Re: [Xen-devel] ACPI fixmap overflow

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/11/2016 20:39, Boris Ostrovsky wrote:
> On 11/15/2016 02:45 PM, Andrew Cooper wrote:
>> On 15/11/16 19:34, Boris Ostrovsky wrote:
>>> In addition to running out of e820 entries on that large machine that
>>> Alex was referring to in [0] he is also running out of ACPI fixmap space
>>> while parsing MADT (the box has *lots* of processors). The
>>> quick-and-dirty solution is to increase NUM_FIXMAP_ACPI_PAGES but I
>>> wonder whether we should move to dynamic memory allocation.
>> Why do we use fixmap anyway?  It doesn't look too hard to reorder
>> vm_init() slightly higher, and be able to use ioremap() for all APCI tables.
> Hmm... Let me see how possible this is. Just moving it up won't work
> since heap allocator is initialized after ACPI tables.

We have plenty of usable PTEs already allocated at boot, mainly from the
init pagetables.  Given a static __init vm_bitmap, a new boot-time-only
vm range should be usable without any heap allocations at all.

~Andrew

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