Re: [Xen-devel] [PATCH for-next RFC 7/8] x86: introduce CONFIG_HYPERV and hyperv directory

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Sep 23, 2019 at 11:09:30AM +0100, Wei Liu wrote:
> We use the same code structure as we did for Xen code.
> 
> As starters, detect Hyper-V in probe_hyperv. More complex
> functionality will be added later.
> 
> Signed-off-by: Wei Liu <liuwe@xxxxxxxxxxxxx>
> ---
>  xen/arch/x86/Kconfig               |  9 +++++
>  xen/arch/x86/guest/Makefile        |  1 +
>  xen/arch/x86/guest/hyperv/Makefile |  1 +
>  xen/arch/x86/guest/hyperv/hyperv.c | 63 ++++++++++++++++++++++++++++++
>  xen/arch/x86/guest/hypervisor.c    |  3 +-
>  xen/include/asm-x86/guest.h        |  1 +
>  xen/include/asm-x86/guest/hyperv.h | 48 +++++++++++++++++++++++
>  7 files changed, 125 insertions(+), 1 deletion(-)
>  create mode 100644 xen/arch/x86/guest/hyperv/Makefile
>  create mode 100644 xen/arch/x86/guest/hyperv/hyperv.c
>  create mode 100644 xen/include/asm-x86/guest/hyperv.h
> 
> diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
> index 584bdc1bb8..c5a93babfe 100644
> --- a/xen/arch/x86/Kconfig
> +++ b/xen/arch/x86/Kconfig
> @@ -163,6 +163,15 @@ endchoice
>  config GUEST
>       bool
>  
> +config HYPERV_GUEST
> +     def_bool n
> +     select GUEST
> +     prompt "Hyper-V Guest"
> +     ---help---
> +       Support for Xen detecting when it is running under Hyper-V.
> +
> +       If unsure, say N.
> +
>  config XEN_GUEST
>       def_bool n
>       select GUEST
> diff --git a/xen/arch/x86/guest/Makefile b/xen/arch/x86/guest/Makefile
> index f63d64bbee..f164196772 100644
> --- a/xen/arch/x86/guest/Makefile
> +++ b/xen/arch/x86/guest/Makefile
> @@ -1,3 +1,4 @@
>  obj-y += hypervisor.o
>  
> +subdir-$(CONFIG_HYPERV_GUEST) += hyperv
>  subdir-$(CONFIG_XEN_GUEST) += xen
> diff --git a/xen/arch/x86/guest/hyperv/Makefile 
> b/xen/arch/x86/guest/hyperv/Makefile
> new file mode 100644
> index 0000000000..68170109a9
> --- /dev/null
> +++ b/xen/arch/x86/guest/hyperv/Makefile
> @@ -0,0 +1 @@
> +obj-y += hyperv.o
> diff --git a/xen/arch/x86/guest/hyperv/hyperv.c 
> b/xen/arch/x86/guest/hyperv/hyperv.c
> new file mode 100644
> index 0000000000..488e9c14a3
> --- /dev/null
> +++ b/xen/arch/x86/guest/hyperv/hyperv.c
> @@ -0,0 +1,63 @@
> +/******************************************************************************
> + * arch/x86/guest/hyperv/hyperv.c
> + *
> + * Support for detecting and running under Hyper-V.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * 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 General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; If not, see <http://www.gnu.org/licenses/>.
> + *
> + * Copyright (c) 2019 Microsoft.
> + */
> +#include <xen/init.h>
> +
> +#include <asm/guest.h>
> +
> +bool __read_mostly hyperv_guest;

static?

> +
> +bool __init probe_hyperv(void)
> +{
> +    uint32_t eax, ebx, ecx, edx;
> +
> +    if ( hyperv_guest )
> +        return true;
> +
> +    cpuid(0x40000000, &eax, &ebx, &ecx, &edx);
> +    if ( (ebx == 0x7263694d) && /* "Micr" */
> +         (ecx == 0x666f736f) && /* "osof" */
> +         (edx == 0x76482074) )  /* "t Hv" */
> +        hyperv_guest = true;
> +
> +    return hyperv_guest;
> +}
> +
> +void __init hyperv_setup(void)
> +{
> +}
> +
> +void hyperv_ap_setup(void)
> +{
> +}
> +
> +void hyperv_resume(void)
> +{
> +}

Seems kind of pointless to add those dummy hyperv_ functions, AFAICT
they don't have any callers yet?

I would prefer that you introduce such dummy callers when they are
used.

Thanks, Roger.

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