[PATCH v2 5/8] dm_op: convert HVMOP_modified_memory

[Paul Durrant <paul.durrant@citrix.com>]

This patch introduces code to handle DMOP continuations.

NOTE: This patch also modifies the type of the 'nr' argument of
      xc_hvm_modified_memory() from uint64_t to uint32_t. In practice the
      value passed was always truncated to 32 bits.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Daniel De Graaf <dgdegra@tycho.nsa.gov>

v2:
- Addressed several comments from Jan, including...
- Added explanatory note on continuation handling
---
 tools/libxc/include/xenctrl.h       |  2 +-
 tools/libxc/xc_misc.c               | 27 +++++--------
 xen/arch/x86/hvm/dm.c               | 81 ++++++++++++++++++++++++++++++++++++-
 xen/arch/x86/hvm/hvm.c              | 60 ---------------------------
 xen/include/public/hvm/dm_op.h      | 19 +++++++++
 xen/include/public/hvm/hvm_op.h     | 13 ------
 xen/xsm/flask/policy/access_vectors |  2 +-
 7 files changed, 110 insertions(+), 94 deletions(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index db04848..9950690 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -1627,7 +1627,7 @@ int xc_hvm_track_dirty_vram(
  * Notify that some pages got modified by the Device Model
  */
 int xc_hvm_modified_memory(
-    xc_interface *xch, domid_t dom, uint64_t first_pfn, uint64_t nr);
+    xc_interface *xch, domid_t dom, uint64_t first_pfn, uint32_t nr);
 
 /*
  * Set a range of memory to a specific type.
diff --git a/tools/libxc/xc_misc.c b/tools/libxc/xc_misc.c
index ddea2bb..597df99 100644
--- a/tools/libxc/xc_misc.c
+++ b/tools/libxc/xc_misc.c
@@ -573,29 +573,20 @@ int xc_hvm_track_dirty_vram(
 }
 
 int xc_hvm_modified_memory(
-    xc_interface *xch, domid_t dom, uint64_t first_pfn, uint64_t nr)
+    xc_interface *xch, domid_t dom, uint64_t first_pfn, uint32_t nr)
 {
-    DECLARE_HYPERCALL_BUFFER(struct xen_hvm_modified_memory, arg);
-    int rc;
-
-    arg = xc_hypercall_buffer_alloc(xch, arg, sizeof(*arg));
-    if ( arg == NULL )
-    {
-        PERROR("Could not allocate memory for xc_hvm_modified_memory hypercall");
-        return -1;
-    }
+    struct xen_dm_op op;
+    struct xen_dm_op_modified_memory *data;
 
-    arg->domid     = dom;
-    arg->first_pfn = first_pfn;
-    arg->nr        = nr;
+    memset(&op, 0, sizeof(op));
 
-    rc = xencall2(xch->xcall, __HYPERVISOR_hvm_op,
-                  HVMOP_modified_memory,
-                  HYPERCALL_BUFFER_AS_ARG(arg));
+    op.op = XEN_DMOP_modified_memory;
+    data = &op.u.modified_memory;
 
-    xc_hypercall_buffer_free(xch, arg);
+    data->first_pfn = first_pfn;
+    data->nr = nr;
 
-    return rc;
+    return do_dm_op(xch, dom, 1, &op, sizeof(op));
 }
 
 int xc_hvm_set_mem_type(
diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
index 06bace0..4e7d8f9 100644
--- a/xen/arch/x86/hvm/dm.c
+++ b/xen/arch/x86/hvm/dm.c
@@ -14,6 +14,7 @@
  * this program; If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <xen/event.h>
 #include <xen/guest_access.h>
 #include <xen/hypercall.h>
 #include <xen/sched.h>
@@ -142,18 +143,77 @@ static int set_isa_irq_level(struct domain *d, uint8_t isa_irq,
     return 0;
 }
 
+static int modified_memory(struct domain *d, xen_pfn_t *first_pfn,
+                           unsigned int *nr)
+{
+    xen_pfn_t last_pfn = *first_pfn + *nr - 1;
+    unsigned int iter;
+    int rc;
+
+    if ( (*first_pfn > last_pfn) ||
+         (last_pfn > domain_get_maximum_gpfn(d)) )
+        return -EINVAL;
+
+    if ( !paging_mode_log_dirty(d) )
+        return 0;
+
+    iter = 0;
+    rc = 0;
+    while ( iter < *nr )
+    {
+        unsigned long pfn = *first_pfn + iter;
+        struct page_info *page;
+
+        page = get_page_from_gfn(d, pfn, NULL, P2M_UNSHARE);
+        if ( page )
+        {
+            paging_mark_dirty(d, page_to_mfn(page));
+            /*
+             * These are most probably not page tables any more
+             * don't take a long time and don't die either.
+             */
+            sh_remove_shadows(d, _mfn(page_to_mfn(page)), 1, 0);
+            put_page(page);
+        }
+
+        iter++;
+
+        /*
+         * Check for continuation every 256th iteration and if the
+         * iteration is not the last.
+         */
+        if ( (iter < *nr) && ((iter & 0xff) == 0) &&
+             hypercall_preempt_check() )
+        {
+            rc = -ERESTART;
+            break;
+        }
+    }
+
+    if ( rc == -ERESTART )
+    {
+        *first_pfn += iter;
+        *nr -= iter;
+    }
+
+    return rc;
+}
+
 long do_dm_op(domid_t domid,
               unsigned int nr_bufs,
               XEN_GUEST_HANDLE_PARAM(xen_dm_op_buf_t) bufs)
 {
     struct domain *d;
     struct xen_dm_op op;
+    bool restart;
     long rc;
 
     rc = rcu_lock_remote_domain_by_id(domid, &d);
     if ( rc )
         return rc;
 
+    restart = false;
+
     if ( !has_hvm_container_domain(d) )
         goto out;
 
@@ -311,17 +371,36 @@ long do_dm_op(domid_t domid,
         break;
     }
 
+    case XEN_DMOP_modified_memory:
+    {
+        struct xen_dm_op_modified_memory *data =
+            &op.u.modified_memory;
+
+        rc = -EINVAL;
+        if ( data->pad )
+            break;
+
+        rc = modified_memory(d, &data->first_pfn, &data->nr);
+        break;
+    }
+
     default:
         rc = -EOPNOTSUPP;
         break;
     }
 
-    if ( !rc )
+    if ( rc == -ERESTART )
+        restart = true;
+
+    if ( !rc || restart )
         rc = copy_buf_to_guest(bufs, nr_bufs, 0, &op, sizeof(op));
 
  out:
     rcu_unlock_domain(d);
 
+    if ( !rc && restart )
+        rc = hypercall_create_continuation(__HYPERVISOR_dm_op, "iih",
+                                           domid, nr_bufs, bufs);
     return rc;
 }
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index b336840..3760e0b 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -5385,7 +5385,6 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
     default:
         mask = ~0UL;
         break;
-    case HVMOP_modified_memory:
     case HVMOP_set_mem_type:
         mask = HVMOP_op_mask;
         break;
@@ -5418,65 +5417,6 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
         rc = guest_handle_is_null(arg) ? hvmop_flush_tlb_all() : -EINVAL;
         break;
 
-    case HVMOP_modified_memory:
-    {
-        struct xen_hvm_modified_memory a;
-        struct domain *d;
-
-        if ( copy_from_guest(&a, arg, 1) )
-            return -EFAULT;
-
-        rc = rcu_lock_remote_domain_by_id(a.domid, &d);
-        if ( rc != 0 )
-            return rc;
-
-        rc = -EINVAL;
-        if ( !is_hvm_domain(d) )
-            goto modmem_fail;
-
-        rc = xsm_hvm_control(XSM_DM_PRIV, d, op);
-        if ( rc )
-            goto modmem_fail;
-
-        rc = -EINVAL;
-        if ( a.nr < start_iter ||
-             ((a.first_pfn + a.nr - 1) < a.first_pfn) ||
-             ((a.first_pfn + a.nr - 1) > domain_get_maximum_gpfn(d)) )
-            goto modmem_fail;
-
-        rc = 0;
-        if ( !paging_mode_log_dirty(d) )
-            goto modmem_fail;
-
-        while ( a.nr > start_iter )
-        {
-            unsigned long pfn = a.first_pfn + start_iter;
-            struct page_info *page;
-
-            page = get_page_from_gfn(d, pfn, NULL, P2M_UNSHARE);
-            if ( page )
-            {
-                paging_mark_dirty(d, page_to_mfn(page));
-                /* These are most probably not page tables any more */
-                /* don't take a long time and don't die either */
-                sh_remove_shadows(d, _mfn(page_to_mfn(page)), 1, 0);
-                put_page(page);
-            }
-
-            /* Check for continuation if it's not the last interation */
-            if ( a.nr > ++start_iter && !(start_iter & HVMOP_op_mask) &&
-                 hypercall_preempt_check() )
-            {
-                rc = -ERESTART;
-                break;
-            }
-        }
-
-    modmem_fail:
-        rcu_unlock_domain(d);
-        break;
-    }
-
     case HVMOP_get_mem_type:
         rc = hvmop_get_mem_type(
             guest_handle_cast(arg, xen_hvm_get_mem_type_t));
diff --git a/xen/include/public/hvm/dm_op.h b/xen/include/public/hvm/dm_op.h
index 5751411..1a1b784 100644
--- a/xen/include/public/hvm/dm_op.h
+++ b/xen/include/public/hvm/dm_op.h
@@ -233,6 +233,24 @@ struct xen_dm_op_set_pci_link_route {
     uint16_t pad;
 };
 
+/*
+ * XEN_DMOP_modified_memory: Notify that a set of pages were modified by
+ *                           an emulator.
+ *
+ * NOTE: In the event of a continuation (return code -ERESTART), the
+ *       @first_pfn is set to the value of the pfn of the remaining
+ *       set of pages and @nr reduced to the size of the remaining set.
+ */
+#define XEN_DMOP_modified_memory 11
+
+struct xen_dm_op_modified_memory {
+    /* IN - number of contiguous pages modified */
+    uint32_t nr;
+    uint32_t pad;
+    /* IN - first pfn modified */
+    uint64_aligned_t first_pfn;
+};
+
 
 struct xen_dm_op {
     uint32_t op;
@@ -248,6 +266,7 @@ struct xen_dm_op {
         struct xen_dm_op_set_pci_intx_level set_pci_intx_level;
         struct xen_dm_op_set_isa_irq_level set_isa_irq_level;
         struct xen_dm_op_set_pci_link_route set_pci_link_route;
+        struct xen_dm_op_modified_memory modified_memory;
     } u;
 };
 
diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
index 7cf8d4d..76e1b78 100644
--- a/xen/include/public/hvm/hvm_op.h
+++ b/xen/include/public/hvm/hvm_op.h
@@ -99,19 +99,6 @@ typedef enum {
 /* Following tools-only interfaces may change in future. */
 #if defined(__XEN__) || defined(__XEN_TOOLS__)
 
-/* Notify that some pages got modified by the Device Model. */
-#define HVMOP_modified_memory    7
-struct xen_hvm_modified_memory {
-    /* Domain to be updated. */
-    domid_t  domid;
-    /* Number of pages. */
-    uint32_t nr;
-    /* First pfn. */
-    uint64_aligned_t first_pfn;
-};
-typedef struct xen_hvm_modified_memory xen_hvm_modified_memory_t;
-DEFINE_XEN_GUEST_HANDLE(xen_hvm_modified_memory_t);
-
 #define HVMOP_set_mem_type    8
 /* Notify that a region of memory is to be treated in a specific way. */
 struct xen_hvm_set_mem_type {
diff --git a/xen/xsm/flask/policy/access_vectors b/xen/xsm/flask/policy/access_vectors
index 708cfe6..2041ca5 100644
--- a/xen/xsm/flask/policy/access_vectors
+++ b/xen/xsm/flask/policy/access_vectors
@@ -260,7 +260,7 @@ class hvm
     bind_irq
 # XEN_DOMCTL_pin_mem_cacheattr
     cacheattr
-# HVMOP_modified_memory, HVMOP_get_mem_type, HVMOP_set_mem_type,
+# HVMOP_get_mem_type, HVMOP_set_mem_type,
 # HVMOP_set_mem_access, HVMOP_get_mem_access, HVMOP_pagetable_dying,
 # HVMOP_inject_trap
     hvmctl
-- 
2.1.4


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