Re: [Xen-devel] [PATCH v3 2/3] x86/VPMU: Disable VPMU when NMI watchdog is on

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/01/15 17:15, Boris Ostrovsky wrote:
> NMI watchdog sets APIC_LVTPC register to generate an NMI when PMU counter
> overflow occurs. This may be overwritten by VPMU code later, effectively
> turning off the watchdog.
>
> We should disable VPMU when NMI watchdog is running.
>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

> ---
>  docs/misc/xen-command-line.markdown |  2 ++
>  xen/arch/x86/hvm/vpmu.c             | 13 +++++++++++++
>  2 files changed, 15 insertions(+)
>
> diff --git a/docs/misc/xen-command-line.markdown 
> b/docs/misc/xen-command-line.markdown
> index 2274e74..bc316be 100644
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -1346,6 +1346,8 @@ wrong behaviour (see handle\_pmc\_quirk()).
>  If 'vpmu=bts' is specified the virtualisation of the Branch Trace Store (BTS)
>  feature is switched on on Intel processors supporting this feature.
>  
> +Note that if **watchdog** option is also specified vpmu will be turned off.
> +
>  *Warning:*
>  As the BTS virtualisation is not 100% safe and because of the nehalem quirk
>  don't use the vpmu flag on production systems with Intel cpus!
> diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c
> index 63b2158..b2e8e65 100644
> --- a/xen/arch/x86/hvm/vpmu.c
> +++ b/xen/arch/x86/hvm/vpmu.c
> @@ -24,6 +24,7 @@
>  #include <asm/regs.h>
>  #include <asm/types.h>
>  #include <asm/msr.h>
> +#include <asm/nmi.h>
>  #include <asm/hvm/support.h>
>  #include <asm/hvm/vmx/vmx.h>
>  #include <asm/hvm/vmx/vmcs.h>
> @@ -288,3 +289,15 @@ void vpmu_dump(struct vcpu *v)
>          vpmu->arch_vpmu_ops->arch_vpmu_dump(v);
>  }
>  
> +static int __init vpmu_init(void)
> +{
> +    /* NMI watchdog uses LVTPC and HW counter */
> +    if ( opt_watchdog && opt_vpmu_enabled )
> +    {
> +        printk(XENLOG_WARNING "NMI watchdog is enabled. Turning VPMU 
> off.\n");
> +        opt_vpmu_enabled = 0;
> +    }
> +
> +    return 0;
> +}
> +__initcall(vpmu_init);


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