On 2020-02-29 3:47 p.m., Dan Williams wrote: > On Fri, Feb 21, 2020 at 10:25 AM Logan Gunthorpe <logang@xxxxxxxxxxxx> wrote: >> >> PCI BAR IO memory should never be mapped as WB, however prior to this >> the PAT bits were set WB and it was typically overridden by MTRR >> registers set by the firmware. >> >> Set PCI P2PDMA memory to be WC (writecombining) as the only current >> user (the NVMe CMB) was originally mapped WC before the P2PDMA code >> replaced the mapping with devm_memremap_pages(). > > Will the change to UC regress this existing use case? I don't think so. They've been essentially mapped UC for a long time now (since the P2PDMA patch set was merged) and nobody has complained.
