Hi Peter,
On Fri, Oct 14, 2016 at 02:23:55PM +0800, Peter Xu wrote:
> On Thu, Oct 13, 2016 at 04:16:03PM +0200, Alexander Gordeev wrote:
> > On Thu, Oct 13, 2016 at 02:40:35PM +0800, Peter Xu wrote:
> > > > > > + return pci_translate_addr(dev, addr);
> > > > >
> > > > > Raw question: do we need to translate bar addresses as well?
> > > >
> > > > I believe, yes.
> > > >
> > > > Unless we always have identity mapping between PCI address space and
> > > > CPU physical address space I can not realize how could it be done
> > > > otherwise. But even if we were, I would leave the translation routine
> > > > for clarity.
> > >
> > > Sorry I didn't quite catch your point. Are we talking about IOMMU
> > > address remapping here? IMHO BAR addresses are from CPU's point of
> > > view. It's only used by CPU, not device. In that case, BAR address
> > > should not be translated at least by IOMMU (no matter for x86/arm or
> > > whatever).
> > >
> > > Take Linux as example: pci_ioremap_bar() is responsible to be called
> > > for any PCI drivers to map device memory bars into kernel virtual
> > > address space. Basically it does:
> > >
> > > void __iomem *pci_ioremap_bar(struct pci_dev *pdev, int bar)
> > > {
> > > struct resource *res = &pdev->resource[bar];
> > > return ioremap_nocache(res->start, resource_size(res));
> > > }
> > >
> > > So as it is written: I believe we don't translate the bar address
> > > (which should be res->start). We use it as physical address.
> > >
> > > Or, do you mean other kinds of translation that I don't aware of?
> >
> > Yes, I mean translation from PCI bus address space to CPU physical
> > address space. These two busses are different and hence need a
> > translation. I assume Linux pci_dev::resource[] have translated
> > address, but it is not what PCI devices see. Unless I do not terribly
> > missing somethig, BAR addresses is what a device sees on its AD[0..31]
> > pins.
>
> I believe pci_dev::resource[] should be assigned by BIOS or something
> before Linux. At that time, IOMMU is possibly even not inited. So no
> chance for a translation at all.
kvm-unit-tests != Linux
kvm-unit-tests/arm doesn't have a bootloader at all (not counting QEMU
initializing registers, and a handful of QEMU generated instructions
that gives us a kick)
Anyway, I'm glad you're reviewing this series (my PCI skills are
minimal), but you'll have to review it in the right context. In
this case, more of a seabios context.
Thanks,
drew
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
