[Xen-changelog] [xen master] x86emul: add "unblock NMI" retire flag

[patchbot@xxxxxxx]

commit 75704266f987c11ed98cd0a26c52898ab358e95e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Apr 19 13:24:18 2017 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Apr 19 13:24:18 2017 +0200

    x86emul: add "unblock NMI" retire flag
    
    No matter that we emulate IRET for (guest) real mode only right now, we
    should get its effect on (virtual) NMI delivery right. Note that we can
    simply check the other retire flags also in the !OKAY case, as the
    insn emulator now guarantees them to only be set on OKAY.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    Release-acked-by: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/x86/hvm/emulate.c             | 13 +++++++------
 xen/arch/x86/x86_emulate/x86_emulate.c | 13 +++++++++++--
 xen/arch/x86/x86_emulate/x86_emulate.h |  1 +
 3 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 91e269f..612c1f9 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -1955,9 +1955,6 @@ static int _hvm_emulate_one(struct hvm_emulate_ctxt 
*hvmemul_ctxt,
         memcpy(vio->mmio_insn, hvmemul_ctxt->insn_buf, vio->mmio_insn_bytes);
     }
 
-    if ( rc != X86EMUL_OKAY )
-        return rc;
-
     if ( hvmemul_ctxt->ctxt.retire.singlestep )
         hvm_inject_hw_exception(TRAP_debug, X86_EVENT_NO_EC);
 
@@ -1966,15 +1963,19 @@ static int _hvm_emulate_one(struct hvm_emulate_ctxt 
*hvmemul_ctxt,
     /* MOV-SS instruction toggles MOV-SS shadow, else we just clear it. */
     if ( hvmemul_ctxt->ctxt.retire.mov_ss )
         new_intr_shadow ^= HVM_INTR_SHADOW_MOV_SS;
-    else
+    else if ( rc != X86EMUL_RETRY )
         new_intr_shadow &= ~HVM_INTR_SHADOW_MOV_SS;
 
     /* STI instruction toggles STI shadow, else we just clear it. */
     if ( hvmemul_ctxt->ctxt.retire.sti )
         new_intr_shadow ^= HVM_INTR_SHADOW_STI;
-    else
+    else if ( rc != X86EMUL_RETRY )
         new_intr_shadow &= ~HVM_INTR_SHADOW_STI;
 
+    /* IRET, if valid in the given context, clears NMI blocking. */
+    if ( hvmemul_ctxt->ctxt.retire.unblock_nmi )
+        new_intr_shadow &= ~HVM_INTR_SHADOW_NMI;
+
     if ( hvmemul_ctxt->intr_shadow != new_intr_shadow )
     {
         hvmemul_ctxt->intr_shadow = new_intr_shadow;
@@ -1987,7 +1988,7 @@ static int _hvm_emulate_one(struct hvm_emulate_ctxt 
*hvmemul_ctxt,
         hvm_hlt(regs->eflags);
     }
 
-    return X86EMUL_OKAY;
+    return rc;
 }
 
 int hvm_emulate_one(
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index c32fe2d..6f10761 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -4002,6 +4002,7 @@ x86_emulate(
         uint32_t mask = X86_EFLAGS_VIP | X86_EFLAGS_VIF | X86_EFLAGS_VM;
 
         fail_if(!in_realmode(ctxt, ops));
+        ctxt->retire.unblock_nmi = true;
         if ( (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes),
                               &eip, op_bytes, ctxt, ops)) ||
              (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes),
@@ -7918,9 +7919,17 @@ int x86_emulate_wrapper(
 
     rc = x86_emulate(ctxt, ops);
 
-    /* Retire flags should only be set for successful instruction emulation. */
+    /*
+     * Most retire flags should only be set for successful instruction
+     * emulation.
+     */
     if ( rc != X86EMUL_OKAY )
-        ASSERT(ctxt->retire.raw == 0);
+    {
+        typeof(ctxt->retire) retire = ctxt->retire;
+
+        retire.unblock_nmi = false;
+        ASSERT(!retire.raw);
+    }
 
     /* All cases returning X86EMUL_EXCEPTION should have fault semantics. */
     if ( rc == X86EMUL_EXCEPTION )
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index d9a252e..e5ec8a6 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -490,6 +490,7 @@ struct x86_emulate_ctxt
             bool hlt:1;          /* Instruction HLTed. */
             bool mov_ss:1;       /* Instruction sets MOV-SS irq shadow. */
             bool sti:1;          /* Instruction sets STI irq shadow. */
+            bool unblock_nmi:1;  /* Instruction clears NMI blocking. */
             bool singlestep:1;   /* Singlestepping was active. */
         };
     } retire;
--
generated by git-patchbot for /home/xen/git/xen.git#master

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