[RFC][PATCH 05/13] xen/x86/p2m: introduce set_identity_p2m_entry

[Tiejun Chen <tiejun.chen@intel.com>]

We will create this sort of identity mapping as follows:

If the gfn space is unoccupied, we just set the mapping. If the space
is already occupied by 1:1 mappings, do nothing. Failed for any
other cases.

Signed-off-by: Tiejun Chen <tiejun.chen@intel.com>
---
 xen/arch/x86/mm/p2m.c     | 30 ++++++++++++++++++++++++++++++
 xen/include/asm-x86/p2m.h |  4 ++++
 2 files changed, 34 insertions(+)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 6a06e9f..d98730c 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -862,6 +862,36 @@ int set_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn,
     return set_typed_p2m_entry(d, gfn, mfn, p2m_mmio_direct, access);
 }
 
+int set_identity_p2m_entry(struct domain *d, unsigned long gfn,
+                           p2m_access_t p2ma)
+{
+    p2m_type_t p2mt;
+    p2m_access_t a;
+    mfn_t mfn;
+    struct p2m_domain *p2m = p2m_get_hostp2m(d);
+    int ret = -EBUSY;
+
+    gfn_lock(p2m, gfn, 0);
+
+    mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL);
+
+    if ( !mfn_valid(mfn) )
+        ret = p2m_set_entry(p2m, gfn, _mfn(gfn), PAGE_ORDER_4K, p2m_mmio_direct,
+                            p2ma);
+    else if ( mfn_x(mfn) == gfn && p2mt == p2m_mmio_direct && a == p2ma )
+        ret = 0;
+    else
+    {
+        printk(XENLOG_G_WARNING
+               "Cannot identity map d%d:%lx, already mapped to %lx.\n",
+               d->domain_id, gfn, mfn_x(mfn));
+    }
+
+    gfn_unlock(p2m, gfn, 0);
+
+    return ret;
+}
+
 /* Returns: 0 for success, -errno for failure */
 int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn)
 {
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index e93c551..a9c0415 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -532,6 +532,10 @@ int set_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn,
                        p2m_access_t access);
 int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn);
 
+/* Set identity addresses in the p2m table (for pass-through) */
+int set_identity_p2m_entry(struct domain *d, unsigned long gfn,
+                           p2m_access_t p2ma);
+
 /* Add foreign mapping to the guest's p2m table. */
 int p2m_add_foreign(struct domain *tdom, unsigned long fgfn,
                     unsigned long gpfn, domid_t foreign_domid);
-- 
1.9.1