Commit ae20ccf removed the hypercall continuation logic from the end
of do_hvm_op(), claiming:
"This patch removes the need for handling HVMOP restarts, so that
infrastructure is removed."
That turns out to be only half true. The removal of
HVMOP_set_mem_type removed the need to store a start iteration value
in the hypercall continuation, but a grep through hvm.c for ERESTART
turns up at least two places where do_hvm_op() may still need a
hypercall continuation:
* HVMOP_set_hvm_param can return -ERESTART when setting
HVM_PARAM_IDENT_PT in the event that it fails to acquire the domctl
lock
* HVMOP_flush_tlbs can return -ERESTART if several vcpus call it at
the same time
In both cases, a simple restart (with no stored iteration information)
is necessary.
Add a check for -ERESTART again, along with a comment at the top of
the function regarding the lack of decoding any information from the
op value.
Remove a stray blank line at the end of the file while we're here.
Reported-by: Xudong Hao <xudong....@intel.com>
Signed-off-by: George Dunlap <george.dun...@citrix.com>
---
CC: Andrew Cooper <andrew.coop...@citrix.com>
CC: Jan Beulich <jbeul...@suse.com>
CC: Paul Durrant <paul.durr...@citrix.com>
CC: Julien Grall <julien.gr...@arm.com>
---
xen/arch/x86/hvm/hvm.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 81691e2..e3e817d 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4544,6 +4544,13 @@ long do_hvm_op(unsigned long op,
XEN_GUEST_HANDLE_PARAM(void) arg)
{
long rc = 0;
+ /*
+ * NB: hvm_op can be part of a restarted hypercall; but at the
+ * moment the only hypercalls which do continuations don't need to
+ * store any iteration information (since they're just re-trying
+ * the acquisition of a lock).
+ */
+
switch ( op )
{
case HVMOP_set_evtchn_upcall_vector:
@@ -4636,6 +4643,10 @@ long do_hvm_op(unsigned long op,
XEN_GUEST_HANDLE_PARAM(void) arg)
}
}
+ if ( rc == -ERESTART )
+ rc = hypercall_create_continuation(__HYPERVISOR_hvm_op, "lh",
+ op, arg);
+
return rc;
}
@@ -4869,4 +4880,3 @@ void hvm_set_segment_register(struct vcpu *v, enum
x86_segment seg,
* indent-tabs-mode: nil
* End:
*/
-
--
2.1.4
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