[Xen-devel] [PATCH 02/24] xen: separate p2m allocation from setting

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>

When doing very early p2m setting, we need to separate setting
from allocation, so split things up accordingly.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   61 +++++++++++++++++++++++++++++++++++++--------------
 arch/x86/xen/mmu.h |    3 ++
 2 files changed, 47 insertions(+), 17 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index eceff87..d534986 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -233,47 +233,74 @@ unsigned long get_phys_to_machine(unsigned long pfn)
 }
 EXPORT_SYMBOL_GPL(get_phys_to_machine);
 
-static void alloc_p2m(unsigned long **pp, unsigned long *mfnp)
+/* install a  new p2m_top page */
+bool install_p2mtop_page(unsigned long pfn, unsigned long *p)
 {
-       unsigned long *p;
+       unsigned topidx = p2m_top_index(pfn);
+       unsigned long **pfnp, *mfnp;
        unsigned i;
 
-       p = (void *)__get_free_page(GFP_KERNEL | __GFP_NOFAIL);
-       BUG_ON(p == NULL);
+       pfnp = &p2m_top[topidx];
+       mfnp = &p2m_top_mfn[topidx];
 
        for (i = 0; i < P2M_ENTRIES_PER_PAGE; i++)
                p[i] = INVALID_P2M_ENTRY;
 
-       if (cmpxchg(pp, p2m_missing, p) != p2m_missing)
-               free_page((unsigned long)p);
-       else
+       if (cmpxchg(pfnp, p2m_missing, p) == p2m_missing) {
                *mfnp = virt_to_mfn(p);
+               return true;
+       }
+
+       return false;
 }
 
-void set_phys_to_machine(unsigned long pfn, unsigned long mfn)
+static void alloc_p2m(unsigned long pfn)
 {
-       unsigned topidx, idx;
+       unsigned long *p;
 
-       if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
-               BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
-               return;
-       }
+       p = (void *)__get_free_page(GFP_KERNEL | __GFP_NOFAIL);
+       BUG_ON(p == NULL);
+
+       if (!install_p2mtop_page(pfn, p))
+               free_page((unsigned long)p);
+}
+
+/* Try to install p2m mapping; fail if intermediate bits missing */
+bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
+{
+       unsigned topidx, idx;
 
        if (unlikely(pfn >= MAX_DOMAIN_PAGES)) {
                BUG_ON(mfn != INVALID_P2M_ENTRY);
-               return;
+               return true;
        }
 
        topidx = p2m_top_index(pfn);
        if (p2m_top[topidx] == p2m_missing) {
-               /* no need to allocate a page to store an invalid entry */
                if (mfn == INVALID_P2M_ENTRY)
-                       return;
-               alloc_p2m(&p2m_top[topidx], &p2m_top_mfn[topidx]);
+                       return true;
+               return false;
        }
 
        idx = p2m_index(pfn);
        p2m_top[topidx][idx] = mfn;
+
+       return true;
+}
+
+void 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;
+       }
+
+       if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
+               alloc_p2m(pfn);
+
+               if (!__set_phys_to_machine(pfn, mfn))
+                       BUG();
+       }
 }
 
 unsigned long arbitrary_virt_to_mfn(void *vaddr)
diff --git a/arch/x86/xen/mmu.h b/arch/x86/xen/mmu.h
index 24d1b44..da73026 100644
--- a/arch/x86/xen/mmu.h
+++ b/arch/x86/xen/mmu.h
@@ -11,6 +11,9 @@ enum pt_level {
 };
 
 
+bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn);
+bool install_p2mtop_page(unsigned long pfn, unsigned long *p);
+
 void set_pte_mfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags);
 
 
-- 
1.6.0.6


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