Re: [Xen-devel] [PATCH] libxc: x86: ensure that the initial mapping fits into the guest's memory

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-01-07 at 11:05 +0000, Jan Beulich wrote:
> >>  The 4.1.3 xl doesn't really want to work
> >> for me, so I can't directly cross check whether there's a behavioral
> >> difference between the two, but looking at an older log the virtual
> >> addresses reported for virt_alloc_end look similar. Afaict you need
> >> to subtract dom->parms.virt_base from try_virt_end.
> > 
> > I bet virt_base == 0 for the mini-os kernel I tried. I'll respin and
> > retest.
> 
> This is what works for me (also added printing of the relevant value,
> and dropping the unchanged parts of the patch):

This looks sensible to me, thanks. I shall respin the complete patch
shortly.

Ian.

> 
> --- a/tools/libxc/xc_dom_x86.c
> +++ b/tools/libxc/xc_dom_x86.c
> @@ -82,6 +82,7 @@ static int count_pgtables(struct xc_dom_
>  {
>      int pages, extra_pages;
>      xen_vaddr_t try_virt_end;
> +    xen_pfn_t try_pfn_end;
>  
>      extra_pages = dom->alloc_bootstack ? 1 : 0;
>      extra_pages += dom->extra_pages;
> @@ -91,6 +92,16 @@ static int count_pgtables(struct xc_dom_
>      {
>          try_virt_end = round_up(dom->virt_alloc_end + pages * PAGE_SIZE_X86,
>                                  bits_to_mask(22)); /* 4MB alignment */
> +        try_pfn_end = (try_virt_end - dom->parms.virt_base) >> 
> PAGE_SHIFT_X86;
> +
> +        if ( try_pfn_end > dom->total_pages )
> +        {
> +            xc_dom_panic(dom->xch, XC_OUT_OF_MEMORY,
> +                         "%s: not enough memory for initial mapping 
> (%#"PRIpfn" > %#"PRIpfn")",
> +                         __FUNCTION__, try_pfn_end, dom->total_pages);
> +            return -ENOMEM;
> +        }
> +
>          dom->pg_l4 =
>              nr_page_tables(dom, dom->parms.virt_base, try_virt_end, l4_bits);
>          dom->pg_l3 =
> 
> Jan
> 



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