linux-kernel - Re: [Xen-devel] [PATCH V2 2/3] xen: eliminate scalability issues from initrd handling

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Message-ID: <54199065.1020200@citrix.com>
Date:	Wed, 17 Sep 2014 14:45:09 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>, <konrad.wilk@...cle.com>,
	<boris.ostrovsky@...cle.com>, <david.vrabel@...rix.com>,
	<jbeulich@...e.com>
Subject: Re: [Xen-devel] [PATCH V2 2/3] xen: eliminate scalability issues
 from initrd handling

On 17/09/14 05:12, Juergen Gross wrote:
> Size restrictions native kernels wouldn't have resulted from the initrd
> getting mapped into the initial mapping. The kernel doesn't really need
> the initrd to be mapped, so use infrastructure available in Xen to avoid
> the mapping and hence the restriction.
> 
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
>  arch/x86/xen/enlighten.c | 11 +++++++++--
>  arch/x86/xen/xen-head.S  |  1 +
>  2 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index c0cb11f..8fd075f 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1519,6 +1519,7 @@ static void __init xen_pvh_early_guest_init(void)
>  asmlinkage __visible void __init xen_start_kernel(void)
>  {
>  	struct physdev_set_iopl set_iopl;
> +	unsigned long initrd_start = 0;
>  	int rc;
>  
>  	if (!xen_start_info)
> @@ -1667,10 +1668,16 @@ asmlinkage __visible void __init xen_start_kernel(void)
>  	new_cpu_data.x86_capability[0] = cpuid_edx(1);
>  #endif
>  
> +	if (xen_start_info->mod_start)
> +		initrd_start = __pa(xen_start_info->mod_start);
> +#ifdef CONFIG_BLK_DEV_INITRD
> +	if (xen_start_info->flags & SIF_MOD_START_PFN)
> +		initrd_start = PFN_PHYS(xen_start_info->mod_start);
> +#endif

Why the #ifdef?

I'll fix this up to be:

   if (xen_start_info->mod_start) {
       if (xen_start_info->flags & SIF_MOD_START_PFN)
           initrd_start = PFN_PHYS_(xen_start_info->mod_start);
       else
           initrd_start = __pa(xen_start_info->mod_start);
   }

Unless you object.

David
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