xen: Mark all initial reserved pages for the balloon as INVALID_P2M_ENTRY.

With this patch, we diligently set regions that will be used by the
balloon driver to be INVALID_P2M_ENTRY and under the ownership
of the balloon driver. We are OK using the __set_phys_to_machine
as we do not expect to be allocating any P2M middle or entries pages.
The set_phys_to_machine has the side-effect of potentially allocating
new pages and we do not want that at this stage.

We can do this because xen_build_mfn_list_list will have already
allocated all such pages up to xen_max_p2m_pfn.

We also move the check for auto translated physmap down the
stack so it is present in __set_phys_to_machine.

[v2: Rebased with mmu->p2m code split]
Reviewed-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

4 files changed, 12 insertions, 7 deletions

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index f25bdf238a33..8ea977277c55 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -41,6 +41,7 @@ extern unsigned int   machine_to_phys_order;
 
 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);
 
 extern int m2p_add_override(unsigned long mfn, struct page *page);
 extern int m2p_remove_override(struct page *page);
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 5e92b61ad574..0180ae88307b 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -2074,7 +2074,7 @@ static void xen_zap_pfn_range(unsigned long vaddr, unsigned int order,
                         in_frames[i] = virt_to_mfn(vaddr);
 
                 MULTI_update_va_mapping(mcs.mc, vaddr, VOID_PTE, 0);
-                set_phys_to_machine(virt_to_pfn(vaddr), INVALID_P2M_ENTRY);
+                __set_phys_to_machine(virt_to_pfn(vaddr), INVALID_P2M_ENTRY);
 
                 if (out_frames)
                         out_frames[i] = virt_to_pfn(vaddr);
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index ddc81a06edb9..df4e36775339 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -365,6 +365,10 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
         unsigned topidx, mididx, idx;
 
+        if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
+                BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
+                return true;
+        }
         if (unlikely(pfn >= MAX_P2M_PFN)) {
                 BUG_ON(mfn != INVALID_P2M_ENTRY);
                 return true;
@@ -384,11 +388,6 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 
 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 {
-        if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
-                BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
-                return true;
-        }
-
         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
                 if (!alloc_p2m(pfn))
                         return false;
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index b5a7f928234b..7201800e55a4 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -52,6 +52,8 @@ phys_addr_t xen_extra_mem_start, xen_extra_mem_size;
 
 static __init void xen_add_extra_mem(unsigned long pages)
 {
+        unsigned long pfn;
+
         u64 size = (u64)pages * PAGE_SIZE;
         u64 extra_start = xen_extra_mem_start + xen_extra_mem_size;
 
@@ -66,6 +68,9 @@ static __init void xen_add_extra_mem(unsigned long pages)
         xen_extra_mem_size += size;
 
         xen_max_p2m_pfn = PFN_DOWN(extra_start + size);
+
+        for (pfn = PFN_DOWN(extra_start); pfn <= xen_max_p2m_pfn; pfn++)
+                __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 }
 
 static unsigned long __init xen_release_chunk(phys_addr_t start_addr,
@@ -104,7 +109,7 @@ static unsigned long __init xen_release_chunk(phys_addr_t start_addr,
                 WARN(ret != 1, "Failed to release memory %lx-%lx err=%d\n",
                      start, end, ret);
                 if (ret == 1) {
-                        set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+                        __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
                         len++;
                 }
         }