[PATCH v4 10/16] libs/guest: add xg_foreignmemory_copy_{from,to}

[Frediano Ziglio <freddy77@xxxxxxxxx>]

From: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>

This change prepare code to use a new "foreign copy" hypercall.
The new hypercall will copy memory from/to a foreign domain.
The new hypercall can be emulated with a sequence of:
- map foreign memory;
- copy memory;
- unmap foreign memory.

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
---
 tools/libs/guest/xg_sr_common.c | 60 +++++++++++++++++++++++++++++++++
 tools/libs/guest/xg_sr_common.h |  8 +++++
 2 files changed, 68 insertions(+)

diff --git a/tools/libs/guest/xg_sr_common.c b/tools/libs/guest/xg_sr_common.c
index 86c148c62f..a94e9dfbff 100644
--- a/tools/libs/guest/xg_sr_common.c
+++ b/tools/libs/guest/xg_sr_common.c
@@ -156,6 +156,66 @@ static void __attribute__((unused)) build_assertions(void)
     BUILD_BUG_ON(sizeof(struct xc_sr_rec_hvm_params)        != 8);
 }
 
+enum {
+    foreigncopy_from,
+    foreigncopy_to
+};
+
+static int xg_foreignmemory_copy(xc_interface *xch, domid_t domid,
+                                 int dir, size_t nr_pages, void *buffer,
+                                 const xen_pfn_t foreign_pfns[nr_pages])
+{
+    if ( nr_pages == 0 )
+        return 0;
+
+    if ( !buffer || !foreign_pfns )
+    {
+        errno = EINVAL;
+        return -1;
+    }
+
+    int err[nr_pages];
+    const int prot = (dir == foreigncopy_from) ? PROT_READ : 
PROT_READ|PROT_WRITE;
+
+    void *p = xenforeignmemory_map(xch->fmem, domid, prot, nr_pages, 
foreign_pfns, err);
+    if ( !p )
+    {
+        errno = EINVAL;
+        return -1;
+    }
+
+    for ( size_t n = 0; n < nr_pages; ++n )
+        if ( err[n] )
+        {
+            xenforeignmemory_unmap(xch->fmem, p, nr_pages);
+            errno = -err[n];
+            return -1;
+        }
+
+    if ( dir == foreigncopy_from )
+        memcpy(buffer, p, nr_pages * XC_PAGE_SIZE);
+    else
+        memcpy(p, buffer, nr_pages * XC_PAGE_SIZE);
+
+    return xenforeignmemory_unmap(xch->fmem, p, nr_pages);
+}
+
+int xg_foreignmemory_copy_from(xc_interface *xch, domid_t dom,
+                               size_t nr_pages, void *dest,
+                               const xen_pfn_t source[nr_pages])
+{
+    return xg_foreignmemory_copy(xch, dom, foreigncopy_from,
+                                 nr_pages, dest, source);
+}
+
+int xg_foreignmemory_copy_to(xc_interface *xch, domid_t dom,
+                             size_t nr_pages, const xen_pfn_t dest[nr_pages],
+                             const void *source)
+{
+    return xg_foreignmemory_copy(xch, dom, foreigncopy_to,
+                                 nr_pages, (void *) source, dest);
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/tools/libs/guest/xg_sr_common.h b/tools/libs/guest/xg_sr_common.h
index e8452746e4..72c9511f38 100644
--- a/tools/libs/guest/xg_sr_common.h
+++ b/tools/libs/guest/xg_sr_common.h
@@ -553,6 +553,14 @@ static inline bool page_type_has_stream_data(uint32_t type)
     }
 }
 
+int xg_foreignmemory_copy_from(xc_interface *xch, domid_t dom,
+                               size_t nr_pages, void *dest,
+                               const xen_pfn_t source[nr_pages]);
+
+int xg_foreignmemory_copy_to(xc_interface *xch, domid_t dom,
+                             size_t nr_pages, const xen_pfn_t dest[nr_pages],
+                             const void *source);
+
 #endif
 /*
  * Local variables:
-- 
2.54.0