[Xen-devel] [PATCH v13 10/11] common: add a new mappable resource type: XENMEM_resource_grant_table

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

This patch allows grant table frames to be mapped using the
XENMEM_acquire_resource memory op.

NOTE: This patch expands the on-stack mfn_list array in acquire_resource()
      but it is still small enough to remain on-stack.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>

v13:
 - Re-work the internals to avoid using the XENMAPIDX_grant_table_status
   hack.

v12:
 - Dropped limit checks as requested by Jan.

v10:
 - Addressed comments from Jan.

v8:
 - The functionality was originally incorporated into the earlier patch
   "x86/mm: add HYPERVISOR_memory_op to acquire guest resources".
---
 xen/common/grant_table.c      | 63 +++++++++++++++++++++++++++++++++++++------
 xen/common/memory.c           | 45 ++++++++++++++++++++++++++++++-
 xen/include/public/memory.h   |  6 +++++
 xen/include/xen/grant_table.h |  4 +++
 4 files changed, 109 insertions(+), 9 deletions(-)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 0558de9ce8..429c421cd9 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -3761,21 +3761,21 @@ int mem_sharing_gref_to_gfn(struct grant_table *gt, 
grant_ref_t ref,
 }
 #endif
 
-int gnttab_map_frame(struct domain *d, unsigned long idx, gfn_t gfn,
-                     mfn_t *mfn)
+/* Caller must hold write lock as version may change and table may grow */
+static int gnttab_get_frame(struct domain *d, bool is_status,
+                            unsigned long idx, mfn_t *mfn)
 {
-    int rc = 0;
     struct grant_table *gt = d->grant_table;
-
-    grant_write_lock(gt);
+    int rc = 0;
 
     if ( gt->gt_version == 0 )
         gt->gt_version = 1;
 
-    if ( gt->gt_version == 2 &&
-         (idx & XENMAPIDX_grant_table_status) )
+    if ( is_status )
     {
-        idx &= ~XENMAPIDX_grant_table_status;
+        if ( gt->gt_version != 2 )
+            return -EINVAL;
+
         if ( idx < nr_status_frames(gt) )
             *mfn = _mfn(virt_to_mfn(gt->status[idx]));
         else
@@ -3792,6 +3792,25 @@ int gnttab_map_frame(struct domain *d, unsigned long 
idx, gfn_t gfn,
             rc = -EINVAL;
     }
 
+    return rc;
+}
+
+int gnttab_map_frame(struct domain *d, unsigned long idx, gfn_t gfn,
+                     mfn_t *mfn)
+{
+    struct grant_table *gt = d->grant_table;
+    bool is_status = false;
+    int rc;
+
+    grant_write_lock(gt);
+
+    if ( idx & XENMAPIDX_grant_table_status )
+    {
+        is_status = true;
+        idx &= ~XENMAPIDX_grant_table_status;
+    }
+
+    rc = gnttab_get_frame(d, is_status, idx, mfn);
     if ( !rc )
         gnttab_set_frame_gfn(gt, idx, gfn);
 
@@ -3800,6 +3819,34 @@ int gnttab_map_frame(struct domain *d, unsigned long 
idx, gfn_t gfn,
     return rc;
 }
 
+int gnttab_get_grant_frame(struct domain *d, unsigned long idx,
+                           mfn_t *mfn)
+{
+    struct grant_table *gt = d->grant_table;
+    int rc;
+
+    /* write lock required as version may change and/or table may grow */
+    grant_write_lock(gt);
+    rc = gnttab_get_frame(d, false, idx, mfn);
+    grant_write_unlock(gt);
+
+    return rc;
+}
+
+int gnttab_get_status_frame(struct domain *d, unsigned long idx,
+                            mfn_t *mfn)
+{
+    struct grant_table *gt = d->grant_table;
+    int rc;
+
+    /* write lock required as version may change and/or table may grow */
+    grant_write_lock(gt);
+    rc = gnttab_get_frame(d, true, idx, mfn);
+    grant_write_unlock(gt);
+
+    return rc;
+}
+
 static void gnttab_usage_print(struct domain *rd)
 {
     int first = 1;
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 1c6932fd85..8097d85be3 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -23,6 +23,7 @@
 #include <xen/numa.h>
 #include <xen/mem_access.h>
 #include <xen/trace.h>
+#include <xen/grant_table.h>
 #include <asm/current.h>
 #include <asm/hardirq.h>
 #include <asm/p2m.h>
@@ -965,6 +966,43 @@ static long xatp_permission_check(struct domain *d, 
unsigned int space)
     return xsm_add_to_physmap(XSM_TARGET, current->domain, d);
 }
 
+static int acquire_grant_table(struct domain *d, unsigned int id,
+                               unsigned long frame,
+                               unsigned int nr_frames,
+                               xen_pfn_t mfn_list[])
+{
+    unsigned int i = nr_frames;
+
+    /* Iterate backwards in case table needs to grow */
+    while ( i-- != 0 )
+    {
+        mfn_t mfn = INVALID_MFN;
+        int rc;
+
+        switch ( id )
+        {
+        case XENMEM_resource_grant_table_id_grant:
+            rc = gnttab_get_grant_frame(d, frame + i, &mfn);
+            break;
+
+        case XENMEM_resource_grant_table_id_status:
+            rc = gnttab_get_status_frame(d, frame + i, &mfn);
+            break;
+
+        default:
+            rc = -EINVAL;
+            break;
+        }
+
+        if ( rc )
+            return rc;
+
+        mfn_list[i] = mfn_x(mfn);
+    }
+
+    return 0;
+}
+
 static int acquire_resource(
     XEN_GUEST_HANDLE_PARAM(xen_mem_acquire_resource_t) arg)
 {
@@ -975,7 +1013,7 @@ static int acquire_resource(
      * moment since they are small, but if they need to grow in future
      * use-cases then per-CPU arrays or heap allocations may be required.
      */
-    xen_pfn_t mfn_list[2];
+    xen_pfn_t mfn_list[32];
     int rc;
 
     if ( copy_from_guest(&xmar, arg, 1) )
@@ -1010,6 +1048,11 @@ static int acquire_resource(
 
     switch ( xmar.type )
     {
+    case XENMEM_resource_grant_table:
+        rc = acquire_grant_table(d, xmar.id, xmar.frame, xmar.nr_frames,
+                                 mfn_list);
+        break;
+
     default:
         rc = arch_acquire_resource(d, xmar.type, xmar.id, xmar.frame,
                                    xmar.nr_frames, mfn_list);
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 838f248a59..d4ed8ba889 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -611,14 +611,20 @@ struct xen_mem_acquire_resource {
     uint16_t type;
 
 #define XENMEM_resource_ioreq_server 0
+#define XENMEM_resource_grant_table 1
 
     /*
      * IN - a type-specific resource identifier, which must be zero
      *      unless stated otherwise.
      *
      * type == XENMEM_resource_ioreq_server -> id == ioreq server id
+     * type == XENMEM_resource_grant_table -> id defined below
      */
     uint32_t id;
+
+#define XENMEM_resource_grant_table_id_grant 0
+#define XENMEM_resource_grant_table_id_status 1
+
     /* IN/OUT - As an IN parameter number of frames of the resource
      *          to be mapped. However, if the specified value is 0 and
      *          frame_list is NULL then this field will be set to the
diff --git a/xen/include/xen/grant_table.h b/xen/include/xen/grant_table.h
index b3a95fda58..e9125e43e7 100644
--- a/xen/include/xen/grant_table.h
+++ b/xen/include/xen/grant_table.h
@@ -55,6 +55,10 @@ int mem_sharing_gref_to_gfn(struct grant_table *gt, 
grant_ref_t ref,
 
 int gnttab_map_frame(struct domain *d, unsigned long idx, gfn_t gfn,
                      mfn_t *mfn);
+int gnttab_get_grant_frame(struct domain *d, unsigned long idx,
+                           mfn_t *mfn);
+int gnttab_get_status_frame(struct domain *d, unsigned long idx,
+                            mfn_t *mfn);
 
 unsigned int gnttab_dom0_frames(void);
 
-- 
2.11.0


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