On 01/03/18 01:53 PM, Jason Gunthorpe wrote:
On Fri, Mar 02, 2018 at 07:40:15AM +1100, Benjamin Herrenschmidt wrote:
Also we need to be able to hard block MEMREMAP_WB mappings of non-RAM
on ppc64 (maybe via an arch hook as it might depend on the processor
family). Server powerpc cannot do cachable accesses on IO memory
(unless it's special OpenCAPI or nVlink, but not on PCIe).
I think you are right on this - even on x86 we must not create
cachable mappings of PCI BARs - there is no way that works the way
anyone would expect.
On x86, even if I try to make a cachable mapping of a PCI BAR it always
ends up being un-cached. The arch code in x86 always does the right
thing here.... Other arches, not so much.
Logan
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