mm: Introduce per-arch pte_attr_t type for PTE flags

Oleksii Kurochko Tue, 11 Mar 2025 10:20:14 -0700


On 3/6/25 7:25 PM, Shawn Anastasio wrote:

Xen's memory management APIs map_pages_to_xen, modify_xen_mappings,
set_fixmap, ioremap_attr, and __vmap all use an unsigned int to
represent architecture-dependent page table entry flags. This assumption
is not well-suited for PPC/radix where some flags go past 32-bits, so
introduce the pte_attr_t type to allow architectures to opt in to larger
types to store PTE flags.


Suggested-by: Andrew Cooper<andrew.coop...@citrix.com>
Signed-off-by: Shawn Anastasio<sanasta...@raptorengineering.com>
---
Changes in v4:
   - Change definitions of map_pages_to_xen, modify_xen_mappings in all arches
   to match new prototype.
   - Use new flag types in modify_xen_mappings_lite as well (previously missed)

Changes in v3:
   - Use new asm/mm-types.h to pull in pte_attr_t definition when
   necessary.
   - Drop define+ifdef since pte_attr_t is now always defined.

Changes in v2:
   - Drop Kconfig option and use `#define pte_attr_t pte_attr_t` for arches to
   opt-in to defining the type.
   - Move default pte_attr_definition to xen/types.h
   - Update commit message to reflect that this change isn't strictly
   necessary for arches w/ >32bit pte flags

  xen/arch/arm/mmu/pt.c               | 4 ++--
  xen/arch/ppc/include/asm/Makefile   | 1 -
  xen/arch/ppc/include/asm/mm-types.h | 7 +++++++
  xen/arch/ppc/mm-radix.c             | 2 +-
  xen/arch/riscv/pt.c                 | 2 +-


Reviewed-by: Oleksii Kurochko<oleksii.kuroc...@gmail.com>

~ Oleksii

  xen/arch/x86/mm.c                   | 6 +++---
  xen/common/efi/boot.c               | 5 +++--
  xen/common/vmap.c                   | 2 +-
  xen/include/asm-generic/mm-types.h  | 2 ++
  xen/include/xen/mm.h                | 7 ++++---
  xen/include/xen/vmap.h              | 4 +++-
  11 files changed, 27 insertions(+), 15 deletions(-)
  create mode 100644 xen/arch/ppc/include/asm/mm-types.h

diff --git a/xen/arch/arm/mmu/pt.c b/xen/arch/arm/mmu/pt.c
index da28d669e7..9dc99db352 100644
--- a/xen/arch/arm/mmu/pt.c
+++ b/xen/arch/arm/mmu/pt.c
@@ -701,7 +701,7 @@ static int xen_pt_update(unsigned long virt,
  int map_pages_to_xen(unsigned long virt,
                       mfn_t mfn,
                       unsigned long nr_mfns,
-                     unsigned int flags)
+                     pte_attr_t flags)
  {
      return xen_pt_update(virt, mfn, nr_mfns, flags);
  }
@@ -719,7 +719,7 @@ int destroy_xen_mappings(unsigned long s, unsigned long e)
      return xen_pt_update(s, INVALID_MFN, (e - s) >> PAGE_SHIFT, 0);
  }

-int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
+int modify_xen_mappings(unsigned long s, unsigned long e, pte_attr_t nf)
  {
      ASSERT(IS_ALIGNED(s, PAGE_SIZE));
      ASSERT(IS_ALIGNED(e, PAGE_SIZE));
diff --git a/xen/arch/ppc/include/asm/Makefile 
b/xen/arch/ppc/include/asm/Makefile
index c0dbc68ac6..c989a7f89b 100644
--- a/xen/arch/ppc/include/asm/Makefile
+++ b/xen/arch/ppc/include/asm/Makefile
@@ -5,7 +5,6 @@ generic-y += div64.h
  generic-y += hardirq.h
  generic-y += hypercall.h
  generic-y += iocap.h
-generic-y += mm-types.h
  generic-y += paging.h
  generic-y += percpu.h
  generic-y += perfc_defn.h
diff --git a/xen/arch/ppc/include/asm/mm-types.h 
b/xen/arch/ppc/include/asm/mm-types.h
new file mode 100644
index 0000000000..0cb850f4f6
--- /dev/null
+++ b/xen/arch/ppc/include/asm/mm-types.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_PPC_MM_TYPES_H__
+#define __ASM_PPC_MM_TYPES_H__
+
+typedef unsigned long pte_attr_t;
+
+#endif /* __ASM_PPC_MM_TYPES_H__ */
diff --git a/xen/arch/ppc/mm-radix.c b/xen/arch/ppc/mm-radix.c
index 24232f3907..e02dffa7c5 100644
--- a/xen/arch/ppc/mm-radix.c
+++ b/xen/arch/ppc/mm-radix.c
@@ -265,7 +265,7 @@ int destroy_xen_mappings(unsigned long s, unsigned long e)
  int map_pages_to_xen(unsigned long virt,
                       mfn_t mfn,
                       unsigned long nr_mfns,
-                     unsigned int flags)
+                     pte_attr_t flags)
  {
      BUG_ON("unimplemented");
  }
diff --git a/xen/arch/riscv/pt.c b/xen/arch/riscv/pt.c
index 857619d48d..918b1b91ab 100644
--- a/xen/arch/riscv/pt.c
+++ b/xen/arch/riscv/pt.c
@@ -504,7 +504,7 @@ static int pt_update(vaddr_t virt, mfn_t mfn,
  int map_pages_to_xen(unsigned long virt,
                       mfn_t mfn,
                       unsigned long nr_mfns,
-                     unsigned int flags)
+                     pte_attr_t flags)
  {
      /*
       * Ensure that flags has PTE_VALID bit as map_pages_to_xen() is supposed
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index bfdc8fb019..53c17c6f88 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5472,7 +5472,7 @@ int map_pages_to_xen(
      unsigned long virt,
      mfn_t mfn,
      unsigned long nr_mfns,
-    unsigned int flags)
+    pte_attr_t flags)
  {
      bool locking = system_state > SYS_STATE_boot;
      l3_pgentry_t *pl3e = NULL, ol3e;
@@ -5890,7 +5890,7 @@ int __init populate_pt_range(unsigned long virt, unsigned 
long nr_mfns)
   *
   * It is an error to call with present flags over an unpopulated range.
   */
-int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
+int modify_xen_mappings(unsigned long s, unsigned long e, pte_attr_t nf)
  {
      bool locking = system_state > SYS_STATE_boot;
      l3_pgentry_t *pl3e = NULL;
@@ -6186,7 +6186,7 @@ int destroy_xen_mappings(unsigned long s, unsigned long e)
   * the non-inclusive boundary will be updated.
   */
  void init_or_livepatch modify_xen_mappings_lite(
-    unsigned long s, unsigned long e, unsigned int nf)
+    unsigned long s, unsigned long e, pte_attr_t nf)
  {
      unsigned long v = s, fm, flags;

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index efbec00af9..999dbce4dc 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1,4 +1,5 @@
  #include "efi.h"
+#include <asm/mm-types.h>
  #include <efi/efiprot.h>
  #include <efi/efipciio.h>
  #include <public/xen.h>
@@ -1656,7 +1657,7 @@ void __init efi_init_memory(void)
      struct rt_extra {
          struct rt_extra *next;
          unsigned long smfn, emfn;
-        unsigned int prot;
+        pte_attr_t prot;
      } *extra, *extra_head = NULL;

      free_ebmalloc_unused_mem();
@@ -1671,7 +1672,7 @@ void __init efi_init_memory(void)
          EFI_MEMORY_DESCRIPTOR *desc = efi_memmap + i;
          u64 len = desc->NumberOfPages << EFI_PAGE_SHIFT;
          unsigned long smfn, emfn;
-        unsigned int prot = PAGE_HYPERVISOR_RWX;
+        pte_attr_t prot = PAGE_HYPERVISOR_RWX;
          paddr_t mem_base;
          unsigned long mem_npages;

diff --git a/xen/common/vmap.c b/xen/common/vmap.c
index 47225fecc0..d6991421f3 100644
--- a/xen/common/vmap.c
+++ b/xen/common/vmap.c
@@ -222,7 +222,7 @@ static void vm_free(const void *va)
  }

  void *__vmap(const mfn_t *mfn, unsigned int granularity,
-             unsigned int nr, unsigned int align, unsigned int flags,
+             unsigned int nr, unsigned int align, pte_attr_t flags,
               enum vmap_region type)
  {
      void *va = vm_alloc(nr * granularity, align, type);
diff --git a/xen/include/asm-generic/mm-types.h 
b/xen/include/asm-generic/mm-types.h
index 26490e48db..9eb3cba698 100644
--- a/xen/include/asm-generic/mm-types.h
+++ b/xen/include/asm-generic/mm-types.h
@@ -2,4 +2,6 @@
  #ifndef __ASM_GENERIC_MM_TYPES_H__
  #define __ASM_GENERIC_MM_TYPES_H__

+typedef unsigned int pte_attr_t;
+
  #endif /* __ASM_GENERIC_MM_TYPES_H__ */
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 16f733281a..e79f1728c3 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -69,6 +69,7 @@
  #include <xen/spinlock.h>
  #include <xen/perfc.h>
  #include <public/memory.h>
+#include <asm/mm-types.h>

  struct page_info;

@@ -113,11 +114,11 @@ int map_pages_to_xen(
      unsigned long virt,
      mfn_t mfn,
      unsigned long nr_mfns,
-    unsigned int flags);
+    pte_attr_t flags);
  /* Alter the permissions of a range of Xen virtual address space. */
-int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf);
+int modify_xen_mappings(unsigned long s, unsigned long e, pte_attr_t nf);
  void modify_xen_mappings_lite(unsigned long s, unsigned long e,
-                              unsigned int nf);
+                              pte_attr_t nf);
  int destroy_xen_mappings(unsigned long s, unsigned long e);
  /* Retrieve the MFN mapped by VA in Xen virtual address space. */
  mfn_t xen_map_to_mfn(unsigned long va);
diff --git a/xen/include/xen/vmap.h b/xen/include/xen/vmap.h
index 26c831757a..e1155ed14a 100644
--- a/xen/include/xen/vmap.h
+++ b/xen/include/xen/vmap.h
@@ -8,8 +8,10 @@
  #ifndef __XEN_VMAP_H__
  #define __XEN_VMAP_H__

+#include <xen/mm.h>
  #include <xen/mm-frame.h>
  #include <xen/page-size.h>
+#include <asm/mm-types.h>

  /* Identifiers for the linear ranges tracked by vmap */
  enum vmap_region {
@@ -57,7 +59,7 @@ void vm_init_type(enum vmap_region type, void *start, void 
*end);
   * @return Pointer to the mapped area on success; NULL otherwise.
   */
  void *__vmap(const mfn_t *mfn, unsigned int granularity, unsigned int nr,
-             unsigned int align, unsigned int flags, enum vmap_region type);
+             unsigned int align, pte_attr_t flags, enum vmap_region type);

  /*
   * Map an array of pages contiguously into the VMAP_DEFAULT vmap region
--
2.30.2

Re: [PATCH v4 2/2] xen/mm: Introduce per-arch pte_attr_t type for PTE flags

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