KVM: x86: Push potential exception error code on task switches

When a fault triggers a task switch, the error code, if existent, has to
be pushed on the new task's stack. Implement the missing bits.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 18 insertions, 4 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index aace5659bbe0..585d0ef4a5f6 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2344,8 +2344,9 @@ static int task_switch_32(struct x86_emulate_ctxt *ctxt,
 }
 
 static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
-                                    struct x86_emulate_ops *ops,
-                                    u16 tss_selector, int reason)
+                                   struct x86_emulate_ops *ops,
+                                   u16 tss_selector, int reason,
+                                   bool has_error_code, u32 error_code)
 {
         struct desc_struct curr_tss_desc, next_tss_desc;
         int ret;
@@ -2418,12 +2419,22 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
         ops->set_cached_descriptor(&next_tss_desc, VCPU_SREG_TR, ctxt->vcpu);
         ops->set_segment_selector(tss_selector, VCPU_SREG_TR, ctxt->vcpu);
 
+        if (has_error_code) {
+                struct decode_cache *c = &ctxt->decode;
+
+                c->op_bytes = c->ad_bytes = (next_tss_desc.type & 8) ? 4 : 2;
+                c->lock_prefix = 0;
+                c->src.val = (unsigned long) error_code;
+                emulate_push(ctxt);
+        }
+
         return ret;
 }
 
 int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
                          struct x86_emulate_ops *ops,
-                         u16 tss_selector, int reason)
+                         u16 tss_selector, int reason,
+                         bool has_error_code, u32 error_code)
 {
         struct decode_cache *c = &ctxt->decode;
         int rc;
@@ -2431,12 +2442,15 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
         memset(c, 0, sizeof(struct decode_cache));
         c->eip = ctxt->eip;
         memcpy(c->regs, ctxt->vcpu->arch.regs, sizeof c->regs);
+        c->dst.type = OP_NONE;
 
-        rc = emulator_do_task_switch(ctxt, ops, tss_selector, reason);
+        rc = emulator_do_task_switch(ctxt, ops, tss_selector, reason,
+                                     has_error_code, error_code);
 
         if (rc == X86EMUL_CONTINUE) {
                 memcpy(ctxt->vcpu->arch.regs, c->regs, sizeof c->regs);
                 kvm_rip_write(ctxt->vcpu, c->eip);
+                rc = writeback(ctxt, ops);
         }
 
         return rc;