linux-kernel - Re: [PATCH] perf/x86: Disable uncore on virtualized CPU.

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Message-ID: <20120905063524.GA20710@gmail.com>
Date:	Wed, 5 Sep 2012 08:35:24 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	a.p.zijlstra@...llo.nl, eranian@...gle.com, mingo@...e.hu,
	andi@...stfloor.org, avi@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf/x86: Disable uncore on virtualized CPU.


* Yan, Zheng <zheng.z.yan@...el.com> wrote:

> From: "Yan, Zheng" <zheng.z.yan@...el.com>
> 
> Initializing uncore PMU on virtualized CPU may hang the kernel.
> This is because kvm does not emulate the entire hardware. Thers
> are lots of uncore related MSRs, making kvm enumerate them all
> is a non-trival task. So just disable uncore on virtualized CPU.
> 
> Signed-off-by: Yan, Zheng <zheng.z.yan@...el.com>
> ---
>  arch/x86/kernel/cpu/perf_event_intel_uncore.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> index 0a55710..2f005ba 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
> @@ -2898,6 +2898,9 @@ static int __init intel_uncore_init(void)
>  	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
>  		return -ENODEV;
>  
> +	if (cpu_has_hypervisor)
> +		return -ENODEV;
> +
>  	ret = uncore_pci_init();
>  	if (ret)
>  		goto fail;

Cannot the presence of the uncore hardware be detected in a 
cleaner fashion, via the PCI config space and such?

Thanks,

	Ingo
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