Re: [RFC PATCH 0/3] generic hypercall support

Chris Wright
2009-05-07T21:58:49Z

* Gregory Haskins (gregory.haskins@gmail.com) wrote:
> Arnd Bergmann wrote:
> > pci_iomap could look at the bus device that the PCI function sits on.
> > If it detects a PCI bridge that has a certain property (config space
> > setting, vendor/device ID, ...), it assumes that the device itself
> > will be emulated and it should set the address flag for IO_COND.
> >
> > This implies that all pass-through devices need to be on a different
> > PCI bridge from the emulated devices, which should be fairly
> > straightforward to enforce.

Hmm, this gets to the grey area of the ABI. I think this would mean an
upgrade of the host would suddenly break when the mgmt tool does:

(qemu) pci_add pci_addr=0:6 host host=01:10.0

> Thats actually a pretty good idea.
>
> Chris, is that issue with the non ioread/iowrite access of a mangled
> pointer still an issue here? I would think so, but I am a bit fuzzy on
> whether there is still an issue of non-wrapped MMIO ever occuring.

Arnd was saying it's a bug for other reasons, so perhaps it would work
out fine.

thanks,
-chris