linux-kernel - Re: [PATCH 3/4] xen/smp/pvhvm: Don't point per_cpu(xen_vpcu, 33 and larger) to shared

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Date:	Mon, 6 May 2013 16:00:22 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Subject: Re: [PATCH 3/4] xen/smp/pvhvm: Don't point per_cpu(xen_vpcu, 33 and
 larger) to shared_info

On Mon, 6 May 2013, Konrad Rzeszutek Wilk wrote:
> As it will point to some data, but not event channel data (the
> shared_info has an array limited to 32).
> 
> This means that for PVHVM guests with more than 32 VCPUs without
> the usage of VCPUOP_register_info any interrupts to VCPUs
> larger than 32 would have gone unnoticed during early bootup.
> 
> That is OK, as during early bootup, in smp_init we end up calling
> the hotplug mechanism (xen_hvm_cpu_notify) which makes the
> VCPUOP_register_vcpu_info call for all VCPUs and we can receive
> interrupts on VCPUs 33 and further.
> 
> This is just a cleanup.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Acked-by: Stefano Stabellini <stefano.stabellini@...citrix.com>


>  arch/x86/xen/enlighten.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 9b34475..18a4009 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1638,6 +1638,9 @@ void __ref xen_hvm_init_shared_info(void)
>  	 * online but xen_hvm_init_shared_info is run at resume time too and
>  	 * in that case multiple vcpus might be online. */
>  	for_each_online_cpu(cpu) {
> +		/* Leave it to be NULL. */
> +		if (cpu >= MAX_VIRT_CPUS)
> +			continue;
>  		per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
>  	}
>  }
> -- 
> 1.8.1.4
> 
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