On Mon, Jun 19, 2017 at 12:32:48PM +0200, Thomas Huth wrote: > On 19.06.2017 11:39, Alexander Graf wrote: > > On 06/15/2017 03:33 PM, Peter Maydell wrote: > >> I've just noticed that on a SPARC host, some of the PPC guests > >> warn during make check: > >> > >> /ppc64/prom-env/pseries: > >> qemu-system-ppc64: System page size 0x2000 is not enabled in > >> page_size_mask (0x11000). Performance may be slow > >> > >> Is this really a performance problem on a TCG guest? > >> It makes the 'make check' output a bit noisy, but not > >> unbearably so. > > > > From what I can tell this really only affects DDW which should be page > > size agnostic when only using emulated devices. Maybe Alexey thought of > > using VFIO-pci devices in a TCG guest? > > Maybe we could at least silence the warning by checking > qtest_enabled()?
So,
1) Yes, we should at least silence the warning.
2) Certainly the mentioned slowdown shouldn't be significant for TCG
guests.
3) I _think_ the restriction which causes the slowdown doesn't even
exist for TCG, but I haven't 100% convinced myself of this. I've been
sick lately, so my brain isn't working all that well.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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