[Xen-devel] [v3][PATCH 02/16] xen/x86/p2m: introduce set_identity_p2m_entry

[Tiejun Chen <tiejun.chen@xxxxxxxxx>]

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@xxxxxxxxx>
---
 xen/arch/x86/mm/p2m.c     | 35 +++++++++++++++++++++++++++++++++++
 xen/include/asm-x86/p2m.h |  4 ++++
 2 files changed, 39 insertions(+)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 1fd1194..a6db236 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -898,6 +898,41 @@ 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;
+
+    if ( paging_mode_translate(p2m->domain) )
+    {
+        gfn_lock(p2m, gfn, 0);
+
+        mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL);
+
+        if ( p2mt == p2m_invalid || mfn_x(mfn) == INVALID_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
+        {
+            ret = -EBUSY;
+            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;
+    }
+
+    return 0;
+}
+
 /* 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 b49c09b..95b6266 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -543,6 +543,10 @@ 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


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