[Xen-devel] c/s 24425:053a44894279 (xsm: add checks on PCI configuration access)

["Jan Beulich" <JBeulich@xxxxxxxx>]

The mmconfig part of this is seriously broken: These operations,
even when carried out by Dom0, are MMIO accesses, and hence
are invisible to the hypervisor without extra handling. Putting
the checks into pci_mmcfg_{read,write}() has the effect of
potentially denying the _hypervisor_ access. So I think at least
that part needs to be reverted.

Even the I/O port base logic isn't fully correct - AMD's extension
to access extended config space isn't being taken care of (i.e.
wrong register values might get passed to the xsm callback).

(It is, btw, also this c/s that prompted the fix titled "x86/PCI:
fix guest_io_read() when pci_cfg_ok() denies access" I sent
out earlier today, so if we decide to revert the whole c/s, that
wouldn't be needed anymore. Yet the function comes handy
for dealing with the MMIO-write-masking that we're currently
evaluating with the AMD folks to get their IOMMU interrupts
working again with recent Linux Dom0 - see yesterday's
http://lists.xen.org/archives/html/xen-devel/2012-06/msg01129.html.)

Jan


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