Re: [PATCH v19 13/14] x86/VPMU: Add privileged PMU mode

[Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>]

Am Dienstag 17 März 2015, 10:54:10 schrieb Boris Ostrovsky:
> 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@oracle.com>

Reviewed-by: Dietmar Hahn <dietmar.hahn@ts.fujitsu.com>

Dietmar.

> ---
> Changes in v19:
> * Slightly different mode changing logic in xenpmu_op() since we no longer
>   allow mode changes while VPMUs are active
> 
>  xen/arch/x86/hvm/vpmu.c  | 34 +++++++++++++++++++++++++---------
>  xen/arch/x86/traps.c     | 13 +++++++++++++
>  xen/include/public/pmu.h |  3 +++
>  3 files changed, 41 insertions(+), 9 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c
> index beed956..71c5063 100644
> --- a/xen/arch/x86/hvm/vpmu.c
> +++ b/xen/arch/x86/hvm/vpmu.c
> @@ -111,7 +111,9 @@ int vpmu_do_msr(unsigned int msr, uint64_t *msr_content,
>      const struct arch_vpmu_ops *ops;
>      int ret = 0;
>  
> -    if ( vpmu_mode == XENPMU_MODE_OFF )
> +    if ( (vpmu_mode == XENPMU_MODE_OFF) ||
> +         ((vpmu_mode & XENPMU_MODE_ALL) &&
> +          !is_hardware_domain(current->domain)) )
>          goto nop;
>  
>      curr = current;
> @@ -166,8 +168,12 @@ void 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 )
> @@ -177,17 +183,18 @@ void 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;
>  
>          if ( is_pvh_vcpu(sampling) &&
> +             !(vpmu_mode & XENPMU_MODE_ALL) &&
>               !vpmu->arch_vpmu_ops->do_interrupt(regs) )
>              return;
>  
> @@ -204,6 +211,11 @@ void vpmu_do_interrupt(struct cpu_user_regs *regs)
>          else
>              *flags = PMU_SAMPLE_PV;
>  
> +        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) )
> @@ -232,7 +244,8 @@ void vpmu_do_interrupt(struct cpu_user_regs *regs)
>  
>              if ( (vpmu_mode & XENPMU_MODE_SELF) )
>                  cur_regs = guest_cpu_user_regs();
> -            else if ( !guest_mode(regs) && is_hardware_domain(sampling->domain) )
> +            else if ( !guest_mode(regs) &&
> +                      is_hardware_domain(sampling->domain) )
>              {
>                  cur_regs = regs;
>                  domid = DOMID_XEN;
> @@ -508,7 +521,8 @@ static int pvpmu_init(struct domain *d, xen_pmu_params_t *params)
>      struct page_info *page;
>      uint64_t gfn = params->val;
>  
> -    if ( vpmu_mode == XENPMU_MODE_OFF )
> +    if ( (vpmu_mode == XENPMU_MODE_OFF) ||
> +         ((vpmu_mode & XENPMU_MODE_ALL) && !is_hardware_domain(d)) )
>          return -EINVAL;
>  
>      if ( (params->vcpu >= d->max_vcpus) || (d->vcpu == NULL) ||
> @@ -627,12 +641,14 @@ long do_xenpmu_op(unsigned int op, XEN_GUEST_HANDLE_PARAM(xen_pmu_params_t) arg)
>      {
>      case XENPMU_mode_set:
>      {
> -        if ( (pmu_params.val & ~(XENPMU_MODE_SELF | XENPMU_MODE_HV)) ||
> +        if ( (pmu_params.val &
> +              ~(XENPMU_MODE_SELF | XENPMU_MODE_HV | XENPMU_MODE_ALL)) ||
>               (hweight64(pmu_params.val) > 1) )
>              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;
>  
>          spin_lock(&vpmu_lock);
> diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
> index 1eb7bb4..8a40deb 100644
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -2653,6 +2653,10 @@ 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;
>                  }
> @@ -2776,6 +2780,15 @@ 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, &val) )
>                          goto fail;
>  
> diff --git a/xen/include/public/pmu.h b/xen/include/public/pmu.h
> index db5321a..a83ae71 100644
> --- a/xen/include/public/pmu.h
> +++ b/xen/include/public/pmu.h
> @@ -52,10 +52,13 @@ 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:
> 

-- 
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