Re: [Xen-devel] [PATCH v3 7/8] tools: arm: support up to (almost) 1TB of guest RAM

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes:
> This creates a second bank of RAM starting at 8GB and potentially extending \
to
> the 1TB boundary, which is the limit imposed by our current use of a 3 level
> p2m with 2 pages at level 0 (2^40 bits).
>
> I've deliberately left a gap between the two banks just to exercise those co\
de paths.
> 
> The second bank is 1016GB in size which plus the 3GB below 4GB is 1019GB
> maximum guest RAM. At the point where the fact that this is slightly less th\
an
> a full TB starts to become an issue for people then we can switch to a 4 lev\
el

Your commit messages have wrap damage when quoted.  Can you make your
editor shrink them a bit ?

> -    const uint64_t ram0size = ramsize;
> +    const uint64_t ram0size =
> +        ramsize > GUEST_RAM0_SIZE ? GUEST_RAM0_SIZE : ramsize;
>      const uint64_t ram0end = GUEST_RAM0_BASE + ram0size;
> +    const uint64_t ram1size =
> +        ramsize > ram0size ? ramsize - ram0size : 0;
> +    const uint64_t ram1end = GUEST_RAM1_BASE + ram1size;

Why ram0 and ram1 not ram[0] and ram[1] ?  If the latter

> +    if ((rc = populate_guest_memory(dom,
> +                                    GUEST_RAM1_BASE >> XC_PAGE_SHIFT,
> +                                    ram1size >> XC_PAGE_SHIFT)))
> +        return rc;

this could perhaps be a loop.  (You would need
  const uint64_t guest_ram_size[2] = { GUEST_RAM_SIZES };
or, if you must,
  const uint64_t guest_ram_size[2] = { GUEST_RAM0_SIZE, GUEST_RAM1_SIZE };
or something.)

> +static int make_memory_node(libxl__gc *gc, void *fdt, uint64_t size)
> +{
> +    int res;
> +    /* This had better match libxc's arch_setup_meminit... */
> +    const uint64_t size0 = size > GUEST_RAM0_SIZE ? GUEST_RAM0_SIZE : size;
> +    const uint64_t size1 = size > GUEST_RAM0_SIZE ? size - size0 : 0;

Glrgk.  Is it necessary to have this in two places ?

Ian.

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