Re: [PATCH] x86/iommu: account for necessary allocations when calculating Dom0's initial allocation size

[Keir Fraser <keir@xen.org>]

Thank Jan. I'm not really sure about putting your earlier patch into 4.0.2,
so can I put only this patch in for 4.0.2, replacing max_pdx with max_page?

 -- Keir

On 14/12/2010 09:03, "Jan Beulich" <JBeulich@novell.com> wrote:

> As of c/s 21812:e382656e4dcc, IOMMU related allocations for Dom0
> happen only after it got all of its memory allocated, and hence the
> reserve (mainly for setting up its swiotlb) may get exhausted without
> accounting for the necessary allocations up front.
> 
> While not precise, the estimate has been found to be within a couple
> of pages for the systems it got tested on.
> 
> For the calculation to be reasonably correct, this depends on the
> patch titled "x86/iommu: don't map RAM holes above 4G" sent out
> yesterday.
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> 
> --- a/xen/arch/x86/domain_build.c
> +++ b/xen/arch/x86/domain_build.c
> @@ -191,6 +191,15 @@ static unsigned long __init compute_dom0
>      if ( is_pv_32on64_domain(d) )
>          avail -= opt_dom0_max_vcpus - 1;
>  
> +    /* Reserve memory for iommu_dom0_init() (rough estimate). */
> +    if ( iommu_enabled )
> +    {
> +        unsigned int s;
> +
> +        for ( s = 9; s < BITS_PER_LONG; s += 9 )
> +            avail -= max_pdx >> s;
> +    }
> +
>      /*
>       * If domain 0 allocation isn't specified, reserve 1/16th of available
>       * memory for things like DMA buffers. This reservation is clamped to
> 
> 
> 
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