Re: [Xen-devel] [PATCH] acpi: Switch to dynamic mapping at SYS_STATE_boot

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 01/31/2017 06:01 AM, Jan Beulich wrote:
>>>> On 30.01.17 at 19:26, <boris.ostrovsky@xxxxxxxxxx> wrote:
>> We can switch ACPI from using fixmap to dynamic mapping as soon as
>> the system enters SYS_STATE_boot. This will allow us, for example,
>> to map MADT on systems with large number of processors where the
>> table might not fit into NUM_FIXMAP_ACPI_PAGES (currently set to 4).
> I think this needs a little more care. While ARM switches to
> SYS_STATE_boot after having called vm_init(), that's not the case
> on x86. Granted there's no ACPI code being invoked in between,
> but this would still be a latent bug (as soon as someone inserts any
> code there).

Then acpi_os_map_memory() shouldn't rely on system_state at all.

How about adding something like

static bool_t vm_ready()
{
    return !!vm_base[VMAP_DEFAULT];
}

-boris


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