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

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 01/31/2017 10:56 AM, Jan Beulich wrote:
>>>> On 31.01.17 at 16:52, <boris.ostrovsky@xxxxxxxxxx> wrote:
>> 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.
> Why?

Because it really is only interested in whether vm_init() has been
called, nor what the overall system state is (even if vmap status can be
implied from the state).

But I can swap the two if you prefer that.

-boris

>
>> How about adding something like
>>
>> static bool_t vm_ready()
>> {
>>     return !!vm_base[VMAP_DEFAULT];
>> }
> What's wrong with just swapping the order of the two things in
> x86's setup.c?

I


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