[Xen-devel] [PATCH v4 08/11] xen/arm: Handle remove foreign mapping

[Julien Grall <julien.grall@xxxxxxxxxx>]

Introduce p2m_remove_foreign to remove foreign mapping. This function will
will release the reference taken when the mapping is added in the p2m.

As the function is not yet implemented on x86, add stubs.

Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> [common/memory.c]
Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>

---
    Changes in v4:
        - Split patch #6 from dom0 pvh series v6.2 to retrieve only common
        code.
        - Rework commit title
        - Rename xen_rem_foreign_from_p2m in p2m_remove_foreign
        - Get the mfn from the pte. We are not sure that maddr given in
        parameters is valid
    Changes in v3:
        - Move put_page in create_p2m_entries
        - Move xenmem_rem_foreign_from_p2m in arch/arm/p2m.c
    Changes in v2:
        - Introduce the patch
---
 xen/arch/arm/p2m.c        |   25 +++++++++++++++++++++++--
 xen/common/memory.c       |   12 +++++++++++-
 xen/include/asm-arm/p2m.h |    2 ++
 xen/include/asm-x86/p2m.h |    6 ++++++
 4 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 39d8a03..cfdc19c 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -317,10 +317,21 @@ static int create_p2m_entries(struct domain *d,
                 break;
             case REMOVE:
                 {
-                    lpae_t pte;
+                    lpae_t pte = third[third_table_offset(addr)];
+                    unsigned long mfn;
+
+                    maddr = (pte.bits & PADDR_MASK & PAGE_MASK);
+                    mfn = paddr_to_pfn(maddr);
+
+                    /* TODO: Handle other p2m type */
+                    if ( pte.p2m.valid && p2m_is_foreign(pte.p2m.type) )
+                    {
+                        ASSERT(mfn_valid(mfn));
+                        put_page(mfn_to_page(mfn));
+                    }
+
                     memset(&pte, 0x00, sizeof(pte));
                     write_pte(&third[third_table_offset(addr)], pte);
-                    maddr += PAGE_SIZE;
                 }
                 break;
         }
@@ -380,6 +391,16 @@ void guest_physmap_remove_page(struct domain *d,
                        pfn_to_paddr(mfn), MATTR_MEM, p2m_invalid);
 }
 
+int p2m_remove_foreign(struct domain *d, unsigned long gpfn)
+{
+    unsigned long mfn = gmfn_to_mfn(d, gpfn);
+
+    ASSERT(mfn_valid(mfn));
+    guest_physmap_remove_page(d, gpfn, mfn, 0);
+
+    return 0;
+}
+
 int p2m_alloc_table(struct domain *d)
 {
     struct p2m_domain *p2m = &d->arch.p2m;
diff --git a/xen/common/memory.c b/xen/common/memory.c
index eb7b72b..61791a4 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -678,6 +678,7 @@ long do_memory_op(unsigned long cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
         struct xen_remove_from_physmap xrfp;
         struct page_info *page;
         struct domain *d;
+        p2m_type_t p2mt;
 
         if ( copy_from_guest(&xrfp, arg, 1) )
             return -EFAULT;
@@ -693,12 +694,21 @@ long do_memory_op(unsigned long cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
             return rc;
         }
 
-        page = get_page_from_gfn(d, xrfp.gpfn, NULL, P2M_ALLOC);
+        /*
+         * If autotranslate guest, (eg pvh), the gfn could be mapped to a mfn
+         * from foreign domain by the user space tool during domain creation.
+         * We need to check for that, free it up from the p2m, and release
+         * refcnt on it. In such a case, page would be NULL and the following
+         * call would not have refcnt'd the page.
+         */
+        page = get_page_from_gfn(d, xrfp.gpfn, &p2mt, P2M_ALLOC);
         if ( page )
         {
             guest_physmap_remove_page(d, xrfp.gpfn, page_to_mfn(page), 0);
             put_page(page);
         }
+        else if ( p2m_is_foreign(p2mt) )
+            rc = p2m_remove_foreign(d, xrfp.gpfn);
         else
             rc = -ENOENT;
 
diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
index 0eb07a8..844ef9d 100644
--- a/xen/include/asm-arm/p2m.h
+++ b/xen/include/asm-arm/p2m.h
@@ -144,6 +144,8 @@ static inline int get_page_and_type(struct page_info *page,
     return rc;
 }
 
+int p2m_remove_foreign(struct domain *d, unsigned long gpfn);
+
 #endif /* _XEN_P2M_H */
 
 /*
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index d5d6391..9288043 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -515,6 +515,12 @@ int clear_mmio_p2m_entry(struct domain *d, unsigned long 
gfn);
 /* Set foreign mfn in the current guest's p2m table. */
 int set_foreign_p2m_entry(struct domain *domp, unsigned long gfn, mfn_t mfn);
 
+/* Remove foreign mapping from the guest's p2m table. */
+static inline int p2m_remove_foreign(struct domain *d, unsigned long gpfn)
+{
+    return -ENOSYS;
+}
+
 /* 
  * Populate-on-demand
  */
-- 
1.7.10.4


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