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Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI hos
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges |
Date: |
Wed, 21 Nov 2012 15:13:39 +0200 |
On Wed, Nov 21, 2012 at 11:36:00PM +1100, David Gibson wrote:
> On Wed, Nov 21, 2012 at 01:34:48PM +0200, Michael S. Tsirkin wrote:
> > On Wed, Nov 21, 2012 at 11:57:05AM +1100, David Gibson wrote:
> > > On Tue, Nov 20, 2012 at 02:26:09PM +0200, Michael S. Tsirkin wrote:
> > > > On Tue, Nov 20, 2012 at 10:27:11AM +0100, Alexander Graf wrote:
> > > > >
> > > > > On 19.11.2012, at 23:51, David Gibson wrote:
> > > > >
> > > > > > On Mon, Nov 19, 2012 at 05:34:12PM +0100, Alexander Graf wrote:
> > > > > >>
> > > > > >> On 13.11.2012, at 03:47, David Gibson wrote:
> > > > > >>
> > > > > >>> From: Alexey Kardashevskiy <address@hidden>
> > > > > >>>
> > > > > >>> In future (with VFIO) we will have multiple PCI host bridges on
> > > > > >>> pseries. Each one needs a unique LIOBN (IOMMU id). At the
> > > > > >>> moment we
> > > > > >>> derive these from the pci domain number, but the whole notion of
> > > > > >>> domain numbers on the qemu side is bogus and in any case they're
> > > > > >>> not
> > > > > >>> actually uniquely allocated at this point.
> > > > > >>>
> > > > > >>> This patch, therefore uses a simple sequence counter to generate
> > > > > >>> unique LIOBNs for PCI host bridges.
> > > > > >>>
> > > > > >>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> > > > > >>> Signed-off-by: David Gibson <address@hidden>
> > > > > >>
> > > > > >> I don't really like the idea of having a global variable just
> > > > > >> because our domain ID generation seems to not work as
> > > > > >> expected. Michael, any comments here?
> > > > > >
> > > > > > Well, the patch I sent which changed domain id generation was
> > > > > > ignored. In any case, as I said, the whole concept of domain
> > > > > > numbers
> > > > >
> > > > > Michael?
> > > >
> > > > This is user visible, right?
> > > > So IMHO we should have the user specify LIOBN through a property,
> > > > rather than assign what's essentially a random value.
> > >
> > > Well, I can implement an override through a property, which could be
> > > useful in some circumstances. But we still need to have qemu generate
> > > unique defaults, rather than forcing it to be specified in every case.
> >
> > I don't see why.
> > And if you want automatic defaults then they need to be generated in a
> > way that does not depend on implementation detail such as order of
> > device initialization.
>
> Because requiring explicit unique liobns to be supplied whenever there
> is more than one PHB is horrible for usability.
We should make simple things simple and complex things possible.
More than one PHB seems like an advanced feature
so I don't see why it needs to be made very easy to use.
With an appropriate error message it should not be
too hard for users to figure it out.
> --
> 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
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 08/12] target-ppc: Convert ppcemb_tlb_t to use fixed 64-bit RPN, (continued)
- [Qemu-ppc] [PATCH 07/12] pseries: Split xics irq configuration from state information, David Gibson, 2012/11/12
- [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/12
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Alexander Graf, 2012/11/19
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/19
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Alexander Graf, 2012/11/20
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Michael S. Tsirkin, 2012/11/20
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/20
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Michael S. Tsirkin, 2012/11/21
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/21
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges,
Michael S. Tsirkin <=
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/21
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Alexander Graf, 2012/11/21
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Michael S. Tsirkin, 2012/11/21
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/21
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Michael S. Tsirkin, 2012/11/22
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Alexander Graf, 2012/11/22
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Michael S. Tsirkin, 2012/11/22
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/22
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, Michael S. Tsirkin, 2012/11/23
- Re: [Qemu-ppc] [PATCH 12/12] pseries: Generate unique LIOBNs for PCI host bridges, David Gibson, 2012/11/23