Re: [PATCH v3 3/3] xen: Expose the PMU to the guests

[Nick Rosbrook <rosbrookn@xxxxxxxxx>]

On Fri, Oct 08, 2021 at 10:19:33AM +0200, Michal Orzel wrote:
> Add parameter vpmu to xl domain configuration syntax
> to enable the access to PMU registers by disabling
> the PMU traps(currently only for ARM).
> 
> The current status is that the PMU registers are not
> virtualized and the physical registers are directly
> accessible when this parameter is enabled. There is no
> interrupt support and Xen will not save/restore the
> register values on context switches.
> 
> Please note that this feature is experimental.
> 
> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
> Signed-off-by: Julien Grall <julien@xxxxxxx>
> ---
> Changes since v2:
> -remove redundant check from x86 code
> -do not define bit position and mask separately
> Changes since v1:
> -modify vpmu parameter to be common rather than arch specific
> ---
>  docs/man/xl.cfg.5.pod.in             | 17 +++++++++++++++++
>  tools/golang/xenlight/helpers.gen.go |  6 ++++++
>  tools/golang/xenlight/types.gen.go   |  1 +
>  tools/include/libxl.h                |  6 ++++++
>  tools/libs/light/libxl_create.c      |  4 ++++
>  tools/libs/light/libxl_types.idl     |  2 ++
>  tools/ocaml/libs/xc/xenctrl.ml       |  1 +
>  tools/ocaml/libs/xc/xenctrl.mli      |  1 +
>  tools/xl/xl_parse.c                  |  2 ++
>  xen/arch/arm/domain.c                | 10 ++++++++--
>  xen/arch/arm/setup.c                 |  1 +
>  xen/common/domain.c                  |  9 ++++++++-
>  xen/include/asm-arm/domain.h         |  1 +
>  xen/include/public/domctl.h          |  4 +++-
>  14 files changed, 61 insertions(+), 4 deletions(-)
> 
> diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
> index 4b1e3028d2..55c4881205 100644
> --- a/docs/man/xl.cfg.5.pod.in
> +++ b/docs/man/xl.cfg.5.pod.in
> @@ -690,6 +690,23 @@ default.
>  B<NOTE>: Acceptable values are platform specific.  For Intel Processor
>  Trace, this value must be a power of 2 between 4k and 16M.
>  
> +=item B<vpmu=BOOLEAN>
> +
> +Currently ARM only.
> +
> +Specifies whether to enable the access to PMU registers by disabling
> +the PMU traps.
> +
> +The PMU registers are not virtualized and the physical registers are directly
> +accessible when this parameter is enabled. There is no interrupt support and
> +Xen will not save/restore the register values on context switches.
> +
> +vPMU, by design and purpose, exposes system level performance
> +information to the guest. Only to be used by sufficiently privileged
> +domains. This feature is currently in experimental state.
> +
> +If this option is not specified then it will default to B<false>.
> +
>  =back
>  
>  =head2 Devices
> diff --git a/tools/golang/xenlight/helpers.gen.go 
> b/tools/golang/xenlight/helpers.gen.go
> index c8669837d8..2449580bad 100644
> --- a/tools/golang/xenlight/helpers.gen.go
> +++ b/tools/golang/xenlight/helpers.gen.go
> @@ -1119,6 +1119,9 @@ return fmt.Errorf("converting field ArchX86.MsrRelaxed: 
> %v", err)
>  }
>  x.Altp2M = Altp2MMode(xc.altp2m)
>  x.VmtraceBufKb = int(xc.vmtrace_buf_kb)
> +if err := x.Vpmu.fromC(&xc.vpmu);err != nil {
> +return fmt.Errorf("converting field Vpmu: %v", err)
> +}
>  
>   return nil}
>  
> @@ -1600,6 +1603,9 @@ return fmt.Errorf("converting field ArchX86.MsrRelaxed: 
> %v", err)
>  }
>  xc.altp2m = C.libxl_altp2m_mode(x.Altp2M)
>  xc.vmtrace_buf_kb = C.int(x.VmtraceBufKb)
> +if err := x.Vpmu.toC(&xc.vpmu); err != nil {
> +return fmt.Errorf("converting field Vpmu: %v", err)
> +}
>  
>   return nil
>   }
> diff --git a/tools/golang/xenlight/types.gen.go 
> b/tools/golang/xenlight/types.gen.go
> index 45f2cba3d2..b2e8bd1a85 100644
> --- a/tools/golang/xenlight/types.gen.go
> +++ b/tools/golang/xenlight/types.gen.go
> @@ -521,6 +521,7 @@ MsrRelaxed Defbool
>  }
>  Altp2M Altp2MMode
>  VmtraceBufKb int
> +Vpmu Defbool
>  }
>  
>  type DomainBuildInfoTypeUnion interface {

For the golang re-gen,

Acked-by: Nick Rosbrook <rosbrookn@xxxxxxxxxxxx>

Thanks,
NR