[Xen-devel] [PATCH v2 03/10] xen: extend XEN_DOMCTL_memory_mapping to handle memory policy

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Reuse the existing padding field to pass memory policy information.  On
Arm, the caller can specify whether the memory should be mapped as
device nGRE, which is the default and the only possibility today, or
cacheable memory write-back. On x86, the only option is uncachable. The
current behavior becomes the default (numerically '0').

On ARM, map device nGRE as p2m_mmio_direct_dev (as it is already done
today) and WB cacheable memory as p2m_mmio_direct_c.

On x86, return error if the memory policy requested is not
MEMORY_POLICY_X86_UC.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
CC: JBeulich@xxxxxxxx
CC: andrew.cooper3@xxxxxxxxxx

---
Changes in v2:
- rebase
- use p2m_mmio_direct_c
- use EOPNOTSUPP
- rename cache_policy to memory policy
- rename MEMORY_POLICY_DEVMEM to MEMORY_POLICY_ARM_DEV_nGRE
- rename MEMORY_POLICY_MEMORY to MEMORY_POLICY_ARM_MEM_WB
- add MEMORY_POLICY_X86_UC
- add MEMORY_POLICY_DEFAULT and use it
---
 xen/common/domctl.c         | 23 +++++++++++++++++++++--
 xen/include/public/domctl.h | 14 +++++++++++++-
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index 140f979..9f62ead 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -928,6 +928,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         unsigned long mfn_end = mfn + nr_mfns - 1;
         int add = op->u.memory_mapping.add_mapping;
         p2m_type_t p2mt;
+        uint32_t memory_policy = op->u.memory_mapping.memory_policy;
 
         ret = -EINVAL;
         if ( mfn_end < mfn || /* wrap? */
@@ -958,9 +959,27 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) 
u_domctl)
         if ( add )
         {
             printk(XENLOG_G_DEBUG
-                   "memory_map:add: dom%d gfn=%lx mfn=%lx nr=%lx\n",
-                   d->domain_id, gfn, mfn, nr_mfns);
+                   "memory_map:add: dom%d gfn=%lx mfn=%lx nr=%lx cache=%u\n",
+                   d->domain_id, gfn, mfn, nr_mfns, memory_policy);
 
+            switch ( memory_policy )
+            {
+#ifdef CONFIG_ARM
+                case MEMORY_POLICY_ARM_MEM_WB:
+                    p2mt = p2m_mmio_direct_c;
+                    break;
+                case MEMORY_POLICY_ARM_DEV_nGRE:
+                    p2mt = p2m_mmio_direct_dev;
+                    break;
+#endif
+#ifdef CONFIG_X86
+                case MEMORY_POLICY_X86_UC:
+                    p2mt = p2m_mmio_direct;
+                    break;
+#endif
+                default:
+                    return -EOPNOTSUPP;
+            }
             ret = map_regions(d, _gfn(gfn), nr_mfns, _mfn(mfn), p2mt);
             if ( ret < 0 )
                 printk(XENLOG_G_WARNING
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 19486d5..9330387 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -571,12 +571,24 @@ struct xen_domctl_bind_pt_irq {
 */
 #define DPCI_ADD_MAPPING         1
 #define DPCI_REMOVE_MAPPING      0
+/*
+ * Default memory policy. Corresponds to:
+ * Arm: MEMORY_POLICY_ARM_DEV_nGRE
+ * x86: MEMORY_POLICY_X86_UC
+ */
+#define MEMORY_POLICY_DEFAULT    0
+/* x86 only. Memory type UNCACHABLE */
+#define MEMORY_POLICY_X86_UC     0
+/* Arm only. Outer Shareable, Device-nGRE memory */
+#define MEMORY_POLICY_ARM_DEV_nGRE       0
+/* Arm only. Outer Shareable, Outer/Inner Write-Back Cacheable memory */
+#define MEMORY_POLICY_ARM_MEM_WB         1
 struct xen_domctl_memory_mapping {
     uint64_aligned_t first_gfn; /* first page (hvm guest phys page) in range */
     uint64_aligned_t first_mfn; /* first page (machine page) in range */
     uint64_aligned_t nr_mfns;   /* number of pages in range (>0) */
     uint32_t add_mapping;       /* add or remove mapping */
-    uint32_t padding;           /* padding for 64-bit aligned structure */
+    uint32_t memory_policy;      /* cacheability of the memory mapping */
 };
 
 
-- 
1.9.1


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