[Xen-devel] [PATCH v9 04/14] arch/arm: unmap partially-mapped I/O-memory regions

[Arianna Avanzini <avanzini.arianna@xxxxxxxxx>]

This commit changes the function apply_p2m_changes() to unwind changes
performed while mapping an I/O-memory region, if errors are seen during
the operation. This is useful to avoid that I/O-memory areas are
partially accessible to guests.

Signed-off-by: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
Cc: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
Cc: Paolo Valente <paolo.valente@xxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxxxxx>
Cc: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Cc: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Eric Trudeau <etrudeau@xxxxxxxxxxxx>
Cc: Viktor Kleinik <viktor.kleinik@xxxxxxxxxxxxxxx>

---

    v9:
        - Let apply_p2m_ranges() unwind its own progress instead of relying on
          the caller to unmap partially-mapped I/O-memory regions.

---
 xen/arch/arm/p2m.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 22646e9..92fc4ec 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -314,7 +314,7 @@ static int apply_p2m_changes(struct domain *d,
     unsigned long cur_first_page = ~0,
                   cur_first_offset = ~0,
                   cur_second_offset = ~0;
-    unsigned long count = 0;
+    unsigned long count = 0, inserted = 0;
     unsigned int flush = 0;
     bool_t populate = (op == INSERT || op == ALLOCATE);
     lpae_t pte;
@@ -328,6 +328,7 @@ static int apply_p2m_changes(struct domain *d,
 
     spin_lock(&p2m->lock);
 
+unwind:
     addr = start_gpaddr;
     while ( addr < end_gpaddr )
     {
@@ -338,7 +339,9 @@ static int apply_p2m_changes(struct domain *d,
             if ( !first )
             {
                 rc = -EINVAL;
-                goto out;
+                end_gpaddr = start_gpaddr + inserted * PAGE_SIZE;
+                op = REMOVE;
+                goto unwind;
             }
             cur_first_page = p2m_first_level_index(addr);
         }
@@ -357,7 +360,9 @@ static int apply_p2m_changes(struct domain *d,
             if ( rc < 0 )
             {
                 printk("p2m_populate_ram: L1 failed\n");
-                goto out;
+                end_gpaddr = start_gpaddr + inserted * PAGE_SIZE;
+                op = REMOVE;
+                goto unwind;
             }
         }
 
@@ -384,7 +389,9 @@ static int apply_p2m_changes(struct domain *d,
                                   flush_pt);
             if ( rc < 0 ) {
                 printk("p2m_populate_ram: L2 failed\n");
-                goto out;
+                end_gpaddr = start_gpaddr + inserted * PAGE_SIZE;
+                op = REMOVE;
+                goto unwind;
             }
         }
 
@@ -441,6 +448,7 @@ static int apply_p2m_changes(struct domain *d,
                     pte = mfn_to_p2m_entry(maddr >> PAGE_SHIFT, mattr, t);
                     p2m_write_pte(&third[third_table_offset(addr)],
                                   pte, flush_pt);
+                    inserted++;
                 }
                 break;
             case REMOVE:
-- 
1.9.3


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