[xen staging] libxc: make xc_domain_maximum_gpfn() endianness-agnostic

[patchbot@xxxxxxx]

commit 190facdf877c8fc298dafa584f69e7aff8606c35
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jun 24 16:40:57 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jun 24 16:40:57 2021 +0200

    libxc: make xc_domain_maximum_gpfn() endianness-agnostic
    
    libxc generally uses uint32_t to represent domain IDs. This is fine as
    long as addresses of such variables aren't taken, to then pass into
    hypercalls: To the hypervisor, a domain ID is a 16-bit value. Introduce
    a wrapper struct to deal with the issue. (On architectures with
    arguments passed in registers, an intermediate variable would have been
    created by the compiler already anyway, just one of the wrong type.)
    
    The public interface change is both source and binary compatible for
    the architectures we currently support.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 tools/libs/ctrl/xc_domain.c |  3 ++-
 xen/common/memory.c         |  9 ++++++---
 xen/include/public/memory.h | 11 +++++++++--
 3 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/tools/libs/ctrl/xc_domain.c b/tools/libs/ctrl/xc_domain.c
index 7d118848f1..3803871538 100644
--- a/tools/libs/ctrl/xc_domain.c
+++ b/tools/libs/ctrl/xc_domain.c
@@ -856,7 +856,8 @@ int xc_domain_get_tsc_info(xc_interface *xch,
 
 int xc_domain_maximum_gpfn(xc_interface *xch, uint32_t domid, xen_pfn_t *gpfns)
 {
-    long rc = do_memory_op(xch, XENMEM_maximum_gpfn, &domid, sizeof(domid));
+    struct xen_memory_domain dom = { .domid = domid };
+    long rc = do_memory_op(xch, XENMEM_maximum_gpfn, &dom, sizeof(dom));
 
     if ( rc >= 0 )
     {
diff --git a/xen/common/memory.c b/xen/common/memory.c
index 72a6b70cb5..ba212f971c 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -1351,7 +1351,6 @@ long do_memory_op(unsigned long cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
     long rc;
     struct xen_memory_reservation reservation;
     struct memop_args args;
-    domid_t domid;
     unsigned long start_extent = cmd >> MEMOP_EXTENT_SHIFT;
     int op = cmd & MEMOP_CMD_MASK;
 
@@ -1452,13 +1451,16 @@ long do_memory_op(unsigned long cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
     case XENMEM_current_reservation:
     case XENMEM_maximum_reservation:
     case XENMEM_maximum_gpfn:
+    {
+        struct xen_memory_domain domain;
+
         if ( unlikely(start_extent) )
             return -EINVAL;
 
-        if ( copy_from_guest(&domid, arg, 1) )
+        if ( copy_from_guest(&domain, arg, 1) )
             return -EFAULT;
 
-        d = rcu_lock_domain_by_any_id(domid);
+        d = rcu_lock_domain_by_any_id(domain.domid);
         if ( d == NULL )
             return -ESRCH;
 
@@ -1486,6 +1488,7 @@ long do_memory_op(unsigned long cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg)
         rcu_unlock_domain(d);
 
         break;
+    }
 
     case XENMEM_add_to_physmap:
     {
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 50e73eef98..383a9468c3 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -148,16 +148,23 @@ DEFINE_XEN_GUEST_HANDLE(xen_memory_exchange_t);
  */
 #define XENMEM_maximum_ram_page     2
 
+struct xen_memory_domain {
+    /* [IN] Domain information is being queried for. */
+    domid_t domid;
+};
+
 /*
  * Returns the current or maximum memory reservation, in pages, of the
  * specified domain (may be DOMID_SELF). Returns -ve errcode on failure.
- * arg == addr of domid_t.
+ * arg == addr of struct xen_memory_domain.
  */
 #define XENMEM_current_reservation  3
 #define XENMEM_maximum_reservation  4
 
 /*
- * Returns the maximum GPFN in use by the guest, or -ve errcode on failure.
+ * Returns the maximum GFN in use by the specified domain (may be DOMID_SELF).
+ * Returns -ve errcode on failure.
+ * arg == addr of struct xen_memory_domain.
  */
 #define XENMEM_maximum_gpfn         14
 
--
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