RE: [PATCH] hv: vmbus_drv: detect hyperv through x86_hyper

[KY Srinivasan <kys@microsoft.com>]

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Friday, August 31, 2012 1:33 AM
> To: devel@linuxdriverproject.org; linux-kernel@vger.kernel.org
> Cc: Jason Wang; KY Srinivasan; Haiyang Zhang
> Subject: [PATCH] hv: vmbus_drv: detect hyperv through x86_hyper
> 
> There are two reasons we need to use x86_hyper instead of
> query_hypervisor_presence():
> 
> - Not only hyperv but also other hypervisors such as kvm would set
>   X86_FEATURE_HYTPERVISOR, so query_hypervisor_presence() will return true
> even
>   in kvm. This may cause extra delay of 5 seconds before failing the probing in
>   kvm guest.
> - The hypervisor has been detected in init_hypervisor(), so no need to do the
>   work again.
> 
> Cc: "K. Y. Srinivasan" <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Thanks Jason.

Acked-by: K. Y. Srinivasan <kys@microsoft.com>

> ---
>  drivers/hv/vmbus_drv.c |   25 ++-----------------------
>  1 files changed, 2 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index f40dd57..8e1a9ec 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -34,6 +34,7 @@
>  #include <linux/completion.h>
>  #include <linux/hyperv.h>
>  #include <asm/hyperv.h>
> +#include <asm/hypervisor.h>
>  #include "hyperv_vmbus.h"
> 
> 
> @@ -719,33 +720,11 @@ static struct acpi_driver vmbus_acpi_driver = {
>  	},
>  };
> 
> -/*
> - * query_hypervisor_presence
> - * - Query the cpuid for presence of windows hypervisor
> - */
> -static int query_hypervisor_presence(void)
> -{
> -	unsigned int eax;
> -	unsigned int ebx;
> -	unsigned int ecx;
> -	unsigned int edx;
> -	unsigned int op;
> -
> -	eax = 0;
> -	ebx = 0;
> -	ecx = 0;
> -	edx = 0;
> -	op = HVCPUID_VERSION_FEATURES;
> -	cpuid(op, &eax, &ebx, &ecx, &edx);
> -
> -	return ecx & HV_PRESENT_BIT;
> -}
> -
>  static int __init hv_acpi_init(void)
>  {
>  	int ret, t;
> 
> -	if (!query_hypervisor_presence())
> +	if (x86_hyper != &x86_hyper_ms_hyperv)
>  		return -ENODEV;
> 
>  	init_completion(&probe_event);
> --
> 1.7.1
> 
> 
>