xen: make VMTRACE support optional

The VMTRACE feature is depends on Platform/Arch HW and code support and now
can be used only on x86 HVM with Intel VT-x (INTEL_VMX) enabled.
This makes VMTRACE support optional by introducing HVM Kconfig option:
- CONFIG_VMTRACE to enable/disable the feature.

Signed-off-by: Grygorii Strashko <grygorii_strashko@epam.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Tamas K Lengyel <tamas@tklengyel.com>

xen/arch/x86/domctl.c

@@ -154,6 +154,7 @@ void arch_get_domain_info(const struct domain *d,
 static int do_vmtrace_op(struct domain *d, struct xen_domctl_vmtrace_op *op,
                          XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
 {
+#ifdef CONFIG_VMTRACE
     struct vcpu *v;
     int rc;
 
@@ -198,6 +199,9 @@ static int do_vmtrace_op(struct domain *d, struct xen_domctl_vmtrace_op *op,
     vcpu_unpause(v);
 
     return rc;
+#else
+    return -EOPNOTSUPP;
+#endif
 }
 
 #define MAX_IOPORTS 0x10000

xen/arch/x86/hvm/Kconfig

@@ -34,6 +34,18 @@ config INTEL_VMX
 	  If your system includes a processor with Intel VT-x support, say Y.
 	  If in doubt, say Y.
 
+config VMTRACE
+	bool "HW VM tracing support"
+	depends on INTEL_VMX
+	default y
+	help
+	  Enables HW VM tracing support which allows to configure HW processor
+	  features (vmtrace_op) to enable capturing information about software
+	  execution using dedicated hardware facilities with minimal interference
+	  to the software being traced. The trace data can be retrieved using buffer
+	  shared between Xen and domain
+	  (see XENMEM_acquire_resource(XENMEM_resource_vmtrace_buf)).
+
 config HVM_FEP
 	bool "HVM Forced Emulation Prefix support (UNSUPPORTED)" if UNSUPPORTED
 	default DEBUG

xen/arch/x86/hvm/vmx/vmcs.c

@@ -306,6 +306,7 @@ static int vmx_init_vmcs_config(bool bsp)
 
     rdmsrl(MSR_IA32_VMX_MISC, _vmx_misc_cap);
 
+#ifdef CONFIG_VMTRACE
     /* Check whether IPT is supported in VMX operation. */
     if ( bsp )
         vmtrace_available = cpu_has_proc_trace &&
@@ -317,6 +318,7 @@ static int vmx_init_vmcs_config(bool bsp)
                smp_processor_id());
         return -EINVAL;
     }
+#endif
 
     if ( caps.cpu_based_exec_control & CPU_BASED_ACTIVATE_SECONDARY_CONTROLS )
     {

xen/arch/x86/hvm/vmx/vmx.c

@@ -622,6 +622,7 @@ static void cf_check domain_creation_finished(struct domain *d)
 
 static void vmx_init_ipt(struct vcpu *v)
 {
+#ifdef CONFIG_VMTRACE
     unsigned int size = v->domain->vmtrace_size;
 
     if ( !size )
@@ -632,6 +633,7 @@ static void vmx_init_ipt(struct vcpu *v)
     ASSERT(size >= PAGE_SIZE && (size & (size - 1)) == 0);
 
     v->arch.msrs->rtit.output_limit = size - 1;
+#endif
 }
 
 static int cf_check vmx_vcpu_initialise(struct vcpu *v)
@@ -723,11 +725,13 @@ static void vmx_save_guest_msrs(struct vcpu *v)
      */
     v->arch.hvm.vmx.shadow_gs = read_gs_shadow();
 
+#ifdef CONFIG_VMTRACE
     if ( v->arch.hvm.vmx.ipt_active )
     {
         rdmsrl(MSR_RTIT_OUTPUT_MASK, msrs->rtit.output_mask);
         rdmsrl(MSR_RTIT_STATUS, msrs->rtit.status);
     }
+#endif
 
     if ( cp->feat.pks )
         msrs->pkrs = rdpkrs_and_cache();
@@ -746,12 +750,14 @@ static void vmx_restore_guest_msrs(struct vcpu *v)
     if ( cpu_has_msr_tsc_aux )
         wrmsr_tsc_aux(msrs->tsc_aux);
 
+#ifdef CONFIG_VMTRACE
     if ( v->arch.hvm.vmx.ipt_active )
     {
         wrmsrl(MSR_RTIT_OUTPUT_BASE, page_to_maddr(v->vmtrace.pg));
         wrmsrl(MSR_RTIT_OUTPUT_MASK, msrs->rtit.output_mask);
         wrmsrl(MSR_RTIT_STATUS, msrs->rtit.status);
     }
+#endif
 
     if ( cp->feat.pks )
         wrpkrs(msrs->pkrs);
@@ -2629,6 +2635,7 @@ static bool cf_check vmx_get_pending_event(
     return true;
 }
 
+#ifdef CONFIG_VMTRACE
 /*
  * We only let vmtrace agents see and modify a subset of bits in MSR_RTIT_CTL.
  * These all pertain to data-emitted into the trace buffer(s).  Must not
@@ -2771,6 +2778,7 @@ static int cf_check vmtrace_reset(struct vcpu *v)
     v->arch.msrs->rtit.status = 0;
     return 0;
 }
+#endif
 
 static uint64_t cf_check vmx_get_reg(struct vcpu *v, unsigned int reg)
 {
@@ -2945,11 +2953,14 @@ static struct hvm_function_table __initdata_cf_clobber vmx_function_table = {
     .altp2m_vcpu_emulate_ve = vmx_vcpu_emulate_ve,
     .altp2m_vcpu_emulate_vmfunc = vmx_vcpu_emulate_vmfunc,
 #endif
+
+#ifdef CONFIG_VMTRACE
     .vmtrace_control = vmtrace_control,
     .vmtrace_output_position = vmtrace_output_position,
     .vmtrace_set_option = vmtrace_set_option,
     .vmtrace_get_option = vmtrace_get_option,
     .vmtrace_reset = vmtrace_reset,
+#endif
 
     .get_reg = vmx_get_reg,
     .set_reg = vmx_set_reg,

xen/arch/x86/include/asm/guest-msr.h

@@ -50,6 +50,7 @@ struct vcpu_msrs
         };
     } misc_features_enables;
 
+#ifdef CONFIG_VMTRACE
     /*
      * 0x00000560 ... 57x - MSR_RTIT_*
      *
@@ -81,6 +82,7 @@ struct vcpu_msrs
             };
         };
     } rtit;
+#endif
 
     /*
      * 0x000006e1 - MSR_PKRS - Protection Key Supervisor.

xen/arch/x86/include/asm/hvm/hvm.h

@@ -236,12 +236,14 @@ struct hvm_function_table {
     int (*altp2m_vcpu_emulate_vmfunc)(const struct cpu_user_regs *regs);
 #endif
 
+#ifdef CONFIG_VMTRACE
     /* vmtrace */
     int (*vmtrace_control)(struct vcpu *v, bool enable, bool reset);
     int (*vmtrace_output_position)(struct vcpu *v, uint64_t *pos);
     int (*vmtrace_set_option)(struct vcpu *v, uint64_t key, uint64_t value);
     int (*vmtrace_get_option)(struct vcpu *v, uint64_t key, uint64_t *value);
     int (*vmtrace_reset)(struct vcpu *v);
+#endif
 
     uint64_t (*get_reg)(struct vcpu *v, unsigned int reg);
     void (*set_reg)(struct vcpu *v, unsigned int reg, uint64_t val);
@@ -741,6 +743,7 @@ static inline bool altp2m_vcpu_emulate_ve(struct vcpu *v)
 bool altp2m_vcpu_emulate_ve(struct vcpu *v);
 #endif /* CONFIG_ALTP2M */
 
+#ifdef CONFIG_VMTRACE
 static inline int hvm_vmtrace_control(struct vcpu *v, bool enable, bool reset)
 {
     if ( hvm_funcs.vmtrace_control )
@@ -775,11 +778,20 @@ static inline int hvm_vmtrace_get_option(
 
     return -EOPNOTSUPP;
 }
+#else
+/*
+ * Function declaration(s) here are used without definition(s) to make compiler
+ * happy when VMTRACE=n, compiler DCE will eliminate unused code.
+ */
+int hvm_vmtrace_output_position(struct vcpu *v, uint64_t *pos);
+#endif
 
 static inline int hvm_vmtrace_reset(struct vcpu *v)
 {
+#ifdef CONFIG_VMTRACE
     if ( hvm_funcs.vmtrace_reset )
         return alternative_call(hvm_funcs.vmtrace_reset, v);
+#endif
 
     return -EOPNOTSUPP;
 }
@@ -937,28 +949,6 @@ static inline bool hvm_has_set_descriptor_access_exiting(void)
     return false;
 }
 
-static inline int hvm_vmtrace_control(struct vcpu *v, bool enable, bool reset)
-{
-    return -EOPNOTSUPP;
-}
-
-static inline int hvm_vmtrace_output_position(struct vcpu *v, uint64_t *pos)
-{
-    return -EOPNOTSUPP;
-}
-
-static inline int hvm_vmtrace_set_option(
-    struct vcpu *v, uint64_t key, uint64_t value)
-{
-    return -EOPNOTSUPP;
-}
-
-static inline int hvm_vmtrace_get_option(
-    struct vcpu *v, uint64_t key, uint64_t *value)
-{
-    return -EOPNOTSUPP;
-}
-
 static inline uint64_t hvm_get_reg(struct vcpu *v, unsigned int reg)
 {
     ASSERT_UNREACHABLE();

xen/arch/x86/include/asm/hvm/vmx/vmcs.h

@@ -154,8 +154,10 @@ struct vmx_vcpu {
     /* Do we need to tolerate a spurious EPT_MISCONFIG VM exit? */
     bool                 ept_spurious_misconfig;
 
+#ifdef CONFIG_VMTRACE
     /* Processor Trace configured and enabled for the vcpu. */
     bool                 ipt_active;
+#endif
 
     /* Is the guest in real mode? */
     uint8_t              vmx_realmode;

xen/arch/x86/mm/mem_sharing.c

@@ -1891,7 +1891,9 @@ static int fork(struct domain *cd, struct domain *d)
         domain_pause(d);
         cd->max_pages = d->max_pages;
         *cd->arch.cpu_policy = *d->arch.cpu_policy;
+#ifdef CONFIG_VMTRACE
         cd->vmtrace_size = d->vmtrace_size;
+#endif
         cd->parent = d;
     }
 

xen/arch/x86/vm_event.c

@@ -253,7 +253,9 @@ void vm_event_fill_regs(vm_event_request_t *req)
     req->data.regs.x86.shadow_gs = ctxt.shadow_gs;
     req->data.regs.x86.dr6 = ctxt.dr6;
 
-    if ( hvm_vmtrace_output_position(curr, &req->data.regs.x86.vmtrace_pos) != 1 )
+    if ( IS_ENABLED(CONFIG_VMTRACE) &&
+         hvm_vmtrace_output_position(curr,
+                                     &req->data.regs.x86.vmtrace_pos) != 1 )
         req->data.regs.x86.vmtrace_pos = ~0;
 #endif
 }
@@ -303,12 +305,12 @@ void vm_event_emulate_check(struct vcpu *v, vm_event_response_t *rsp)
 #endif
 }
 
+#ifdef CONFIG_VMTRACE
 void vm_event_reset_vmtrace(struct vcpu *v)
 {
-#ifdef CONFIG_HVM
     hvm_vmtrace_reset(v);
-#endif
 }
+#endif
 
 /*
  * Local variables:

xen/common/domain.c

@@ -135,7 +135,9 @@ struct vcpu *idle_vcpu[NR_CPUS] __read_mostly;
 
 vcpu_info_t dummy_vcpu_info;
 
+#ifdef CONFIG_VMTRACE
 bool __read_mostly vmtrace_available;
+#endif
 
 bool __read_mostly vpmu_is_available;
 
@@ -358,6 +360,7 @@ static void free_vcpu_struct(struct vcpu *v)
 
 static void vmtrace_free_buffer(struct vcpu *v)
 {
+#ifdef CONFIG_VMTRACE
     const struct domain *d = v->domain;
     struct page_info *pg = v->vmtrace.pg;
     unsigned int i;
@@ -372,10 +375,12 @@ static void vmtrace_free_buffer(struct vcpu *v)
         put_page_alloc_ref(&pg[i]);
         put_page_and_type(&pg[i]);
     }
+#endif
 }
 
 static int vmtrace_alloc_buffer(struct vcpu *v)
 {
+#ifdef CONFIG_VMTRACE
     struct domain *d = v->domain;
     struct page_info *pg;
     unsigned int i;
@@ -417,6 +422,9 @@ static int vmtrace_alloc_buffer(struct vcpu *v)
     }
 
     return -ENODATA;
+#else
+    return 0;
+#endif
 }
 
 /*
@@ -884,7 +892,9 @@ struct domain *domain_create(domid_t domid,
         ASSERT(!config->altp2m.nr);
 #endif
 
+#ifdef CONFIG_VMTRACE
         d->vmtrace_size = config->vmtrace_size;
+#endif
     }
 
     /* Sort out our idea of is_control_domain(). */

xen/common/memory.c

@@ -1259,8 +1259,10 @@ static unsigned int resource_max_frames(const struct domain *d,
     case XENMEM_resource_ioreq_server:
         return ioreq_server_max_frames(d);
 
+#ifdef CONFIG_VMTRACE
     case XENMEM_resource_vmtrace_buf:
         return d->vmtrace_size >> PAGE_SHIFT;
+#endif
 
     default:
         return 0;
@@ -1302,6 +1304,7 @@ static int acquire_ioreq_server(struct domain *d,
 #endif
 }
 
+#ifdef CONFIG_VMTRACE
 static int acquire_vmtrace_buf(
     struct domain *d, unsigned int id, unsigned int frame,
     unsigned int nr_frames, xen_pfn_t mfn_list[])
@@ -1324,6 +1327,7 @@ static int acquire_vmtrace_buf(
 
     return nr_frames;
 }
+#endif
 
 /*
  * Returns -errno on error, or positive in the range [1, nr_frames] on
@@ -1342,8 +1346,10 @@ static int _acquire_resource(
     case XENMEM_resource_ioreq_server:
         return acquire_ioreq_server(d, id, frame, nr_frames, mfn_list);
 
+#ifdef CONFIG_VMTRACE
     case XENMEM_resource_vmtrace_buf:
         return acquire_vmtrace_buf(d, id, frame, nr_frames, mfn_list);
+#endif
 
     default:
         ASSERT_UNREACHABLE();

xen/common/vm_event.c

@@ -441,7 +441,8 @@ static int vm_event_resume(struct domain *d, struct vm_event_domain *ved)
             if ( rsp.flags & VM_EVENT_FLAG_GET_NEXT_INTERRUPT )
                 vm_event_monitor_next_interrupt(v);
 
-            if ( rsp.flags & VM_EVENT_FLAG_RESET_VMTRACE )
+            if ( IS_ENABLED(CONFIG_VMTRACE) &&
+                 (rsp.flags & VM_EVENT_FLAG_RESET_VMTRACE) )
                 vm_event_reset_vmtrace(v);
 
             if ( rsp.flags & VM_EVENT_FLAG_VCPU_PAUSED )

xen/include/xen/domain.h

@@ -183,7 +183,11 @@ void vnuma_destroy(struct vnuma_info *vnuma);
 static inline void vnuma_destroy(struct vnuma_info *vnuma) { ASSERT(!vnuma); }
 #endif
 
+#ifdef CONFIG_VMTRACE
 extern bool vmtrace_available;
+#else
+#define vmtrace_available false
+#endif
 
 extern bool vpmu_is_available;
 

xen/include/xen/sched.h

@@ -300,9 +300,11 @@ struct vcpu
     /* vPCI per-vCPU area, used to store data for long running operations. */
     struct vpci_vcpu vpci;
 
+#ifdef CONFIG_VMTRACE
     struct {
         struct page_info *pg; /* One contiguous allocation of d->vmtrace_size */
     } vmtrace;
+#endif
 
     struct arch_vcpu arch;
 
@@ -626,7 +628,9 @@ struct domain
     unsigned int nr_altp2m;    /* Number of altp2m tables. */
 #endif
 
+#ifdef CONFIG_VMTRACE
     unsigned int vmtrace_size; /* Buffer size in bytes, or 0 to disable. */
+#endif
 
 #ifdef CONFIG_ARGO
     /* Argo interdomain communication support */