Re: [Xen-devel] [PATCH 7/7] xen: Convert __page_to_mfn and __mfn_to_page to use typesafe MFN

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.10.17 at 01:27, <andrew.cooper3@xxxxxxxxxx> wrote:
> As for TMEM itself (Julien: This my no means blocks the patch.  It is
> more an observation for Konrad to see about fixing), I see that TMEM is
> broken on x86 machines with more than 5TB of RAM, because it is not
> legal to call page_to_virt() on a struct page_info allocated from the
> domheap (which is why alloc_xenheap_page() returns a void *, and
> alloc_domheap_page() specifically doesn't).  The easy fix for this is to
> swap the allocation primitives over to using xenheap allocations, which
> would remove the need for page_to_virt() and back, or a better fix would
> be to not pass everything thing by virtual address (at which point
> retaining use of the domheap is fine).

For this reason we have

        if ( tmem_enabled() )
        {
           printk(XENLOG_WARNING
                  "TMEM physical RAM limit exceeded, disabling TMEM\n");
           tmem_disable();
        }

in setup.c.

Jan


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