Re: [Xen-ia64-devel] Strange problem with virtual aliases

[Matthew Chapman <matthewc@xxxxxxxxxxxxxxx>]

Anthony,

I realised my mistake... setting the preferred page size to 16MB, meant
that itir.ps = 16MB on a TLB miss, so I was actually inserting 16MB
mappings instead of 4KB mappings.

Thus instead of:
  0x00000000fbdf7000 -> 0x2500000 size 4KB
I was inserting:
  0x00000000fb000000 -> 0x2000000 size 16MB
(hence 0x00000000fbdf7000 -> 0x2df7000)
 
(Other mappings I inserted had the same physical and virtual alignment
so they worked OK.)

tpa returning 0x2500000 is rather strange, though.  I notice that there
is a DTLB miss on the tpa, and then I presume that the entry is obtained
from the 1-entry TLB.  Maybe there is a bug with the mask somewhere.  I
will look at that some more when I have time.

> What's your preferred page size in region 0 and region1?

region 0: was 16MB by mistake, should be 4KB
region 1: 256MB

> You are right, Xen doesn't support mappings whose page size < 16K,
> Xen will insert this smaller mapping into VHPT assuming  it is 16k page size.

I have compiled Xen with 4KB base page size (CONFIG_IA64_PAGE_SIZE_4KB in
xen/include/asm-ia64/config.h), so PAGE_SHIFT=12.  It seems to work, but
of course it's possible that some code still assumes 16KB.

Matt

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