[Xen-devel] [PATCH 2/2] xen:p2m: Create entries in the P2M_MFN trees's to track 1-1 mappings

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

. when applicable. We need to track in the p2m_mfn and
p2m_mfn_p the MFNs and pointers, respectivly, for the P2M entries
that are allocated for the identity mappings. Without this,
a PV domain with an E820 that triggers the 1-1 mapping to kick in,
won't be able to be restored as the P2M won't have the identity
mappings.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/p2m.c |   30 ++++++++++++++++++++++++++++--
 1 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 141eb0d..a01e653 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -522,11 +522,20 @@ static bool __init __early_alloc_p2m(unsigned long pfn)
        /* Boundary cross-over for the edges: */
        if (idx) {
                unsigned long *p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
+               unsigned long *mid_mfn_p;
 
                p2m_init(p2m);
 
                p2m_top[topidx][mididx] = p2m;
 
+               /* For save/restore we need to MFN of the P2M saved */
+               
+               mid_mfn_p = p2m_top_mfn_p[topidx];
+               WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
+                       "P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
+                       topidx, mididx);
+               mid_mfn_p[mididx] = virt_to_mfn(p2m);
+
        }
        return idx != 0;
 }
@@ -549,12 +558,29 @@ unsigned long __init set_phys_range_identity(unsigned 
long pfn_s,
                pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE)
        {
                unsigned topidx = p2m_top_index(pfn);
-               if (p2m_top[topidx] == p2m_mid_missing) {
-                       unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
+               unsigned long *mid_mfn_p;
+               unsigned long **mid;
+
+               mid = p2m_top[topidx];
+               mid_mfn_p = p2m_top_mfn_p[topidx];
+               if (mid == p2m_mid_missing) {
+                       mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
 
                        p2m_mid_init(mid);
 
                        p2m_top[topidx] = mid;
+
+                       BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
+               }
+               /* And the save/restore P2M tables.. */
+               if (mid_mfn_p == p2m_mid_missing_mfn) {
+                       mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
+                       p2m_mid_mfn_init(mid_mfn_p);
+
+                       p2m_top_mfn_p[topidx] = mid_mfn_p;
+                       p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
+                       /* Note: we don't set mid_mfn_p[midix] here,
+                        * look in __early_alloc_p2m */
                }
        }
 
-- 
1.7.1


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