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Re: [Qemu-devel] [RFC v5 0/6] pci_expander_brdige: support separate pci

From: Zihan Yang
Subject: Re: [Qemu-devel] [RFC v5 0/6] pci_expander_brdige: support separate pci domain for pxb-pcie
Date: Thu, 20 Sep 2018 10:30:58 +0800

Gerd Hoffmann <address@hidden> 于2018年9月19日周三 下午12:26写道:
> > > > 2. Only 4x devices is supported, you need to be careful not to overuse
> > >
> > > Could you elaborate on this please? What happens if you are not careful?
> > > How does management know what the limits are?
> >
> > It means the user might use more space than 768MB for mmconfig,
> > which is [0x80000000m 0xb0000000). If such situation happens,  seabios
> > will ignore all extra pxb-pcie devices and not adding e820 entry for them,
> > which makes all the devices under them unworkable.
> Ypu should clearly note that this is a limitation of the seabios support
> patches then, so not an issue of the qemu patches.

OK, description will be clearer in next version.

> > As for the management, will some checks when adding mcfg be enough for
> > management? Or I can maintain a variable to indicate how many space
> > have been consumed and warn the user if they exceed the threshold?
> > The latter allows us to do the check when the pxb-pcie is initializing.
> I think qemu should not apply any restrictions here.

But will that confuse users when their device is not listed in guest os
while qemu does not throw any error/warning?

> cheers,
>   Gerd


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