Messages in this thread | | | From | Logan Gunthorpe <> | Date | Thu, 1 Mar 2018 13:57:21 -0700 | Subject | Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory |
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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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