Re: [Xen-devel] Consuming PCI device in PV kernel

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-07-25 at 13:56 +0100, Simon Martin wrote:
> Hello Ian,
> 
> > IIRC from the guest PoV you just need to read the BAR values from the
> > CFG space and then use them without worrying about where they point,
> > i.e. by creating virtual address mappings of whatever MMIO address the
> > BAR gives you.
> 
> I  thought that I was mapping the BAR memory correctly, however when I
> fixed  a  bug in my software I started getting errors and I eventually
> tracked it down to mapping the MMIO memory.
> 
> I     have     tried     calling    HYPERCALL_update_va_mapping    and
> HYPERCALL_mmu_update  and  they both fail. HYPERCALL_update_va_mapping
> gives me the following in xl dmesg:
> 
> (XEN) mm.c:1700:d292v0 Bad L1 flags 400000
> 
> Looking at the code I can't see where bit 22 is being set!

Without seeing you code I've no idea about this (even if I could see it,
I dunno...)

> Reading  the qemu PCI mapping code, it seems to call xc_domctl. I have
> traced   down   through  this  into  the xen source and it seems to do
> many  things that I don't have access to via straight hypercalls.

domctl's are not for normal guest use.

So this is probably Qemu doing device model things. For a PV domain
either the toolstack has already done them, or they don't need doing or
they are something you do yourself via a different interface.

Ian.


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