[Xen-devel] [PATCH v7 05/16] xen: add function for obtaining highest possible memory address

[Juergen Gross <jgross@xxxxxxxx>]

Add a function for obtaining the highest possible physical memory
address of the system. This value is influenced by:

- hypervisor configuration (CONFIG_BIGMEM)
- processor capability (max. addressable physical memory)
- memory map at boot time
- memory hotplug capability

The value is especially needed for dom0 to decide sizing of grant frame
limits of guests and for pv domains for selecting the grant interface
version to use.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/mm.c        | 11 +++++++++++
 xen/common/memory.c      |  8 ++++++++
 xen/include/asm-arm/mm.h |  5 +++++
 xen/include/asm-x86/mm.h |  2 ++
 xen/include/xen/mm.h     |  3 +++
 5 files changed, 29 insertions(+)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 67f583e3a7..31d96a3920 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -6312,6 +6312,17 @@ int pv_ro_page_fault(unsigned long addr, struct 
cpu_user_regs *regs)
     return 0;
 }
 
+unsigned long arch_get_upper_mfn_bound(void)
+{
+    unsigned long max_mfn;
+
+    max_mfn = mem_hotplug ? PFN_DOWN(mem_hotplug) : max_page;
+#ifndef CONFIG_BIGMEM
+    max_mfn = min(max_mfn, 1UL << 32);
+#endif
+    return min(max_mfn, 1UL << (paddr_bits - PAGE_SHIFT));
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/common/memory.c b/xen/common/memory.c
index a2abf554e3..27e39cf45c 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -1494,6 +1494,14 @@ int prepare_ring_for_helper(
     return 0;
 }
 
+unsigned long get_upper_mfn_bound(void)
+{
+    unsigned long max_mfn;
+
+    max_mfn = arch_get_upper_mfn_bound();
+    return max(max_mfn, max_page);
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index cd6dfb54b9..6aa8cba5e0 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -376,6 +376,11 @@ static inline void put_page_and_type(struct page_info 
*page)
 
 void clear_and_clean_page(struct page_info *page);
 
+static inline unsigned long arch_get_upper_mfn_bound(void)
+{
+    return 0;
+}
+
 #endif /*  __ARCH_ARM_MM__ */
 /*
  * Local variables:
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index bef45e8e9f..91b62b111e 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -608,4 +608,6 @@ static inline bool arch_mfn_in_directmap(unsigned long mfn)
     return mfn <= (virt_to_mfn(eva - 1) + 1);
 }
 
+unsigned long arch_get_upper_mfn_bound(void);
+
 #endif /* __ASM_X86_MM_H__ */
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index f8b6177c32..e813c07b22 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -599,6 +599,9 @@ int prepare_ring_for_helper(struct domain *d, unsigned long 
gmfn,
                             struct page_info **_page, void **_va);
 void destroy_ring_for_helper(void **_va, struct page_info *page);
 
+/* Return the upper bound of MFNs, including hotplug memory. */
+unsigned long get_upper_mfn_bound(void);
+
 #include <asm/flushtlb.h>
 
 static inline void accumulate_tlbflush(bool *need_tlbflush,
-- 
2.12.3


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