File 585bd5fe-x86-emul-correct-VMFUNC-return-value-h... of Package xen.4216

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File 585bd5fe-x86-emul-correct-VMFUNC-return-value-handling.patch of Package xen.4216

# Commit 3ab1876504d409689824e161a8b04e57e1e5dd46
# Date 2016-12-22 13:32:46 +0000
# Author Andrew Cooper <andrew.cooper3@citrix.com>
# Committer Andrew Cooper <andrew.cooper3@citrix.com>
x86/emul: Correct the return value handling of VMFUNC

The bracketing of x86_emulate() calling the ops->vmfunc() hook is wrong with
respect to the assignment to rc, which can trip the new assertions in
x86_emulate_wrapper().

The hvmemul_vmfunc() hook should only raise #UD if X86EMUL_EXCEPTION is
returned.  This is only a latent bug at the moment.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -1646,7 +1646,7 @@ static int hvmemul_vmfunc(
     if ( !hvm_funcs.altp2m_vcpu_emulate_vmfunc )
         return X86EMUL_UNHANDLEABLE;
     rc = hvm_funcs.altp2m_vcpu_emulate_vmfunc(ctxt->regs);
-    if ( rc != X86EMUL_OKAY )
+    if ( rc == X86EMUL_EXCEPTION )
         hvmemul_inject_hw_exception(TRAP_invalid_op, HVM_DELIVER_NO_ERROR_CODE,
                                     ctxt);
 
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -3981,7 +3981,7 @@ x86_emulate(
             generate_exception_if(lock_prefix | rep_prefix() | (vex.pfx == vex_66),
                                   EXC_UD, -1);
             fail_if(ops->vmfunc == NULL);
-            if ( (rc = ops->vmfunc(ctxt) != X86EMUL_OKAY) )
+            if ( (rc = ops->vmfunc(ctxt)) != X86EMUL_OKAY )
                 goto done;
             goto no_writeback;
 	case 0xfc: /* clzero */ {

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File 585bd5fe-x86-emul-correct-VMFUNC-return-value-handling.patch of Package xen.4216

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