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List: xen-cvs
Subject: [Xen-changelog] [xen master] Restore HVM_OP hypercall continuation (partial revert of ae20ccf)
From: patchbot () xen ! org
Date: 2017-05-27 17:33:02
Message-ID: E1dEfaI-0003S8-Hh () xenbits ! xenproject ! org
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commit 7cc806d7f1d91dd4c4656f11226f043c749eb0ed
Author: George Dunlap <george.dunlap@citrix.com>
AuthorDate: Mon May 22 11:38:31 2017 +0100
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Wed May 24 17:15:34 2017 +0100
Restore HVM_OP hypercall continuation (partial revert of ae20ccf)
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 false. 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.
Reported-by: Xudong Hao <xudong.hao@intel.com>
Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Julien Grall <julien.grall@arm.com>
Tested-by: Xudong Hao <xudong.hao@intel.com>
---
xen/arch/x86/hvm/hvm.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 81691e2..273bcff 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;
}
--
generated by git-patchbot for /home/xen/git/xen.git#master
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