x86/xen: export xen_alloc_p2m_entry()

Rename alloc_p2m() to xen_alloc_p2m_entry() and export it.

This is useful for ensuring that a p2m entry is allocated (i.e., not a
shared missing or identity entry) so that subsequent set_phys_to_machine()
calls will require no further allocations.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
v3:
- Make xen_alloc_p2m_entry() a nop on auto-xlate guests.

2 files changed, 15 insertions, 6 deletions

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 0679e11d2cf7..b922fa4bb4a1 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -43,6 +43,8 @@ extern unsigned long *xen_p2m_addr;
 extern unsigned long  xen_p2m_size;
 extern unsigned long  xen_max_p2m_pfn;
 
+extern int xen_alloc_p2m_entry(unsigned long pfn);
+
 extern unsigned long get_phys_to_machine(unsigned long pfn);
 extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 extern bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 660b3cfef234..cab9f766bb06 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -530,7 +530,7 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
  * the new pages are installed with cmpxchg; if we lose the race then
  * simply free the page we allocated and use the one that's there.
  */
-static bool alloc_p2m(unsigned long pfn)
+int xen_alloc_p2m_entry(unsigned long pfn)
 {
         unsigned topidx;
         unsigned long *top_mfn_p, *mid_mfn;
@@ -540,6 +540,9 @@ static bool alloc_p2m(unsigned long pfn)
         unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
         unsigned long p2m_pfn;
 
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+                return 0;
+
         ptep = lookup_address(addr, &level);
         BUG_ON(!ptep || level != PG_LEVEL_4K);
         pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
@@ -548,7 +551,7 @@ static bool alloc_p2m(unsigned long pfn)
                 /* PMD level is missing, allocate a new one */
                 ptep = alloc_p2m_pmd(addr, pte_pg);
                 if (!ptep)
-                        return false;
+                        return -ENOMEM;
         }
 
         if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
@@ -566,7 +569,7 @@ static bool alloc_p2m(unsigned long pfn)
 
                         mid_mfn = alloc_p2m_page();
                         if (!mid_mfn)
-                                return false;
+                                return -ENOMEM;
 
                         p2m_mid_mfn_init(mid_mfn, p2m_missing);
 
@@ -592,7 +595,7 @@ static bool alloc_p2m(unsigned long pfn)
 
                 p2m = alloc_p2m_page();
                 if (!p2m)
-                        return false;
+                        return -ENOMEM;
 
                 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
                         p2m_init(p2m);
@@ -625,8 +628,9 @@ static bool alloc_p2m(unsigned long pfn)
                 HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
         }
 
-        return true;
+        return 0;
 }
+EXPORT_SYMBOL(xen_alloc_p2m_entry);
 
 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
                                       unsigned long pfn_e)
@@ -688,7 +692,10 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
         if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
-                if (!alloc_p2m(pfn))
+                int ret;
+
+                ret = xen_alloc_p2m_entry(pfn);
+                if (ret < 0)
                         return false;
 
                 return __set_phys_to_machine(pfn, mfn);