Re: [Qemu-ppc] [Qemu-devel] KVM call minutes 2013-01-29 - Port I/O

[Alex Williamson]

On Thu, 2013-01-31 at 10:02 +1100, Benjamin Herrenschmidt wrote:
> On Thu, 2013-01-31 at 00:49 +0200, Michael S. Tsirkin wrote:
> > > In practice they do (VGA at least)
> > > 
> > > >From a SW modelling standpoint, I don't think it's worth
> > differentiating
> > > PCI and PCIE.
> > > 
> > > Cheers,
> > > Ben.
> > 
> > Interesting.
> > Do you have such hardware? Could you please dump
> > the output of lspci -vv?
> 
> Any ATI or nVidia card still supports hard decoding of VGA regions for
> the sake of legacy operating systems and BIOSes :-) I don't know about
> Intel but I suppose it's the same.

For example:

-[0000:00]-+-00.0  Advanced Micro Devices [AMD] nee ATI RD890 PCI to PCI bridge 
(external gfx0 p
           +-04.0-[02]--+-00.0  Advanced Micro Devices [AMD] nee ATI Cedar PRO 
[Radeon HD 5450/6350]

00:04.0 PCI bridge: Advanced Micro Devices [AMD] nee ATI RD890 PCI to PCI 
bridge (PCI express gpp port D) (prog-if 00 [Normal decode])
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- 
Stepping- SERR- FastB2B- DisINTx-
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort- >SERR- <PERR- INTx-
        Latency: 0, Cache Line Size: 64 bytes
        Bus: primary=00, secondary=02, subordinate=02, sec-latency=0
        I/O behind bridge: 0000c000-0000cfff
        Memory behind bridge: fd100000-fd1fffff
        Prefetchable memory behind bridge: 00000000d0000000-00000000dfffffff
        Secondary status: 66MHz- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- 
<MAbort+ <SERR- <PERR-
        BridgeCtl: Parity- SERR- NoISA- VGA+ MAbort- >Reset- FastB2B-
                                      ^^^^

VGA+ (VGA Enable) indicates positive decode of 0x3b0 - 0x3bb, 0x3c0 -
0x3df, and 0xa0000 - 0xbfff.  Device 2:00.0 of course doesn't report
these "ISA" ranges as they're implicit in the VGA class code.

BTW, I've been working on vfio-pci support of VGA assignment which makes
use of the VGA arbiter in the host to manipulate the VGA Enable control
register, allowing us to select which device to access.  The qemu side
is simply registering memory regions for the VGA areas and expecting to
be used with -vga none, but I'll adopt whatever strategy we choose for
hard coded address range support.  Current base patches at the links
below.  Thanks,

Alex

https://github.com/awilliam/qemu-vfio/commit/ea2befa59010a429dcf13c10dbccdf8b64e82fbd
https://github.com/awilliam/linux-vfio/commit/bae182d929229cbf1eaeb01e5fad4f77f81a4c61