From: David Gibson <david@gibson.dropbear.id.au>
To: Alexander Graf <agraf@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
mst@redhat.com, eduard.munteanu@linux360.ro,
qemu-devel@nongnu.org, rth@twiddle.net
Subject: Re: [Qemu-devel] [PATCH 10/13] iommu: Introduce IOMMU emulation infrastructure
Date: Wed, 14 Mar 2012 20:05:23 +1100 [thread overview]
Message-ID: <20120314090523.GW24916@truffala.fritz.box> (raw)
In-Reply-To: <FB8C104F-9EFA-4CC2-A0A4-70EB365F9D62@suse.de>
On Tue, Mar 13, 2012 at 03:37:09PM +0100, Alexander Graf wrote:
> On 13.03.2012, at 15:04, David Gibson wrote:
> > On Tue, Mar 13, 2012 at 02:56:47PM +0100, Alexander Graf wrote:
> >> On 13.03.2012, at 06:07, David Gibson wrote:
[snip]
> >>>> This need not be a configure option. Just enable it, or it will
> >>>> bitrot.
> >>>
> >>> I did wonder about that. I'd like to hear that suggested by more than
> >>> one person before I unconditionally add code which will impose an
> >>> overhead on all emulated DMAs.
> >>
> >> Maybe make it a target option? That way targets that want and need
> >> an IOMMU can compile the code in, while the others don't see
> >> performance hits. That would of course mean that we'd still have
> >> conditional code paths, but at least they wouldn't bitrot, as
> >> building multiple targets means you'd build both paths.
> >
> > Heh, yeah, so I tried that way back. It's problematic, unfortunately,
> > as it would require pulling a number of things out of libhw and back
> > into target dependent code.
>
> Hrm. How about measuring the performance overhead then? Maybe it's
> negligible?
Yeah, I should do that. Finding a suitable testcase and running it on
a variety of targets is non-trivial, though.
--
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
next prev parent reply other threads:[~2012-03-14 9:08 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-09 5:01 [Qemu-devel] [0/13] Implement support for guest visible IOMMUs David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 01/13] Use DMADirection type for dma_bdrv_io David Gibson
2012-03-09 9:34 ` Kevin Wolf
2012-03-09 10:01 ` Paolo Bonzini
2012-03-13 5:53 ` David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 02/13] Better support for dma_addr_t variables David Gibson
2012-03-09 10:00 ` Paolo Bonzini
2012-03-09 5:01 ` [Qemu-devel] [PATCH 03/13] usb-xhci: Use PCI DMA helper functions David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 04/13] Implement cpu_physical_memory_zero() David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 05/13] iommu: Add universal DMA helper functions David Gibson
2012-03-09 10:06 ` Paolo Bonzini
2012-03-09 11:19 ` David Gibson
2012-03-09 11:55 ` Paolo Bonzini
2012-03-09 5:01 ` [Qemu-devel] [PATCH 06/13] usb-ohci: Use " David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 07/13] iommu: Make sglists and dma_bdrv helpers use new universal DMA helpers David Gibson
2012-03-09 9:43 ` Kevin Wolf
2012-03-13 10:42 ` David Gibson
2012-03-13 11:55 ` Kevin Wolf
2012-03-09 10:11 ` Paolo Bonzini
2012-03-13 6:37 ` David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 08/13] ide/ahci: Use universal DMA helper functions David Gibson
2012-03-09 9:48 ` Kevin Wolf
2012-03-10 5:30 ` David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 09/13] usb: Convert usb_packet_{map, unmap} to universal DMA helpers David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 10/13] iommu: Introduce IOMMU emulation infrastructure David Gibson
2012-03-09 10:23 ` Paolo Bonzini
2012-03-13 5:07 ` David Gibson
2012-03-13 13:56 ` Alexander Graf
2012-03-13 14:04 ` David Gibson
2012-03-13 14:37 ` Alexander Graf
2012-03-14 9:05 ` David Gibson [this message]
2012-03-09 5:01 ` [Qemu-devel] [PATCH 11/13] pseries: Convert sPAPR TCEs to use generic IOMMU infrastructure David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 12/13] iommu: Allow PCI to use " David Gibson
2012-03-09 5:01 ` [Qemu-devel] [PATCH 13/13] pseries: Implement IOMMU and DMA for PAPR PCI devices David Gibson
2012-03-09 10:23 ` Paolo Bonzini
2012-03-09 10:58 ` David Gibson
2012-03-11 2:02 ` Benjamin Herrenschmidt
-- strict thread matches above, loose matches on Subject: below --
2012-03-22 2:14 [Qemu-devel] [0/13] RFC: Guest visible IOMMU David Gibson
2012-03-22 2:14 ` [Qemu-devel] [PATCH 10/13] iommu: Introduce IOMMU emulation infrastructure David Gibson
2012-03-01 5:35 [Qemu-devel] [0/13] RFC: Support for guest-visible IOMMUs David Gibson
2012-03-01 5:36 ` [Qemu-devel] [PATCH 10/13] iommu: Introduce IOMMU emulation infrastructure David Gibson
2012-03-01 15:49 ` Michael S. Tsirkin
2012-03-02 3:09 ` David Gibson
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