[Xen-devel] [PATCH v2 3/4] xen/arm: introduce GNTTABOP_cache_flush

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Introduce a new hypercall to perform cache maintenance operation on
behalf of the guest. The argument is a machine address and a size. The
implementation checks that the memory range is owned by the guest or the
guest has been granted access to it by another domain.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

---

Changes in v2:
- do not check for mfn_to_page errors;
- take a reference to the page;
- replace printk with gdprintk;
- split long line;
- remove out label;
- move rcu_lock_current_domain down before the loop.
- move the hypercall to GNTTABOP;
- take a spin_lock before calling grant_map_exists.
---
 xen/common/grant_table.c         |   73 ++++++++++++++++++++++++++++++++++++++
 xen/include/public/grant_table.h |   19 ++++++++++
 2 files changed, 92 insertions(+)

diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 7a6399b..d5bb4f7 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -2641,6 +2641,79 @@ do_grant_table_op(
         }
         break;
     }
+    case GNTTABOP_cache_flush:
+    {
+        struct gnttab_cache_flush cflush;
+        struct domain *d, *owner;
+        struct page_info *page;
+        uint64_t mfn;
+        void *v;
+
+        /* currently unimplemented */
+        if ( count != 1 )
+            return -ENOSYS;
+
+        if ( copy_from_guest(&cflush, uop, 1) )
+            return -EFAULT;
+
+        if ( cflush.offset + cflush.size > PAGE_SIZE )
+            return -EINVAL;
+
+        if ( cflush.size == 0 || cflush.op == 0 )
+            return 0;
+
+        if ( cflush.op & ~(GNTTAB_CACHE_INVAL|GNTTAB_CACHE_CLEAN) )
+            return -EINVAL;
+
+        /* currently unimplemented */
+        if ( cflush.a.ref != 0 )
+            return -ENOSYS;
+
+        d = rcu_lock_current_domain();
+        if ( d == NULL )
+            return -ESRCH;
+
+        mfn = cflush.a.dev_bus_addr >> PAGE_SHIFT;
+
+        if ( !mfn_valid(mfn) )
+        {
+            gdprintk(XENLOG_G_ERR, "mfn=%llx is not valid\n", mfn);
+            rcu_unlock_domain(d);
+            return -EINVAL;
+        }
+
+        page = mfn_to_page(mfn);
+        owner = page_get_owner_and_reference(page);
+        if ( !owner )
+        {
+            rcu_unlock_domain(d);
+            return -EFAULT;
+        }
+
+        spin_lock(&owner->grant_table->lock);
+
+        if ( !grant_map_exists(d, owner->grant_table, mfn) )
+        {
+            spin_unlock(&owner->grant_table->lock);
+            put_page(page);
+            rcu_unlock_domain(d);
+            gdprintk(XENLOG_G_ERR, "mfn %llx hasn't been granted by %d to 
%d\n",
+                    mfn, owner->domain_id, d->domain_id);
+            return -EINVAL;
+        }
+
+        v = map_domain_page(mfn);
+        v += cflush.offset;
+
+        if ( cflush.op & GNTTAB_CACHE_INVAL )
+            invalidate_xen_dcache_va_range(v, cflush.size);
+        if ( cflush.op & GNTTAB_CACHE_CLEAN )
+            clean_xen_dcache_va_range(v, cflush.size);
+
+        unmap_domain_page(v);
+        spin_unlock(&owner->grant_table->lock);
+        put_page(page);
+    }
     default:
         rc = -ENOSYS;
         break;
diff --git a/xen/include/public/grant_table.h b/xen/include/public/grant_table.h
index b8a3d6c..1833bba 100644
--- a/xen/include/public/grant_table.h
+++ b/xen/include/public/grant_table.h
@@ -309,6 +309,7 @@ typedef uint16_t grant_status_t;
 #define GNTTABOP_get_status_frames    9
 #define GNTTABOP_get_version          10
 #define GNTTABOP_swap_grant_ref              11
+#define GNTTABOP_cache_flush         12
 #endif /* __XEN_INTERFACE_VERSION__ */
 /* ` } */
 
@@ -574,6 +575,24 @@ struct gnttab_swap_grant_ref {
 typedef struct gnttab_swap_grant_ref gnttab_swap_grant_ref_t;
 DEFINE_XEN_GUEST_HANDLE(gnttab_swap_grant_ref_t);
 
+/*
+ * Issue one or more cache maintenance operations on a portion of a
+ * page granted to the calling domain by a foreign domain.
+ */
+struct gnttab_cache_flush {
+    union {
+        uint64_t dev_bus_addr;
+        grant_ref_t ref;
+    } a;
+    uint32_t offset; /* offset from start of grant */
+    uint32_t size;   /* size within the grant */
+#define GNTTAB_CACHE_CLEAN      (1<<0)
+#define GNTTAB_CACHE_INVAL      (1<<1)
+    uint32_t op;
+};
+typedef struct gnttab_cache_flush gnttab_cache_flush_t;
+DEFINE_XEN_GUEST_HANDLE(gnttab_cache_flush_t);
+
 #endif /* __XEN_INTERFACE_VERSION__ */
 
 /*
-- 
1.7.10.4


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