[Xen-devel] [PATCH v7 03/14] arm/mem_access: Add defines supporting PTs with varying page sizes

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

AArch64 supports pages with different (4K, 16K, and 64K) sizes.  To
enable guest page table walks for various configurations, this commit
extends the defines and helpers of the current implementation.

Signed-off-by: Sergej Proskurin <proskurin@xxxxxxxxxxxxx>
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
---
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
v3: Eliminate redundant macro definitions by introducing generic macros.

v4: Replace existing macros with ones that generate static inline
    helpers as to ease the readability of the code.

    Move the introduced code into lpae.h

v5: Remove PAGE_SHIFT_* defines from lpae.h as we import them now from
    the header xen/lib.h.

    Remove *_guest_table_offset macros as to reduce the number of
    exported macros which are only used once. Instead, use the
    associated functionality directly within the
    GUEST_TABLE_OFFSET_HELPERS.

    Add comment in GUEST_TABLE_OFFSET_HELPERS stating that a page table
    with 64K page size granularity does not have a zeroeth lookup level.

    Add #undefs for GUEST_TABLE_OFFSET and GUEST_TABLE_OFFSET_HELPERS.

    Remove CONFIG_ARM_64 #defines.

v6: Rename *_guest_table_offset_* helpers to *_table_offset_* as they
    are sufficiently generic to be applied not only to the guest's page
    table walks.

    Change the type of the parameter and return value of the
    *_table_offset_* helpers from vaddr_t to paddr_t to enable applying
    these helpers also for other purposes such as computation of IPA
    offsets in second stage translation tables.

v7: Clarify comments in the code and commit message to address AArch64
    directly instead of ARMv8 in general.

    Rename remaining GUEST_TABLE_* macros into TABLE_* macros, to be
    consistent with *_table_offset_* helpers.

    Added Reviewed-by Julien Grall.
---
 xen/include/asm-arm/lpae.h | 61 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/xen/include/asm-arm/lpae.h b/xen/include/asm-arm/lpae.h
index a62b118630..efec493313 100644
--- a/xen/include/asm-arm/lpae.h
+++ b/xen/include/asm-arm/lpae.h
@@ -3,6 +3,8 @@
 
 #ifndef __ASSEMBLY__
 
+#include <xen/page-defs.h>
+
 /*
  * WARNING!  Unlike the x86 pagetable code, where l1 is the lowest level and
  * l4 is the root of the trie, the ARM pagetables follow ARM's documentation:
@@ -151,6 +153,65 @@ static inline bool lpae_is_superpage(lpae_t pte, unsigned 
int level)
     return (level < 3) && lpae_mapping(pte);
 }
 
+/*
+ * AArch64 supports pages with different sizes (4K, 16K, and 64K). To enable
+ * page table walks for various configurations, the following helpers enable
+ * walking the translation table with varying page size granularities.
+ */
+
+#define LPAE_SHIFT_4K           (9)
+#define LPAE_SHIFT_16K          (11)
+#define LPAE_SHIFT_64K          (13)
+
+#define lpae_entries(gran)      (_AC(1,U) << LPAE_SHIFT_##gran)
+#define lpae_entry_mask(gran)   (lpae_entries(gran) - 1)
+
+#define third_shift(gran)       (PAGE_SHIFT_##gran)
+#define third_size(gran)        ((paddr_t)1 << third_shift(gran))
+
+#define second_shift(gran)      (third_shift(gran) + LPAE_SHIFT_##gran)
+#define second_size(gran)       ((paddr_t)1 << second_shift(gran))
+
+#define first_shift(gran)       (second_shift(gran) + LPAE_SHIFT_##gran)
+#define first_size(gran)        ((paddr_t)1 << first_shift(gran))
+
+/* Note that there is no zeroeth lookup level with a 64K granule size. */
+#define zeroeth_shift(gran)     (first_shift(gran) + LPAE_SHIFT_##gran)
+#define zeroeth_size(gran)      ((paddr_t)1 << zeroeth_shift(gran))
+
+#define TABLE_OFFSET(offs, gran)      (offs & lpae_entry_mask(gran))
+#define TABLE_OFFSET_HELPERS(gran)                                          \
+static inline paddr_t third_table_offset_##gran##K(paddr_t va)              \
+{                                                                           \
+    return TABLE_OFFSET((va >> third_shift(gran##K)), gran##K);             \
+}                                                                           \
+                                                                            \
+static inline paddr_t second_table_offset_##gran##K(paddr_t va)             \
+{                                                                           \
+    return TABLE_OFFSET((va >> second_shift(gran##K)), gran##K);            \
+}                                                                           \
+                                                                            \
+static inline paddr_t first_table_offset_##gran##K(paddr_t va)              \
+{                                                                           \
+    return TABLE_OFFSET((va >> first_shift(gran##K)), gran##K);             \
+}                                                                           \
+                                                                            \
+static inline paddr_t zeroeth_table_offset_##gran##K(paddr_t va)            \
+{                                                                           \
+    /* Note that there is no zeroeth lookup level with 64K granule sizes. */\
+    if ( gran == 64 )                                                       \
+        return 0;                                                           \
+    else                                                                    \
+        return TABLE_OFFSET((va >> zeroeth_shift(gran##K)), gran##K);       \
+}                                                                           \
+
+TABLE_OFFSET_HELPERS(4);
+TABLE_OFFSET_HELPERS(16);
+TABLE_OFFSET_HELPERS(64);
+
+#undef TABLE_OFFSET
+#undef TABLE_OFFSET_HELPERS
+
 #endif /* __ASSEMBLY__ */
 
 /*
-- 
2.13.2


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