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[Xen-devel] [PATCH v2] x86/monitor: Notify monitor if an emulation fails.

  • To: xen-devel@xxxxxxxxxxxxx
  • From: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
  • Date: Tue, 11 Jul 2017 17:53:06 +0300
  • Cc: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>, wei.liu2@xxxxxxxxxx, tamas@xxxxxxxxxxxxx, ian.jackson@xxxxxxxxxxxxx, rcojocaru@xxxxxxxxxxxxxxx
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  • Delivery-date: Tue, 11 Jul 2017 14:53:18 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
If case of a vm_event with the emulate_flags set, if the instruction
cannot be emulated, 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@xxxxxxxxxxxxxxx>

---
Changed since v1:
  * Removed the emulation kind check when calling hvm_inject_hw_exception
---
 tools/libxc/include/xenctrl.h                      |   2 +
 tools/libxc/xc_monitor.c                           |  14 ++
 ...itor-Notify-monitor-if-an-emulation-fails.patch | 212 +++++++++++++++++++++
 xen/arch/x86/hvm/emulate.c                         |   5 +-
 xen/arch/x86/hvm/monitor.c                         |  19 ++
 xen/arch/x86/monitor.c                             |  12 ++
 xen/include/asm-x86/domain.h                       |   1 +
 xen/include/asm-x86/hvm/monitor.h                  |   1 +
 xen/include/asm-x86/monitor.h                      |   3 +-
 xen/include/public/domctl.h                        |   1 +
 xen/include/public/vm_event.h                      |   2 +
 11 files changed, 270 insertions(+), 2 deletions(-)
 create mode 100644 
tools/tests/xen-access/0001-x86-monitor-Notify-monitor-if-an-emulation-fails.patch

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index c51bb3b..8deb5ac 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2029,6 +2029,8 @@ 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_unhandleable(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 b44ce93..8e72c6c 100644
--- a/tools/libxc/xc_monitor.c
+++ b/tools/libxc/xc_monitor.c
@@ -216,6 +216,20 @@ int xc_monitor_privileged_call(xc_interface *xch, domid_t 
domain_id,
     return do_domctl(xch, &domctl);
 }
 
+int xc_monitor_emul_unhandleable(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_UNHANDLEABLE;
+
+    return do_domctl(xch, &domctl);
+}
+
 /*
  * Local variables:
  * mode: C
diff --git 
a/tools/tests/xen-access/0001-x86-monitor-Notify-monitor-if-an-emulation-fails.patch
 
b/tools/tests/xen-access/0001-x86-monitor-Notify-monitor-if-an-emulation-fails.patch
new file mode 100644
index 0000000..7a0d091
--- /dev/null
+++ 
b/tools/tests/xen-access/0001-x86-monitor-Notify-monitor-if-an-emulation-fails.patch
@@ -0,0 +1,212 @@
+From 97b3e9c22c7c6a0e49bde4e1bb6866a02ad43007 Mon Sep 17 00:00:00 2001
+From: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
+Date: Thu, 29 Jun 2017 20:40:46 +0300
+Subject: [PATCH] x86/monitor: Notify monitor if an emulation fails.
+
+If case of a vm_event with the emulate_flags set, if the instruction
+cannot be emulated, 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@xxxxxxxxxxxxxxx>
+---
+ tools/libxc/include/xenctrl.h     |  2 ++
+ tools/libxc/xc_monitor.c          | 14 ++++++++++++++
+ xen/arch/x86/hvm/emulate.c        |  5 ++++-
+ xen/arch/x86/hvm/monitor.c        | 19 +++++++++++++++++++
+ xen/arch/x86/monitor.c            | 12 ++++++++++++
+ xen/include/asm-x86/domain.h      |  1 +
+ xen/include/asm-x86/hvm/monitor.h |  1 +
+ xen/include/asm-x86/monitor.h     |  3 ++-
+ xen/include/public/domctl.h       |  1 +
+ xen/include/public/vm_event.h     |  2 ++
+ 10 files changed, 58 insertions(+), 2 deletions(-)
+
+diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
+index c51bb3b..8deb5ac 100644
+--- a/tools/libxc/include/xenctrl.h
++++ b/tools/libxc/include/xenctrl.h
+@@ -2029,6 +2029,8 @@ 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_unhandleable(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 b44ce93..8e72c6c 100644
+--- a/tools/libxc/xc_monitor.c
++++ b/tools/libxc/xc_monitor.c
+@@ -216,6 +216,20 @@ int xc_monitor_privileged_call(xc_interface *xch, domid_t 
domain_id,
+     return do_domctl(xch, &domctl);
+ }
+ 
++int xc_monitor_emul_unhandleable(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_UNHANDLEABLE;
++
++    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 e97aa69..083a38a 100644
+--- 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>
+@@ -2101,7 +2103,8 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, 
unsigned int trapnr,
+         return;
+     case X86EMUL_UNHANDLEABLE:
+         hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx);
+-        hvm_inject_hw_exception(trapnr, errcode);
++        if ( (kind != EMUL_KIND_NORMAL) || !hvm_monitor_emul_unhandleable() )
++            hvm_inject_hw_exception(trapnr, errcode);
+         break;
+     case X86EMUL_EXCEPTION:
+         hvm_inject_event(&ctx.ctxt.event);
+diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
+index a7ccfc4..02e0ba5 100644
+--- a/xen/arch/x86/hvm/monitor.c
++++ b/xen/arch/x86/hvm/monitor.c
+@@ -57,6 +57,25 @@ bool_t hvm_monitor_cr(unsigned int index, unsigned long 
value, unsigned long old
+     return 0;
+ }
+ 
++
++bool hvm_monitor_emul_unhandleable(void)
++{
++    struct vcpu *curr = current;
++    struct domain *d = curr->domain;
++
++    /*
++     * 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_UNHANDLEABLE,
++        .vcpu_id  = curr->vcpu_id,
++    };
++
++    return ( d->arch.monitor.emul_unhandleable &&
++             monitor_traps(curr, true, &req) );
++}
++
+ 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 706454f..51252fe 100644
+--- a/xen/arch/x86/monitor.c
++++ b/xen/arch/x86/monitor.c
+@@ -283,6 +283,18 @@ int arch_monitor_domctl_event(struct domain *d,
+         break;
+     }
+ 
++    case XEN_DOMCTL_MONITOR_EVENT_EMUL_UNHANDLEABLE:
++    {
++        bool old_status = ad->monitor.emul_unhandleable;
++        if ( unlikely(old_status == requested_status) )
++            return -EEXIST;
++
++        domain_pause(d);
++        ad->monitor.emul_unhandleable = 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 c10522b..7f3b54c 100644
+--- a/xen/include/asm-x86/domain.h
++++ b/xen/include/asm-x86/domain.h
+@@ -405,6 +405,7 @@ struct arch_domain
+         unsigned int debug_exception_sync        : 1;
+         unsigned int cpuid_enabled               : 1;
+         unsigned int descriptor_access_enabled   : 1;
++        unsigned int emul_unhandleable           : 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 d9efb35..4030be7 100644
+--- 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_unhandleable(void);
+ 
+ #endif /* __ASM_X86_HVM_MONITOR_H__ */
+ 
+diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
+index c5c323b..38ba0ff 100644
+--- a/xen/include/asm-x86/monitor.h
++++ b/xen/include/asm-x86/monitor.h
+@@ -77,7 +77,8 @@ 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_UNHANDLEABLE);
+ 
+     /* 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 ff39762..6bd8666 100644
+--- a/xen/include/public/domctl.h
++++ b/xen/include/public/domctl.h
+@@ -1083,6 +1083,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_domctl_psr_cmt_op_t);
+ #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_UNHANDLEABLE     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 f01e471..5548afb 100644
+--- 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 couldn't be emulated */
++#define VM_EVENT_REASON_EMUL_UNHANDLEABLE       14
+ 
+ /* Supported values for the vm_event_write_ctrlreg index. */
+ #define VM_EVENT_X86_CR0    0
+-- 
+2.7.4
+
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index e97aa69..f52aa87 100644
--- 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>
@@ -2101,7 +2103,8 @@ void hvm_emulate_one_vm_event(enum emul_kind kind, 
unsigned int trapnr,
         return;
     case X86EMUL_UNHANDLEABLE:
         hvm_dump_emulation_state(XENLOG_G_DEBUG, "Mem event", &ctx);
-        hvm_inject_hw_exception(trapnr, errcode);
+        if ( !hvm_monitor_emul_unhandleable() )
+            hvm_inject_hw_exception(trapnr, errcode);
         break;
     case X86EMUL_EXCEPTION:
         hvm_inject_event(&ctx.ctxt.event);
diff --git a/xen/arch/x86/hvm/monitor.c b/xen/arch/x86/hvm/monitor.c
index a7ccfc4..02e0ba5 100644
--- a/xen/arch/x86/hvm/monitor.c
+++ b/xen/arch/x86/hvm/monitor.c
@@ -57,6 +57,25 @@ bool_t hvm_monitor_cr(unsigned int index, unsigned long 
value, unsigned long old
     return 0;
 }
 
+
+bool hvm_monitor_emul_unhandleable(void)
+{
+    struct vcpu *curr = current;
+    struct domain *d = curr->domain;
+
+    /*
+     * 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_UNHANDLEABLE,
+        .vcpu_id  = curr->vcpu_id,
+    };
+
+    return ( d->arch.monitor.emul_unhandleable &&
+             monitor_traps(curr, true, &req) );
+}
+
 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 706454f..51252fe 100644
--- a/xen/arch/x86/monitor.c
+++ b/xen/arch/x86/monitor.c
@@ -283,6 +283,18 @@ int arch_monitor_domctl_event(struct domain *d,
         break;
     }
 
+    case XEN_DOMCTL_MONITOR_EVENT_EMUL_UNHANDLEABLE:
+    {
+        bool old_status = ad->monitor.emul_unhandleable;
+        if ( unlikely(old_status == requested_status) )
+            return -EEXIST;
+
+        domain_pause(d);
+        ad->monitor.emul_unhandleable = 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 c10522b..7f3b54c 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -405,6 +405,7 @@ struct arch_domain
         unsigned int debug_exception_sync        : 1;
         unsigned int cpuid_enabled               : 1;
         unsigned int descriptor_access_enabled   : 1;
+        unsigned int emul_unhandleable           : 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 d9efb35..4030be7 100644
--- 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_unhandleable(void);
 
 #endif /* __ASM_X86_HVM_MONITOR_H__ */
 
diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index c5c323b..38ba0ff 100644
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -77,7 +77,8 @@ 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_UNHANDLEABLE);
 
     /* 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 ff39762..6bd8666 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -1083,6 +1083,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_domctl_psr_cmt_op_t);
 #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_UNHANDLEABLE     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 f01e471..5548afb 100644
--- 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 couldn't be emulated */
+#define VM_EVENT_REASON_EMUL_UNHANDLEABLE       14
 
 /* Supported values for the vm_event_write_ctrlreg index. */
 #define VM_EVENT_X86_CR0    0
-- 
2.7.4


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