[PATCH v2 05/26] KVM: x86 emulator: allow loading null SS in long mode

Avi Kivity
2012-06-27T15:19:47Z

Null SS is valid in long mode; allow loading it.

Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/x86/kvm/emulate.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index db95a55..fe4340f 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1324,8 +1324,14 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
goto load;
}

- /* NULL selector is not valid for TR, CS and SS */
- if ((seg == VCPU_SREG_CS || seg == VCPU_SREG_SS || seg == VCPU_SREG_TR)
+ rpl = selector & 3;
+ cpl = ctxt->ops->cpl(ctxt);
+
+ /* NULL selector is not valid for TR, CS and SS (except for long mode) */
+ if ((seg == VCPU_SREG_CS
+ || (seg == VCPU_SREG_SS
+ && (ctxt->mode != X86EMUL_MODE_PROT64 || rpl != cpl))
+ || seg == VCPU_SREG_TR)
&& null_selector)
goto exception;

@@ -1352,9 +1358,7 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
goto exception;
}

- rpl = selector & 3;
dpl = seg_desc.dpl;
- cpl = ctxt->ops->cpl(ctxt);

switch (seg) {
case VCPU_SREG_SS:
--
1.7.11