From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Mon, 30 Jul 2018 09:26:53 +0000 (+0200)
Subject: x86/vmx: Don't clobber %dr6 while debugging state is lazy
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~31
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=037fe82cf5fadf0f74c3da70560ee7592a8f2083;p=xen.git

x86/vmx: Don't clobber %dr6 while debugging state is lazy

c/s 4f36452b63 introduced a write to %dr6 in the #DB intercept case, but the
guests debug registers may be lazy at this point, at which point the guests
later attempt to read %dr6 will discard this value and use the older stale
value.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
master commit: 3cdac2805692c7accde2f405d81cc0be799aee48
master date: 2018-07-19 14:06:48 +0100
---

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 610c8d6eb9..7189820bfc 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3701,6 +3701,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
              */
             __vmread(EXIT_QUALIFICATION, &exit_qualification);
             HVMTRACE_1D(TRAP_DEBUG, exit_qualification);
+            __restore_debug_registers(v);
             write_debugreg(6, exit_qualification | DR_STATUS_RESERVED_ONE);
             if ( !v->domain->debugger_attached )
             {