1. 06 Sep, 2018 1 commit
    • Paul Burton's avatar
      MIPS: Fix ioremap() RAM check · 31c5526e
      Paul Burton authored
      BugLink: https://bugs.launchpad.net/bugs/1790620
      
      commit 523402fa upstream.
      
      We currently attempt to check whether a physical address range provided
      to __ioremap() may be in use by the page allocator by examining the
      value of PageReserved for each page in the region - lowmem pages not
      marked reserved are presumed to be in use by the page allocator, and
      requests to ioremap them fail.
      
      The way we check this has been broken since commit 92923ca3 ("mm:
      meminit: only set page reserved in the memblock region"), because
      memblock will typically not have any knowledge of non-RAM pages and
      therefore those pages will not have the PageReserved flag set. Thus when
      we attempt to ioremap a region outside of RAM we incorrectly fail
      believing that the region is RAM that may be in use.
      
      In most cases ioremap() on MIPS will take a fast-path to use the
      unmapped kseg1 or xkphys virtual address spaces and never hit this path,
      so the only way to hit it is for a MIPS32 system to attempt to ioremap()
      an address range in lowmem with flags other than _CACHE_UNCACHED.
      Perhaps the most straightforward way to do this is using
      ioremap_uncached_accelerated(), which is how the problem was discovered.
      
      Fix this by making use of walk_system_ram_range() to test the address
      range provided to __ioremap() against only RAM pages, rather than all
      lowmem pages. This means that if we have a lowmem I/O region, which is
      very common for MIPS systems, we're free to ioremap() address ranges
      within it. A nice bonus is that the test is no longer limited to lowmem.
      
      The approach here matches the way x86 performed the same test after
      commit c81c8a1e ("x86, ioremap: Speed up check for RAM pages") until
      x86 moved towards a slightly more complicated check using walk_mem_res()
      for unrelated reasons with commit 0e4c12b4 ("x86/mm, resource: Use
      PAGE_KERNEL protection for ioremap of memory pages").
      Signed-off-by: default avatarPaul Burton <paul.burton@mips.com>
      Reported-by: default avatarSerge Semin <fancer.lancer@gmail.com>
      Tested-by: default avatarSerge Semin <fancer.lancer@gmail.com>
      Fixes: 92923ca3 ("mm: meminit: only set page reserved in the memblock region")
      Cc: James Hogan <jhogan@kernel.org>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: linux-mips@linux-mips.org
      Cc: stable@vger.kernel.org # v4.2+
      Patchwork: https://patchwork.linux-mips.org/patch/19786/Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      Signed-off-by: default avatarStefan Bader <stefan.bader@canonical.com>
      Signed-off-by: default avatarKleber Sacilotto de Souza <kleber.souza@canonical.com>
      31c5526e
  2. 05 Sep, 2018 5 commits
  3. 04 Sep, 2018 3 commits
  4. 27 Aug, 2018 13 commits
  5. 15 Aug, 2018 1 commit
  6. 14 Aug, 2018 17 commits