[Xen-devel] [PATCH 4/4] dmop: Add xendevicemodel_modified_memory_bulk()

[<jennifer.herbert@xxxxxxxxxx>]

From: Jennifer Herbert <Jennifer.Herbert@xxxxxxxxxx>

This new lib devicemodel call allows multiple extents of pages to be
marked as modified in a single call.  This is something needed for a
usecase I'm working on.

The xen side of the modified_memory call has been modified to accept
an array of extents.  The devicemodel library either provides an array
of length 1, to support the original library function, or a second
function allows an array to be provided.

Signed-off-by: Jennifer Herbert <Jennifer.Herbert@xxxxxxxxxx>
--
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
---
 tools/libs/devicemodel/core.c                   |  30 ++++--
 tools/libs/devicemodel/include/xendevicemodel.h |  19 +++-
 xen/arch/x86/hvm/dm.c                           | 117 ++++++++++++++++--------
 xen/include/public/hvm/dm_op.h                  |  19 +++-
 4 files changed, 134 insertions(+), 51 deletions(-)

diff --git a/tools/libs/devicemodel/core.c b/tools/libs/devicemodel/core.c
index ff09819..d7c6476 100644
--- a/tools/libs/devicemodel/core.c
+++ b/tools/libs/devicemodel/core.c
@@ -459,22 +459,36 @@ int xendevicemodel_track_dirty_vram(
                              dirty_bitmap, (size_t)(nr + 7) / 8);
 }
 
-int xendevicemodel_modified_memory(
-    xendevicemodel_handle *dmod, domid_t domid, uint64_t first_pfn,
-    uint32_t nr)
+int xendevicemodel_modified_memory_bulk(
+    xendevicemodel_handle *dmod, domid_t domid,
+    struct xen_dm_op_modified_memory_extent *extents, uint32_t nr)
 {
     struct xen_dm_op op;
-    struct xen_dm_op_modified_memory *data;
+    struct xen_dm_op_modified_memory *header;
+    size_t extents_size = nr * sizeof(struct xen_dm_op_modified_memory_extent);
 
     memset(&op, 0, sizeof(op));
 
     op.op = XEN_DMOP_modified_memory;
-    data = &op.u.modified_memory;
+    header = &op.u.modified_memory;
 
-    data->first_pfn = first_pfn;
-    data->nr = nr;
+    header->nr_extents = nr;
+    header->opaque = 0;
 
-    return xendevicemodel_op(dmod, domid, 1, &op, sizeof(op));
+    return xendevicemodel_op(dmod, domid, 2, &op, sizeof(op),
+                             extents, extents_size);
+}
+
+int xendevicemodel_modified_memory(
+    xendevicemodel_handle *dmod, domid_t domid, uint64_t first_pfn,
+    uint32_t nr)
+{
+    struct xen_dm_op_modified_memory_extent extent;
+
+    extent.first_pfn = first_pfn;
+    extent.nr = nr;
+
+    return xendevicemodel_modified_memory_bulk(dmod, domid, &extent, 1);
 }
 
 int xendevicemodel_set_mem_type(
diff --git a/tools/libs/devicemodel/include/xendevicemodel.h 
b/tools/libs/devicemodel/include/xendevicemodel.h
index 1da216f..580fad2 100644
--- a/tools/libs/devicemodel/include/xendevicemodel.h
+++ b/tools/libs/devicemodel/include/xendevicemodel.h
@@ -254,8 +254,8 @@ int xendevicemodel_track_dirty_vram(
     uint32_t nr, unsigned long *dirty_bitmap);
 
 /**
- * This function notifies the hypervisor that a set of domain pages
- * have been modified.
+ * This function notifies the hypervisor that a set of contiguous
+ * domain pages have been modified.
  *
  * @parm dmod a handle to an open devicemodel interface.
  * @parm domid the domain id to be serviced
@@ -268,6 +268,21 @@ int xendevicemodel_modified_memory(
     uint32_t nr);
 
 /**
+ * This function notifies the hypervisor that a set of discontiguous
+ * domain pages have been modified.
+ *
+ * @parm dmod a handle to an open devicemodel interface.
+ * @parm domid the domain id to be serviced
+ * @parm extents an array of extent structs, which each hold
+                 a start_pfn and nr (number of pfns).
+ * @parm nr the number of extents in the array
+ * @return 0 on success, -1 on failure.
+ */
+int xendevicemodel_modified_memory_bulk(
+    xendevicemodel_handle *dmod, domid_t domid,
+    struct xen_dm_op_modified_memory_extent extents[], uint32_t nr);
+
+/**
  * This function notifies the hypervisor that a set of domain pages
  * are to be treated in a specific way. (See the definition of
  * hvmmem_type_t).
diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
index 6990725..61df3cf 100644
--- a/xen/arch/x86/hvm/dm.c
+++ b/xen/arch/x86/hvm/dm.c
@@ -155,56 +155,102 @@ static int set_isa_irq_level(struct domain *d, uint8_t 
isa_irq,
 }
 
 static int modified_memory(struct domain *d,
-                           struct xen_dm_op_modified_memory *data)
+                           struct dmop_args *bufs,
+                           struct xen_dm_op_modified_memory *header)
 {
-    xen_pfn_t last_pfn = data->first_pfn + data->nr - 1;
-    unsigned int iter = 0;
-    int rc = 0;
+#define EXTENTS_BUFFER 1
 
-    if ( (data->first_pfn > last_pfn) ||
-         (last_pfn > domain_get_maximum_gpfn(d)) )
-        return -EINVAL;
+    /* Process maximum of 256 pfns before checking for continuation. */
+    const unsigned int cont_check_interval = 0x100;
+    unsigned int *rem_extents =  &header->nr_extents;
+    unsigned int batch_rem_pfns = cont_check_interval;
+    /* Used for continuation. */
+    unsigned int *pfns_done = &header->opaque;
 
     if ( !paging_mode_log_dirty(d) )
         return 0;
 
-    while ( iter < data->nr )
+    if ( (bufs->buf[EXTENTS_BUFFER].size /
+          sizeof(struct xen_dm_op_modified_memory_extent)) <
+         *rem_extents )
+        return -EINVAL;
+
+    while ( *rem_extents > 0 )
     {
-        unsigned long pfn = data->first_pfn + iter;
-        struct page_info *page;
+        struct xen_dm_op_modified_memory_extent extent;
+        unsigned int batch_nr;
+        xen_pfn_t pfn, end_pfn;
+        int rc;
+
+        rc = copy_from_guest_buf_offset(&extent,
+            bufs, EXTENTS_BUFFER, (*rem_extents - 1) * sizeof(extent));
+        if ( rc )
+            return -EFAULT;
+
+        if ( extent.pad )
+            return -EINVAL;
+
+        end_pfn = extent.first_pfn + extent.nr;
+
+        if ( end_pfn <= extent.first_pfn ||
+             end_pfn > domain_get_maximum_gpfn(d) )
+            return -EINVAL;
 
-        page = get_page_from_gfn(d, pfn, NULL, P2M_UNSHARE);
-        if ( page )
+        if ( *pfns_done >= extent.nr )
+            return -EINVAL;
+
+        pfn = extent.first_pfn + *pfns_done;
+        batch_nr = extent.nr - *pfns_done;
+
+        if ( batch_nr > batch_rem_pfns )
+        {
+            batch_nr = batch_rem_pfns;
+            *pfns_done += batch_nr;
+            end_pfn = pfn + batch_nr;
+        }
+        else
         {
-            mfn_t gmfn = _mfn(page_to_mfn(page));
-
-            paging_mark_dirty(d, gmfn);
-            /*
-             * These are most probably not page tables any more
-             * don't take a long time and don't die either.
-             */
-            sh_remove_shadows(d, gmfn, 1, 0);
-            put_page(page);
+            (*rem_extents)--;
+            *pfns_done = 0;
         }
 
-        iter++;
+        batch_rem_pfns -= batch_nr;
+
+        for ( ; pfn < end_pfn; pfn++ )
+        {
+            struct page_info *page;
+
+            page = get_page_from_gfn(d, pfn, NULL, P2M_UNSHARE);
+            if ( page )
+            {
+                mfn_t gmfn = _mfn(page_to_mfn(page));
+
+                paging_mark_dirty(d, gmfn);
+                /*
+                 * These are most probably not page tables any more
+                 * don't take a long time and don't die either.
+                 */
+                sh_remove_shadows(d, gmfn, 1, 0);
+                put_page(page);
+            }
+        }
 
         /*
-         * Check for continuation every 256th iteration and if the
-         * iteration is not the last.
+         * After a full batch of cont_check_interval pfns
+         * have been processed, and there are still extents
+         * remaining to process, check for continuation.
          */
-        if ( (iter < data->nr) && ((iter & 0xff) == 0) &&
-             hypercall_preempt_check() )
+        if ( (batch_rem_pfns == 0) && (*rem_extents > 0) )
         {
-            data->first_pfn += iter;
-            data->nr -= iter;
+            if ( hypercall_preempt_check() )
+                return -ERESTART;
 
-            rc = -ERESTART;
-            break;
+            batch_rem_pfns = cont_check_interval;
         }
     }
+    return 0;
 
-    return rc;
+#undef EXTENTS_BUFFER
 }
 
 static bool allow_p2m_type_change(p2m_type_t old, p2m_type_t new)
@@ -541,13 +587,8 @@ static int dm_op(struct dmop_args *op_args)
         struct xen_dm_op_modified_memory *data =
             &op.u.modified_memory;
 
-        const_op = false;
-
-        rc = -EINVAL;
-        if ( data->pad )
-            break;
-
-        rc = modified_memory(d, data);
+        rc = modified_memory(d, op_args, data);
+        const_op = !rc;
         break;
     }
 
diff --git a/xen/include/public/hvm/dm_op.h b/xen/include/public/hvm/dm_op.h
index 5ea79ef..20c21b6 100644
--- a/xen/include/public/hvm/dm_op.h
+++ b/xen/include/public/hvm/dm_op.h
@@ -237,13 +237,26 @@ struct xen_dm_op_set_pci_link_route {
  * XEN_DMOP_modified_memory: Notify that a set of pages were modified by
  *                           an emulator.
  *
- * NOTE: In the event of a continuation, 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.
+ * DMOP buf 1 contains an array of xen_dm_op_modified_memory_extent with
+ * @nr_extents entries.
+ *
+ * On error, @nr_extents will contain the index+1 of the extent that
+ * had the error.  It is not defined if or which pages may have been
+ * marked as dirty, in this event.
  */
 #define XEN_DMOP_modified_memory 11
 
 struct xen_dm_op_modified_memory {
+    /*
+     * IN - Number of extents to be processed
+     * OUT -returns n+1 for failing extent
+     */
+    uint32_t nr_extents;
+    /* IN/OUT - Must be set to 0 */
+    uint32_t opaque;
+};
+
+struct xen_dm_op_modified_memory_extent {
     /* IN - number of contiguous pages modified */
     uint32_t nr;
     uint32_t pad;
-- 
2.1.4


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