Hi,

On 16/08/2019 00:36, Stefano Stabellini wrote:
Don't allow reserved-memory regions to be remapped into any unprivileged
guests, until reserved-memory regions are properly supported in Xen. For
now, do not call iomem_permit_access on them, because giving
iomem_permit_access to dom0 means that the toolstack will be able to
assign the region to a domU.

Signed-off-by: Stefano Stabellini <stefa...@xilinx.com>
---

Changes in v6:
- compare against "/reserved-memory/"

Changes in v5:
- fix check condition
- use strnicmp
- return error
- improve commit message

Changes in v4:
- compare the parent name with reserved-memory
- use dt_node_cmp

Changes in v3:
- new patch
---
  xen/arch/arm/domain_build.c | 24 ++++++++++++++++--------
  1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 4c8404155a..673ffa453f 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1155,15 +1155,23 @@ static int __init map_range_to_domain(const struct 
dt_device_node *dev,
      bool need_mapping = !dt_device_for_passthrough(dev);
      int res;
- res = iomem_permit_access(d, paddr_to_pfn(addr),
-                              paddr_to_pfn(PAGE_ALIGN(addr + len - 1)));
-    if ( res )
+    /*
+     * Don't give iomem permissions for reserved-memory ranges to domUs

In upstream Xen, this is only called for Dom0. So what are you referring to?

+     * until reserved-memory support is complete.

But as I pointed out before reserved-memory support is not going to happen via iomem. This is an abuse of the interface.

+     */

A better comment would be:

"reserved-memory regions are RAM carved out for special purpose. They are not MMIO and therefore a domain should not be able to manage them via the IOMEM interface".

+    if ( strnicmp(dt_node_full_name(dev), "/reserved-memory/",
+         strlen("/reserved-memory/")) != 0 )
      {
-        printk(XENLOG_ERR "Unable to permit to dom%d access to"
-               " 0x%"PRIx64" - 0x%"PRIx64"\n",
-               d->domain_id,
-               addr & PAGE_MASK, PAGE_ALIGN(addr + len) - 1);
-        return res;
+        res = iomem_permit_access(d, paddr_to_pfn(addr),
+                paddr_to_pfn(PAGE_ALIGN(addr + len - 1)));
+        if ( res )
+        {
+            printk(XENLOG_ERR "Unable to permit to dom%d access to"
+                    " 0x%"PRIx64" - 0x%"PRIx64"\n",
+                    d->domain_id,
+                    addr & PAGE_MASK, PAGE_ALIGN(addr + len) - 1);
+            return res;
+        }
      }
if ( need_mapping )


Cheers,

--
Julien Grall

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