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When the debugpat kernel boot flag is turned on the following traces are printed: [ 1884.793168] x86/PAT: Overlap at 0x90000000-0x92000000 [ 1884.803510] x86/PAT: reserve_memtype added [mem 0x91200000-0x9127ffff], track uncached-minus, req write-combining, ret uncached-minus [ 1884.818167] hfi1 0000:05:00.0: hfi1_0: WC Remapped RcvArray: ffffc9000a980000 The ioremap_wc() clearly is not returning a write combining mapping due to an overlap where the RcvArray is mapped in a uncached mapping prior to creating the proposed write combining mapping. The patch replaces the single base register for uncached CSRs that used to overlap the RcvArray with two mappings. One, kregbase1, from the bar0 up to the RcvArray and another, kregbase2, from the end of the RcvArray to the pio send buffer space. A new dd field, base2_start, is used to convert the zero-based offset in the CSR routines to the correct kregbase1/kregbase2 mapping. A single direct write of the RcvArray CSRs is replaced with hfi1_put_tid() to insure correct access using the new disjoint mapping. Additionally, the kregend field is deleted since it is only ever written. patdebug now shows the RcvArray as write combining: [ 35.688990] x86/PAT: reserve_memtype added [mem 0x91200000-0x9127ffff], track write-combining, req write-combining, ret write-combining To insulate from any potential issues with write combining, all writeq are now flushed in hfi1_put_tid() and rcv_array_wc_fill(). Reviewed-by: Mitko Haralanov <mitko.haralanov@intel.com> Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com> Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.