[Xen-devel] [PATCH 2/2] x86/pv: Check that emulate_privileged_op() didn't change TF

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

As the comment says, the guest shouldn't be able to change X86_EFLAGS_TF,
although we don't care which value it currently has.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/arch/x86/traps.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index e45ff71..6dbdaa0 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -3395,7 +3395,8 @@ static int emulate_privileged_op(struct cpu_user_regs 
*regs)
      * Un-mirror virtualized state from EFLAGS.
      * Nothing we allow to be emulated can change TF, IF, or IOPL.
      */
-    ASSERT(!((regs->_eflags ^ eflags) & (X86_EFLAGS_IF | X86_EFLAGS_IOPL)));
+    ASSERT(!((regs->_eflags ^ eflags) &
+             (X86_EFLAGS_TF | X86_EFLAGS_IF | X86_EFLAGS_IOPL)));
     regs->_eflags |= X86_EFLAGS_IF;
     regs->_eflags &= ~X86_EFLAGS_IOPL;
 
-- 
2.1.4


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