• Logan Gunthorpe's avatar
    mm/memory_hotplug: drop the flags field from struct mhp_restrictions · 96c6b598
    Logan Gunthorpe authored
    Patch series "Allow setting caching mode in arch_add_memory() for
    P2PDMA", v4.
    
    Currently, the page tables created using memremap_pages() are always
    created with the PAGE_KERNEL cacheing mode.  However, the P2PDMA code is
    creating pages for PCI BAR memory which should never be accessed through
    the cache and instead use either WC or UC.  This still works in most
    cases, on x86, because the MTRR registers typically override the caching
    settings in the page tables for all of the IO memory to be UC-.
    However, this tends not to work so well on other arches or some rare x86
    machines that have firmware which does not setup the MTRR registers in
    this way.
    
    Instead of this, this series proposes a change to arch_add_memory() to
    take the pgprot required by the mapping which allows us to explicitly
    set pagetable entries for P2PDMA memory to UC.
    
    This changes is pretty routine for most of the arches: x86_64, arm64 and
    powerpc simply need to thread the pgprot through to where the page
    tables are setup.  x86_32 unfortunately sets up the page tables at boot
    so must use _set_memory_prot() to change their caching mode.  ia64, s390
    and sh don't appear to have an easy way to change the page tables so,
    for now at least, we just return -EINVAL on such mappings and thus they
    will not support P2PDMA memory until the work for this is done.  This
    should be fine as they don't yet support ZONE_DEVICE.
    
    This patch (of 7):
    
    This variable is not used anywhere and should therefore be removed from
    the structure.
    Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
    Reviewed-by: default avatarDan Williams <dan.j.williams@intel.com>
    Acked-by: default avatarMichal Hocko <mhocko@suse.com>
    Cc: Christoph Hellwig <hch@lst.de>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Will Deacon <will@kernel.org>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Eric Badger <ebadger@gigaio.com>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: Jason Gunthorpe <jgg@ziepe.ca>
    Cc: Michael Ellerman <mpe@ellerman.id.au>
    Cc: Paul Mackerras <paulus@samba.org>
    Link: http://lkml.kernel.org/r/20200306170846.9333-2-logang@deltatee.comSigned-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    96c6b598
memory_hotplug.h 11 KB