Re: [Xen-devel] [PATCH v11 3/9] tools: provide interface for generic MSR access

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Jun 20, 2014 at 10:31:44PM +0800, Dongxiao Xu wrote:
> Xen added a new sysctl hypercall for generic MSR access, and this is the
> tool side change to wrapper the hypercall into xc APIs.
> 

I really like the idea that Jan surfaced. That is use an
cpu bitmap for the operation (see xc_tbuf.c as an example)
and my recent postings http://osdir.com/ml/general/2014-06/msg24386.html.

That way you can define exactly which CPUs you want to do it
at and you can do one nice hypercall that will do it all at
once for you.

> Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> ---
>  tools/libxc/Makefile     |  1 +
>  tools/libxc/xc_msr_x86.c | 53 
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  tools/libxc/xenctrl.h    |  6 ++++++
>  3 files changed, 60 insertions(+)
>  create mode 100644 tools/libxc/xc_msr_x86.c
> 
> diff --git a/tools/libxc/Makefile b/tools/libxc/Makefile
> index a74b19e..fec4aca 100644
> --- a/tools/libxc/Makefile
> +++ b/tools/libxc/Makefile
> @@ -35,6 +35,7 @@ CTRL_SRCS-y       += xc_kexec.c
>  CTRL_SRCS-y       += xtl_core.c
>  CTRL_SRCS-y       += xtl_logger_stdio.c
>  CTRL_SRCS-$(CONFIG_X86) += xc_pagetab.c
> +CTRL_SRCS-$(CONFIG_X86) += xc_msr_x86.c
>  CTRL_SRCS-$(CONFIG_Linux) += xc_linux.c xc_linux_osdep.c
>  CTRL_SRCS-$(CONFIG_SunOS) += xc_solaris.c
>  CTRL_SRCS-$(CONFIG_NetBSD) += xc_netbsd.c
> diff --git a/tools/libxc/xc_msr_x86.c b/tools/libxc/xc_msr_x86.c
> new file mode 100644
> index 0000000..46e77dd
> --- /dev/null
> +++ b/tools/libxc/xc_msr_x86.c
> @@ -0,0 +1,53 @@
> +/*
> + * xc_msr_x86.c
> + *
> + * Generic MSR access API
> + *
> + * Copyright (C) 2014      Intel Corporation
> + * Author Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published
> + * by the Free Software Foundation; version 2.1 only. with the special
> + * exception on linking described in file LICENSE.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + */
> +
> +#include "xc_private.h"
> +
> +int xc_msr_op(xc_interface *xch, uint32_t cpu,
> +              uint32_t nr_ops, xc_msr_data_t *msr_data)
> +{
> +    int rc;
> +    DECLARE_SYSCTL;
> +    DECLARE_HYPERCALL_BOUNCE(msr_data, nr_ops * sizeof(*msr_data),
> +                             XC_HYPERCALL_BUFFER_BOUNCE_BOTH);
> +
> +    if ( xc_hypercall_bounce_pre(xch, msr_data) )
> +        return -1;
> +
> +    sysctl.cmd = XEN_SYSCTL_msr_op;
> +    sysctl.u.msr_op.nr_ops = nr_ops;
> +    sysctl.u.msr_op.cpu = cpu;
> +    set_xen_guest_handle(sysctl.u.msr_op.msr_data, msr_data);
> +
> +    rc = do_sysctl(xch, &sysctl);
> +
> +    xc_hypercall_bounce_post(xch, msr_data);
> +
> +    return rc;
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * tab-width: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
> index 02129f7..50625ca 100644
> --- a/tools/libxc/xenctrl.h
> +++ b/tools/libxc/xenctrl.h
> @@ -2424,4 +2424,10 @@ int xc_kexec_load(xc_interface *xch, uint8_t type, 
> uint16_t arch,
>   */
>  int xc_kexec_unload(xc_interface *xch, int type);
>  
> +#if defined(__i386__) || defined(__x86_64__)
> +typedef xen_sysctl_msr_data_t xc_msr_data_t;
> +int xc_msr_op(xc_interface *xch, uint32_t cpu,
> +    uint32_t nr_ops, xc_msr_data_t *msr_data);
> +#endif
> +
>  #endif /* XENCTRL_H */
> -- 
> 1.8.1.5
> 

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