[PATCH v2 4/8] xen/riscv: setup fixmap mapping

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Introduce a function to set up fixmap mappings and L0 page
table for fixmap.

Additionally, defines were introduced in riscv/config.h to
calculate the FIXMAP_BASE address.
This involved introducing BOOT_FDT_VIRT_{START, SIZE} and
XEN_SIZE, XEN_VIRT_END.

Also, the check of Xen size was updated in the riscv/lds.S
script to use XEN_SIZE instead of a hardcoded constant.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V2:
 - newly introduced patch
---
 xen/arch/riscv/include/asm/config.h |  9 ++++++
 xen/arch/riscv/include/asm/fixmap.h | 48 +++++++++++++++++++++++++++++
 xen/arch/riscv/include/asm/mm.h     |  2 ++
 xen/arch/riscv/include/asm/page.h   |  7 +++++
 xen/arch/riscv/mm.c                 | 35 +++++++++++++++++++++
 xen/arch/riscv/setup.c              |  2 ++
 xen/arch/riscv/xen.lds.S            |  2 +-
 7 files changed, 104 insertions(+), 1 deletion(-)
 create mode 100644 xen/arch/riscv/include/asm/fixmap.h

diff --git a/xen/arch/riscv/include/asm/config.h 
b/xen/arch/riscv/include/asm/config.h
index 50583aafdc..3275477c17 100644
--- a/xen/arch/riscv/include/asm/config.h
+++ b/xen/arch/riscv/include/asm/config.h
@@ -74,11 +74,20 @@
 #error "unsupported RV_STAGE1_MODE"
 #endif
 
+#define XEN_SIZE                MB(2)
+#define XEN_VIRT_END            (XEN_VIRT_START + XEN_SIZE)
+
+#define BOOT_FDT_VIRT_START     XEN_VIRT_END
+#define BOOT_FDT_VIRT_SIZE      MB(4)
+
 #define DIRECTMAP_SLOT_END      509
 #define DIRECTMAP_SLOT_START    200
 #define DIRECTMAP_VIRT_START    SLOTN(DIRECTMAP_SLOT_START)
 #define DIRECTMAP_SIZE          (SLOTN(DIRECTMAP_SLOT_END) - 
SLOTN(DIRECTMAP_SLOT_START))
 
+#define FIXMAP_BASE             (BOOT_FDT_VIRT_START + BOOT_FDT_VIRT_SIZE)
+#define FIXMAP_ADDR(n)          (FIXMAP_BASE + (n) * PAGE_SIZE)
+
 #define FRAMETABLE_SCALE_FACTOR  (PAGE_SIZE/sizeof(struct page_info))
 #define FRAMETABLE_SIZE_IN_SLOTS (((DIRECTMAP_SIZE / SLOTN(1)) / 
FRAMETABLE_SCALE_FACTOR) + 1)
 
diff --git a/xen/arch/riscv/include/asm/fixmap.h 
b/xen/arch/riscv/include/asm/fixmap.h
new file mode 100644
index 0000000000..fcfb82d69c
--- /dev/null
+++ b/xen/arch/riscv/include/asm/fixmap.h
@@ -0,0 +1,48 @@
+/*
+ * fixmap.h: compile-time virtual memory allocation
+ */
+#ifndef __ASM_FIXMAP_H
+#define __ASM_FIXMAP_H
+
+#include <xen/bug.h>
+#include <xen/page-size.h>
+#include <xen/pmap.h>
+
+#include <asm/page.h>
+
+/* Fixmap slots */
+#define FIX_PMAP_BEGIN (0) /* Start of PMAP */
+#define FIX_PMAP_END (FIX_PMAP_BEGIN + NUM_FIX_PMAP - 1) /* End of PMAP */
+#define FIX_MISC (FIX_PMAP_END + 1)  /* Ephemeral mappings of hardware */
+
+#define FIX_LAST FIX_MISC
+
+#define FIXADDR_START FIXMAP_ADDR(0)
+#define FIXADDR_TOP FIXMAP_ADDR(FIX_LAST)
+
+#ifndef __ASSEMBLY__
+
+/*
+ * Direct access to xen_fixmap[] should only happen when {set,
+ * clear}_fixmap() is unusable (e.g. where we would end up to
+ * recursively call the helpers).
+ */
+extern pte_t xen_fixmap[];
+
+/* Map a page in a fixmap entry */
+extern void set_fixmap(unsigned int map, mfn_t mfn, unsigned int attributes);
+/* Remove a mapping from a fixmap entry */
+extern void clear_fixmap(unsigned int map);
+
+#define fix_to_virt(slot) ((void *)FIXMAP_ADDR(slot))
+
+static inline unsigned int virt_to_fix(vaddr_t vaddr)
+{
+    BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
+
+    return ((vaddr - FIXADDR_START) >> PAGE_SHIFT);
+}
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_FIXMAP_H */
diff --git a/xen/arch/riscv/include/asm/mm.h b/xen/arch/riscv/include/asm/mm.h
index 25af9e1aaa..a0bdc2bc3a 100644
--- a/xen/arch/riscv/include/asm/mm.h
+++ b/xen/arch/riscv/include/asm/mm.h
@@ -255,4 +255,6 @@ static inline unsigned int arch_get_dma_bitsize(void)
     return 32; /* TODO */
 }
 
+void setup_fixmap_mappings(void);
+
 #endif /* _ASM_RISCV_MM_H */
diff --git a/xen/arch/riscv/include/asm/page.h 
b/xen/arch/riscv/include/asm/page.h
index c831e16417..cbbf3656d1 100644
--- a/xen/arch/riscv/include/asm/page.h
+++ b/xen/arch/riscv/include/asm/page.h
@@ -81,6 +81,13 @@ static inline void flush_page_to_ram(unsigned long mfn, bool 
sync_icache)
     BUG_ON("unimplemented");
 }
 
+/* Write a pagetable entry. */
+static inline void write_pte(pte_t *p, pte_t pte)
+{
+    *p = pte;
+    asm volatile ("sfence.vma");
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_RISCV_PAGE_H */
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index 7d09e781bf..d69a174b5d 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -49,6 +49,9 @@ stage1_pgtbl_root[PAGETABLE_ENTRIES];
 pte_t __section(".bss.page_aligned") __aligned(PAGE_SIZE)
 stage1_pgtbl_nonroot[PGTBL_INITIAL_COUNT * PAGETABLE_ENTRIES];
 
+pte_t __section(".bss.page_aligned") __aligned(PAGE_SIZE)
+xen_fixmap[PAGETABLE_ENTRIES];
+
 #define HANDLE_PGTBL(curr_lvl_num)                                          \
     index = pt_index(curr_lvl_num, page_addr);                              \
     if ( pte_is_valid(pgtbl[index]) )                                       \
@@ -191,6 +194,38 @@ static bool __init check_pgtbl_mode_support(struct 
mmu_desc *mmu_desc,
     return is_mode_supported;
 }
 
+void __init setup_fixmap_mappings(void)
+{
+    pte_t *pte;
+    unsigned int i;
+
+    pte = &stage1_pgtbl_root[pt_index(HYP_PT_ROOT_LEVEL, FIXMAP_ADDR(0))];
+
+    for ( i = HYP_PT_ROOT_LEVEL - 1; i != 0; i-- )
+    {
+        BUG_ON(!pte_is_valid(*pte));
+
+        pte = (pte_t *)LOAD_TO_LINK(pte_to_paddr(*pte));
+        pte = &pte[pt_index(i, FIXMAP_ADDR(0))];
+    }
+
+    BUG_ON( pte_is_valid(*pte) );
+
+    if ( !pte_is_valid(*pte) )
+    {
+        pte_t tmp = paddr_to_pte(LINK_TO_LOAD((unsigned long)&xen_fixmap), 
PTE_TABLE);
+
+        write_pte(pte, tmp);
+
+        printk("(XEN) fixmap is mapped\n");
+    }
+
+    /*
+     * We only need the zeroeth table allocated, but not the PTEs set, because
+     * set_fixmap() will set them on the fly.
+     */
+}
+
 /*
  * setup_initial_pagetables:
  *
diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
index 4defad68f4..13f0e8c77d 100644
--- a/xen/arch/riscv/setup.c
+++ b/xen/arch/riscv/setup.c
@@ -46,6 +46,8 @@ void __init noreturn start_xen(unsigned long bootcpu_id,
     test_macros_from_bug_h();
 #endif
 
+    setup_fixmap_mappings();
+
     printk("All set up\n");
 
     for ( ;; )
diff --git a/xen/arch/riscv/xen.lds.S b/xen/arch/riscv/xen.lds.S
index 070b19d915..63b1dd7bb6 100644
--- a/xen/arch/riscv/xen.lds.S
+++ b/xen/arch/riscv/xen.lds.S
@@ -181,6 +181,6 @@ ASSERT(!SIZEOF(.got.plt),  ".got.plt non-empty")
  * Changing the size of Xen binary can require an update of
  * PGTBL_INITIAL_COUNT.
  */
-ASSERT(_end - _start <= MB(2), "Xen too large for early-boot assumptions")
+ASSERT(_end - _start <= XEN_SIZE, "Xen too large for early-boot assumptions")
 
 ASSERT(_ident_end - _ident_start <= IDENT_AREA_SIZE, "identity region is too 
big");
-- 
2.45.2