[Xen-devel] [PATCH v13 for-xen-4.5 19/21] x86/VPMU: Add privileged PMU mode

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Add support for privileged PMU mode (XENPMU_MODE_ALL) which allows privileged
domain (dom0) profile both itself (and the hypervisor) and the guests. While
this mode is on profiling in guests is disabled.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Reviewed-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/vpmu.c  | 30 ++++++++++++++++++++++--------
 xen/arch/x86/traps.c     | 12 ++++++++++++
 xen/include/public/pmu.h |  3 +++
 3 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c
index 74c5faa..f75a54a 100644
--- a/xen/arch/x86/hvm/vpmu.c
+++ b/xen/arch/x86/hvm/vpmu.c
@@ -99,7 +99,9 @@ int vpmu_do_msr(unsigned int msr, uint64_t *msr_content,
     struct arch_vpmu_ops *ops;
     int ret = 0;
 
-    if ( !(vpmu_mode & (XENPMU_MODE_SELF | XENPMU_MODE_HV)) )
+    if ( (vpmu_mode == XENPMU_MODE_OFF) ||
+         ((vpmu_mode & XENPMU_MODE_ALL) &&
+          !is_hardware_domain(current->domain)) )
         return 0;
 
     curr = current;
@@ -144,8 +146,12 @@ int vpmu_do_interrupt(struct cpu_user_regs *regs)
     struct vcpu *sampled = current, *sampling;
     struct vpmu_struct *vpmu;
 
-    /* dom0 will handle interrupt for special domains (e.g. idle domain) */
-    if ( sampled->domain->domain_id >= DOMID_FIRST_RESERVED )
+    /*
+     * dom0 will handle interrupt for special domains (e.g. idle domain) or,
+     * in XENPMU_MODE_ALL, for everyone.
+     */
+    if ( (vpmu_mode & XENPMU_MODE_ALL) ||
+         (sampled->domain->domain_id >= DOMID_FIRST_RESERVED) )
     {
         sampling = choose_hwdom_vcpu();
         if ( !sampling )
@@ -155,12 +161,12 @@ int vpmu_do_interrupt(struct cpu_user_regs *regs)
         sampling = sampled;
 
     vpmu = vcpu_vpmu(sampling);
-    if ( !is_hvm_vcpu(sampling) )
+    if ( !is_hvm_vcpu(sampling) || (vpmu_mode & XENPMU_MODE_ALL) )
     {
         /* PV(H) guest */
         const struct cpu_user_regs *cur_regs;
         uint64_t *flags = &vpmu->xenpmu_data->pmu.pmu_flags;
-        uint32_t domid = DOMID_SELF;
+        uint32_t domid;
 
         if ( !vpmu->xenpmu_data )
             return 0;
@@ -169,6 +175,7 @@ int vpmu_do_interrupt(struct cpu_user_regs *regs)
             return 1;
 
         if ( is_pvh_vcpu(sampling) &&
+             !(vpmu_mode & XENPMU_MODE_ALL) &&
              !vpmu->arch_vpmu_ops->do_interrupt(regs) )
             return 0;
 
@@ -177,6 +184,11 @@ int vpmu_do_interrupt(struct cpu_user_regs *regs)
         vpmu->arch_vpmu_ops->arch_vpmu_save(sampling);
         vpmu_reset(vpmu, VPMU_CONTEXT_SAVE | VPMU_CONTEXT_LOADED);
 
+        if ( sampled == sampling )
+            domid = DOMID_SELF;
+        else
+            domid = sampled->domain->domain_id;
+
         /* Store appropriate registers in xenpmu_data */
         /* FIXME: 32-bit PVH should go here as well */
         if ( is_pv_32bit_vcpu(sampling) )
@@ -618,11 +630,13 @@ long do_xenpmu_op(int op, 
XEN_GUEST_HANDLE_PARAM(xen_pmu_params_t) arg)
         if ( copy_from_guest(&pmu_params, arg, 1) )
             return -EFAULT;
 
-        if ( pmu_params.val & ~(XENPMU_MODE_SELF | XENPMU_MODE_HV) )
+        if ( pmu_params.val & ~(XENPMU_MODE_SELF | XENPMU_MODE_HV |
+                                XENPMU_MODE_ALL) )
             return -EINVAL;
 
         /* 32-bit dom0 can only sample itself */
-        if ( is_pv_32bit_vcpu(current) && (pmu_params.val & XENPMU_MODE_HV) )
+        if ( is_pv_32bit_vcpu(current) &&
+             (pmu_params.val & (XENPMU_MODE_HV | XENPMU_MODE_ALL)) )
             return -EINVAL;
 
         /*
@@ -636,7 +650,7 @@ long do_xenpmu_op(int op, 
XEN_GUEST_HANDLE_PARAM(xen_pmu_params_t) arg)
         current_mode = vpmu_mode;
         vpmu_mode = pmu_params.val;
 
-        if ( vpmu_mode == XENPMU_MODE_OFF )
+        if ( (vpmu_mode == XENPMU_MODE_OFF) || (vpmu_mode == XENPMU_MODE_ALL) )
         {
             /*
              * Make sure all (non-dom0) VCPUs have unloaded their VPMUs. This
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 70477b2..663b44f 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2579,6 +2579,10 @@ static int emulate_privileged_op(struct cpu_user_regs 
*regs)
         case MSR_AMD_FAM15H_EVNTSEL0...MSR_AMD_FAM15H_PERFCTR5:
                 if ( vpmu_msr || (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) )
                 {
+                    if ( (vpmu_mode & XENPMU_MODE_ALL) &&
+                         !is_hardware_domain(v->domain) )
+                        break;
+
                     if ( vpmu_do_wrmsr(regs->ecx, msr_content, 0) )
                         goto fail;
                 }
@@ -2702,6 +2706,14 @@ static int emulate_privileged_op(struct cpu_user_regs 
*regs)
         case MSR_AMD_FAM15H_EVNTSEL0...MSR_AMD_FAM15H_PERFCTR5:
                 if ( vpmu_msr || (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) )
                 {
+                    if ( (vpmu_mode & XENPMU_MODE_ALL) &&
+                         !is_hardware_domain(v->domain) )
+                    {
+                        /* Don't leak PMU MSRs to unprivileged domains */
+                        regs->eax = regs->edx = 0;
+                        break;
+                    }
+
                     if ( vpmu_do_rdmsr(regs->ecx, &msr_content) )
                         goto fail;
 
diff --git a/xen/include/public/pmu.h b/xen/include/public/pmu.h
index b4bf7ff..25b089d 100644
--- a/xen/include/public/pmu.h
+++ b/xen/include/public/pmu.h
@@ -51,10 +51,13 @@ DEFINE_XEN_GUEST_HANDLE(xen_pmu_params_t);
  * - XENPMU_MODE_SELF:  Guests can profile themselves
  * - XENPMU_MODE_HV:    Guests can profile themselves, dom0 profiles
  *                      itself and Xen
+ * - XENPMU_MODE_ALL:   Only dom0 has access to VPMU and it profiles
+ *                      everyone: itself, the hypervisor and the guests.
  */
 #define XENPMU_MODE_OFF           0
 #define XENPMU_MODE_SELF          (1<<0)
 #define XENPMU_MODE_HV            (1<<1)
+#define XENPMU_MODE_ALL           (1<<2)
 
 /*
  * PMU features:
-- 
1.8.1.4


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