Re: [PATCH 3/6] x86: Add nopv parameter to disable PV extensions

[Juergen Gross]

On 23.06.19 15:01, Zhenzhong Duan wrote:
> In virtualization environment, PV extensions (drivers, interrupts,
> timers, etc) are enabled in the majority of use cases which is the
> best option.
>
> However, in some cases (kexec not fully working, benchmarking)
> we want to disable PV extensions. As such introduce the
> 'nopv' parameter that will do it.
>
> There is already 'xen_nopv' parameter for XEN platform but not for
> others. 'xen_nopv' can then be removed with this change.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> ---
>   Documentation/admin-guide/kernel-parameters.txt |  4 ++++
>   arch/x86/kernel/cpu/hypervisor.c                | 11 +++++++++++
>   2 files changed, 15 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 138f666..b352f36 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -5268,6 +5268,10 @@
>   			improve timer resolution at the expense of processing
>   			more timer interrupts.
>   
> +	nopv=		[X86]
> +			Disables the PV optimizations forcing the guest to run
> +			as generic guest with no PV drivers.
> +
>   	xirc2ps_cs=	[NET,PCMCIA]
>   			Format:
>   			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
> diff --git a/arch/x86/kernel/cpu/hypervisor.c b/arch/x86/kernel/cpu/hypervisor.c
> index 479ca47..4f2c875 100644
> --- a/arch/x86/kernel/cpu/hypervisor.c
> +++ b/arch/x86/kernel/cpu/hypervisor.c
> @@ -85,10 +85,21 @@ static void __init copy_array(const void *src, void *target, unsigned int size)
>   			to[i] = from[i];
>   }
>   
> +static bool nopv;
> +static __init int xen_parse_nopv(char *arg)

You really don't want to use the "xen_" prefix here.


Juergen