x86/monitor: Notify monitor if an emulation fails.

If case of a vm_event with the emulate_flags set, if the instruction
is not implemented by the emulator, the monitor should be notified instead
of directly injecting a hw exception.
This behavior can be used to re-execute an instruction not supported by
the emulator using the real processor (e.g. altp2m) instead of just
crashing.

Signed-off-by: Petre Pircalabu <ppircalabu@bitdefender.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 182367e7f4a1f6d9995fd85c1419bbb6eee1c260..b970905a0b4fd652f55f838327b59bc9143f8786 100644 (file)
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2041,6 +2041,8 @@ int xc_monitor_debug_exceptions(xc_interface *xch, domid_t domain_id,
 int xc_monitor_cpuid(xc_interface *xch, domid_t domain_id, bool enable);
 int xc_monitor_privileged_call(xc_interface *xch, domid_t domain_id,
                                bool enable);
+int xc_monitor_emul_unimplemented(xc_interface *xch, domid_t domain_id,
+                                  bool enable);
 /**
  * This function enables / disables emulation for each REP for a
  * REP-compatible instruction.

diff --git a/tools/libxc/xc_monitor.c b/tools/libxc/xc_monitor.c
index a67782009d2a5ac3efb75eb8ac16c424fa40827b..604668015ec8257f7ba8b02fd86dd4546173207e 100644 (file)
--- a/tools/libxc/xc_monitor.c
+++ b/tools/libxc/xc_monitor.c
@@ -217,6 +217,20 @@ int xc_monitor_privileged_call(xc_interface *xch, domid_t domain_id,
     return do_domctl(xch, &domctl);
 }
 
+int xc_monitor_emul_unimplemented(xc_interface *xch, domid_t domain_id,
+                                  bool enable)
+{
+    DECLARE_DOMCTL;
+
+    domctl.cmd = XEN_DOMCTL_monitor_op;
+    domctl.domain = domain_id;
+    domctl.u.monitor_op.op = enable ? XEN_DOMCTL_MONITOR_OP_ENABLE
+                                    : XEN_DOMCTL_MONITOR_OP_DISABLE;
+    domctl.u.monitor_op.event = XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED;
+
+    return do_domctl(xch, &domctl);
+}
+
 /*
  * Local variables:
  * mode: C

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 4fe61b491d2750d07d131b5770d9342274a06462..19e7035078634b99a9c2673a9438852c6637f03d 100644 (file)
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -14,12 +14,14 @@
 #include <xen/sched.h>
 #include <xen/paging.h>
 #include <xen/trace.h>
+#include <xen/vm_event.h>
 #include <asm/event.h>
 #include <asm/i387.h>
 #include <asm/xstate.h>
 #include <asm/hvm/emulate.h>
 #include <asm/hvm/hvm.h>
 #include <asm/hvm/ioreq.h>
+#include <asm/hvm/monitor.h>
 #include <asm/hvm/trace.h>
 #include <asm/hvm/support.h>
 #include <asm/hvm/svm/svm.h>
@@ -2114,6 +2116,9 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, unsigned int trapnr,
          */
         return;
     case X86EMUL_UNIMPLEMENTED:
+        if ( hvm_monitor_emul_unimplemented() )
+            return;
+        /* fall-through */
     case X86EMUL_UNHANDLEABLE:
         hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx, rc);
         hvm_inject_hw_exception(trapnr, errcode);

diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
index 2787dfa7591a8c23d2cbb884f02210e25bb47413..4ce778c539f3485196fc83b86c358e10d09e10c5 100644 (file)
--- a/xen/arch/x86/hvm/monitor.c
+++ b/xen/arch/x86/hvm/monitor.c
@@ -57,6 +57,23 @@ bool hvm_monitor_cr(unsigned int index, unsigned long value, unsigned long old)
     return 0;
 }
 
+bool hvm_monitor_emul_unimplemented(void)
+{
+    struct vcpu *curr = current;
+
+    /*
+     * Send a vm_event to the monitor to signal that the current
+     * instruction couldn't be emulated.
+     */
+    vm_event_request_t req = {
+        .reason = VM_EVENT_REASON_EMUL_UNIMPLEMENTED,
+        .vcpu_id  = curr->vcpu_id,
+    };
+
+    return curr->domain->arch.monitor.emul_unimplemented_enabled &&
+        monitor_traps(curr, true, &req) == 1;
+}
+
 void hvm_monitor_msr(unsigned int msr, uint64_t value)
 {
     struct vcpu *curr = current;

diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
index 706454f23c5e166fbdf3f7cdc737dd6bbca6cdaa..e59f1f5e32fd83eeea0aceab1080cd4689a3c14f 100644 (file)
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -283,6 +283,19 @@ int arch_monitor_domctl_event(struct domain *d,
         break;
     }
 
+    case XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED:
+    {
+        bool old_status = ad->monitor.emul_unimplemented_enabled;
+
+        if ( unlikely(old_status == requested_status) )
+            return -EEXIST;
+
+        domain_pause(d);
+        ad->monitor.emul_unimplemented_enabled = requested_status;
+        domain_unpause(d);
+        break;
+    }
+
     default:
         /*
          * Should not be reached unless arch_monitor_get_capabilities() is

diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index 57da0fc0b6b9c3eb8de77f23f5efe8ef45ac9372..ee3f42d1bad82cf8ce12b5601eae6e71c09007bc 100644 (file)
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -407,6 +407,7 @@ struct arch_domain
         unsigned int cpuid_enabled                                         : 1;
         unsigned int descriptor_access_enabled                             : 1;
         unsigned int guest_request_userspace_enabled                       : 1;
+        unsigned int emul_unimplemented_enabled                            : 1;
         struct monitor_msr_bitmap *msr_bitmap;
         uint64_t write_ctrlreg_mask[4];
     } monitor;

diff --git a/xen/include/asm-x86/hvm/monitor.h b/xen/include/asm-x86/hvm/monitor.h
index cfd6661016d158e8517de3d919b0376f0dddcd37..6e22091f7bd4ddcc7b8d48048bf3e2353d90ae94 100644 (file)
--- a/xen/include/asm-x86/hvm/monitor.h
+++ b/xen/include/asm-x86/hvm/monitor.h
@@ -47,6 +47,7 @@ int hvm_monitor_cpuid(unsigned long insn_length, unsigned int leaf,
                       unsigned int subleaf);
 void hvm_monitor_interrupt(unsigned int vector, unsigned int type,
                            unsigned int err, uint64_t cr2);
+bool hvm_monitor_emul_unimplemented(void);
 
 #endif /* __ASM_X86_HVM_MONITOR_H__ */
 

diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index 765d0b41d21feb366c75e717859206693b14a251..0ada970e4f4bfbd65833033947dac5ef62f60f2a 100644 (file)
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -83,7 +83,8 @@ static inline uint32_t arch_monitor_get_capabilities(struct domain *d)
                    (1U << XEN_DOMCTL_MONITOR_EVENT_GUEST_REQUEST) |
                    (1U << XEN_DOMCTL_MONITOR_EVENT_DEBUG_EXCEPTION) |
                    (1U << XEN_DOMCTL_MONITOR_EVENT_CPUID) |
-                   (1U << XEN_DOMCTL_MONITOR_EVENT_INTERRUPT);
+                   (1U << XEN_DOMCTL_MONITOR_EVENT_INTERRUPT) |
+                   (1U << XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED);
 
     /* Since we know this is on VMX, we can just call the hvm func */
     if ( hvm_is_singlestep_supported() )

diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 36f93e887bbb72a595aedd5f37cf285d24ff3117..a6448ea80e871e0122a89bfbf7fc0801e0597a1d 100644 (file)
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1008,6 +1008,7 @@ struct xen_domctl_psr_cmt_op {
 #define XEN_DOMCTL_MONITOR_EVENT_PRIVILEGED_CALL       7
 #define XEN_DOMCTL_MONITOR_EVENT_INTERRUPT             8
 #define XEN_DOMCTL_MONITOR_EVENT_DESC_ACCESS           9
+#define XEN_DOMCTL_MONITOR_EVENT_EMUL_UNIMPLEMENTED    10
 
 struct xen_domctl_monitor_op {
     uint32_t op; /* XEN_DOMCTL_MONITOR_OP_* */

diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
index f01e47159d3d821283bb211cefb0c4cb9d699840..b531f71596de652dd7d8b68e7b5135e427113bd1 100644 (file)
--- a/xen/include/public/vm_event.h
+++ b/xen/include/public/vm_event.h
@@ -148,6 +148,8 @@
 #define VM_EVENT_REASON_INTERRUPT               12
 /* A descriptor table register was accessed. */
 #define VM_EVENT_REASON_DESCRIPTOR_ACCESS       13
+/* Current instruction is not implemented by the emulator */
+#define VM_EVENT_REASON_EMUL_UNIMPLEMENTED      14
 
 /* Supported values for the vm_event_write_ctrlreg index. */
 #define VM_EVENT_X86_CR0    0