[Xen-changelog] [xen stable-4.7] hvm/fep: Allow testing of instructions crossing the -1 -> 0 virtual boundary

[patchbot@xxxxxxx]

commit f515565bbae89bda4a1e1c11177fa0e4b32d4776
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Sep 12 15:55:48 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 12 15:55:48 2016 +0200

    hvm/fep: Allow testing of instructions crossing the -1 -> 0 virtual boundary
    
    The Force Emulation Prefix is named to follow its PV counterpart for cpuid 
or
    rdtsc, but isn't really an instruction prefix.  It behaves as a break-out 
into
    Xen, with the purpose of emulating the next instruction in the current 
state.
    
    It is important to be able to test legal situations which occur in real
    hardware, including instruction which cross certain boundaries, and
    instructions starting at 0.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 7b5cee79dad24e7006059667b02bd7de685d8ee5
    master date: 2016-09-08 16:39:46 +0100
---
 xen/arch/x86/hvm/hvm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 17fb210..40665f5 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3905,6 +3905,10 @@ void hvm_ud_intercept(struct cpu_user_regs *regs)
         {
             regs->eip += sizeof(sig);
             regs->eflags &= ~X86_EFLAGS_RF;
+
+            /* Zero the upper 32 bits of %rip if not in long mode. */
+            if ( !(hvm_long_mode_enabled(cur) && cs.attr.fields.l) )
+                regs->eip = regs->_eip;
         }
     }
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.7

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