Re: [Xen-devel] RFC: [PATCH 1/3] Enhance platform support for PCI

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.02.15 at 11:09, <mjaggi@xxxxxxxxxxxxxxxxxx> wrote:
> On Monday 23 February 2015 09:50 PM, Jan Beulich wrote:
>>>>> On 23.02.15 at 16:46, <ian.campbell@xxxxxxxxxx> wrote:
>>> On Mon, 2015-02-23 at 15:27 +0000, Jan Beulich wrote:
>>>>>>> On 23.02.15 at 16:02, <ian.campbell@xxxxxxxxxx> wrote:
>>>>> Is the reason for the scan being of segment 0 only is that it is the one
>>>>> which lives at the legacy PCI CFG addresses (or those magic I/O ports)?
>>>> Right - ideally we would scan all segments, but we need Dom0 to
>>>> tell us which MMCFG regions are safe to access,
>>> Is this done via PHYSDEVOP_pci_mmcfg_reserved?
>> Yes.
>>
>>>>   and hence can't
>>>> do that scan at boot time. But we also won't get away without
>>>> scanning, as we need to set up the IOMMU(s) to at least cover
>>>> the devices used for booting the system.
>>> Which hopefully are all segment 0 or aren't needed until after dom0
>>> tells Xen about them I suppose.
>> Right. With EFI one may be able to overcome this one day, but the
>> legacy BIOS doesn't even surface mechanisms (software interrupts)
>> to access devices outside of segment 0.
>>
>>>>   (All devices on segment zero are supposed to
>>>> be accessible via config space access method 1.)
>>> Is that "the legacy ....  or magic ..." again?
>> Yes (just that there are two of them).
> Ian/Jan,
> Have you reached a conclusion?

Regarding what? The context above - at least to me - doesn't make
clear what you refer to.

Jan


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