Re: 2.6.25-rc1 xen pvops regression

Ian Campbell
2008-02-21T22:13:33Z

On Thu, 2008-02-21 at 13:37 -0800, Jeremy Fitzhardinge wrote:
> H. Peter Anvin wrote:
> >> Still curious about why a pagetable page is ending up in that range
> >> though. Seems like it shouldn't be possible, since we shouldn't be
> >> allowed to allocate from those pages, at least until the DMI probe
> >> has happened... Unless the early allocator is only excluded from
> >> e820 reserved pages, which would cause a problem on systems which
> >> don't reserve the DMI space... HPA?
> >>
> >
> > I thought the problem was a Xen-provided pagetable from before Linux
> > started?
>
> Hm, I don't think so. The domain-builder pagetable is put after the
> kernel, so it shouldn't be under 1M.

I can confirm that it is Linux which is allocating it. The call path:
# xm create -c debian-x86_32p-1
Using config file "/etc/xen/debian-x86_32p-1".
Started domain debian-1
xen_alloc_pt_init PFN f0
Pid: 0, comm: swapper Not tainted 2.6.25-rc2 #68
[<c02ecb6b>] xen_alloc_pt_init+0x4b/0x60
[<c02f5e2b>] one_page_table_init+0x8b/0xf0
[<c02f63df>] paging_init+0x3bf/0x520
[<c02ee444>] setup_arch+0x2a4/0x410
[<c02e9a64>] start_kernel+0x64/0x380
[<c02efd7f>] cpu_detect+0x6f/0xf0
[<c02ed1a1>] xen_start_kernel+0x2f1/0x310
=======================
Entering add_active_range(0, 0, 262144) 0 entries of 256 used
Zone PFN ranges:
DMA 0 -> 4096

Ian.
>
> J
>
--
Ian Campbell

Why do they call a fast a fast, when it goes so slow?