is_kernel_rodata(addr) )
-                    permissions = PTE_READABLE | PTE_VALID;
+                    permissions = PAGE_HYPERVISOR_RO;
 
                 pte_to_be_written = paddr_to_pte(paddr, permissions);