[PATCH v5 01/16] x86/hvm: make sure emulation is retried if domain is shutting down

[Paul Durrant <paul.durrant@citrix.com>]

The addition of commit 2df1aa01 "x86/hvm: remove hvm_io_pending() check
in hvmemul_do_io()" causes a problem in migration because I/O that was
caught by the test of vcpu_start_shutdown_deferral() in
hvm_send_assist_req() is now considered completed rather than requiring
a retry.

This patch fixes the problem by having hvm_send_assist_req() return
X86EMUL_RETRY rather than X86EMUL_OKAY if the
vcpu_start_shutdown_deferral() test fails and then making sure that
the emulation state is reset if the domain is found to be shutting
down.

Reported-by: Don Slutz <don.slutz@gmail.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Keir Fraser <keir@xen.org>
Jan Beulich <jbeulich@suse.com>
Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/hvm/emulate.c |    2 +-
 xen/arch/x86/hvm/hvm.c     |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index fe5661d..8b60843 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -183,7 +183,7 @@ static int hvmemul_do_io(
         else
         {
             rc = hvm_send_assist_req(s, &p);
-            if ( rc != X86EMUL_RETRY )
+            if ( rc != X86EMUL_RETRY || curr->domain->is_shutting_down )
                 vio->io_state = HVMIO_none;
             else if ( data_is_addr || dir == IOREQ_WRITE )
                 rc = X86EMUL_OKAY;
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 535d622..f0cf064 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2613,7 +2613,7 @@ int hvm_send_assist_req(struct hvm_ioreq_server *s, ioreq_t *proto_p)
 
     ASSERT(s);
     if ( unlikely(!vcpu_start_shutdown_deferral(curr)) )
-        return X86EMUL_OKAY;
+        return X86EMUL_RETRY;
 
     list_for_each_entry ( sv,
                           &s->ioreq_vcpu_list,
-- 
1.7.10.4