From: Jan Beulich <jbeul...@suse.com>
Before adding a new vCPU operation to register the secondary time area
by guest-physical address, add code to actually keep such areas up-to-
date.
Note that pages aren't marked dirty when written to (matching the
handling of space mapped by map_vcpu_info()), on the basis that the
registrations are lost anyway across migration (or would need re-
populating at the target for transparent migration). Plus the contents
of the areas in question have to be deemed volatile in the first place
(so saving a "most recent" value is pretty meaningless even for e.g.
snapshotting).
Signed-off-by: Jan Beulich <jbeul...@suse.com>
Reviewed-by: Roger Pau Monné <roger....@citrix.com>
---
xen/arch/x86/time.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index af40a9993c81..332d2d79aeae 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1566,12 +1566,34 @@ static void __update_vcpu_system_time(struct vcpu *v,
int force)
v->arch.pv.pending_system_time = _u;
}
+static void write_time_guest_area(struct vcpu_time_info *map,
+ const struct vcpu_time_info *src)
+{
+ /* 1. Update userspace version. */
+ write_atomic(&map->version, src->version);
+ smp_wmb();
+
+ /* 2. Update all other userspace fields. */
+ *map = *src;
+
+ /* 3. Update userspace version again. */
+ smp_wmb();
+ write_atomic(&map->version, version_update_end(src->version));
+}
+
bool update_secondary_system_time(struct vcpu *v,
struct vcpu_time_info *u)
{
XEN_GUEST_HANDLE(vcpu_time_info_t) user_u = v->arch.time_info_guest;
+ struct vcpu_time_info *map = v->arch.time_guest_area.map;
struct guest_memory_policy policy = { .nested_guest_mode = false };
+ if ( map )
+ {
+ write_time_guest_area(map, u);
+ return true;
+ }
+
if ( guest_handle_is_null(user_u) )
return true;
--
2.42.0
