linux-kernel - Re: [PATCH 1/3] xen: off by one error in xen/setup.c

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Date:	Tue, 9 Aug 2011 12:55:12 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Igor Mammedov <imammedo@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] xen: off by one error in xen/setup.c

On Tue, Aug 02, 2011 at 11:45:23AM +0200, Igor Mammedov wrote:
> Do not try to initialize pfn beyond of available address space.

Actually, thinking about this I don't think this is right.

We want to initialize the P2M space _at_ the xen_max_p2m_pfn. With
your patch we would only initialize it up to xen_max_p2m_pfn-1 - so
the last PFN would not be set to INVALID_P2M_ENTRY.

> 
> Signed-off-by: Igor Mammedov <imammedo@...hat.com>
> ---
>  arch/x86/xen/setup.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index 60aeeb5..2221b05 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -69,7 +69,7 @@ static void __init xen_add_extra_mem(unsigned long pages)
>  
>  	xen_max_p2m_pfn = PFN_DOWN(extra_start + size);
>  
> -	for (pfn = PFN_DOWN(extra_start); pfn <= xen_max_p2m_pfn; pfn++)
> +	for (pfn = PFN_DOWN(extra_start); pfn < xen_max_p2m_pfn; ++pfn)
>  		__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
>  }
>  
> -- 
> 1.7.5
> 
> --
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