kernel.git/arch/powerpc/kernel/io-workarounds.c, branch linux-4.4.y

powerpc/mm: Differentiate between hugetlb and THP during page walk

2015-10-12T04:30:09Z

We need to properly identify whether a hugepage is an explicit or a transparent hugepage in follow_huge_addr(). We used to depend on hugepage shift argument to do that. But in some case that can result in wrong results. For ex: On finding a transparent hugepage we set hugepage shift to PMD_SHIFT. But we can end up clearing the thp pte, via pmdp_huge_get_and_clear. We do prevent reusing the pfn page via the usage of kick_all_cpus_sync(). But that happens after we updated the pte to 0. Hence in follow_huge_addr() we can find hugepage shift set, but transparent huge page check fail for a thp pte. NOTE: We fixed a variant of this race against thp split in commit 691e95fd7396905a38d98919e9c150dbc3ea21a3 ("powerpc/mm/thp: Make page table walk safe against thp split/collapse") Without this patch, we may hit the BUG_ON(flags & FOLL_GET) in follow_page_mask occasionally. In the long term, we may want to switch ppc64 64k page size config to enable CONFIG_ARCH_WANT_GENERAL_HUGETLB Reported-by: David Gibson Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc/mm/thp: Make page table walk safe against thp split/collapse

2015-04-17T01:23:39Z

We can disable a THP split or a hugepage collapse by disabling irq. We do send IPI to all the cpus in the early part of split/collapse, and disabling local irq ensure we don't make progress with split/collapse. If the THP is getting split we return NULL from find_linux_pte_or_hugepte(). For all the current callers it should be ok. We need to be careful if we want to use returned pte_t pointer outside the irq disabled region. W.r.t to THP split, the pfn remains the same, but then a hugepage collapse will result in a pfn change. There are few steps we can take to avoid a hugepage collapse.One way is to take page reference inside the irq disable region. Other option is to take mmap_sem so that a parallel collapse will not happen. We can also disable collapse by taking pmd_lock. Another method used by kvm subsystem is to check whether we had a mmu_notifer update in between using mmu_notifier_retry(). Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc: Better split CONFIG_PPC_INDIRECT_PIO and CONFIG_PPC_INDIRECT_MMIO

2013-08-14T04:57:50Z

Remove the generic PPC_INDIRECT_IO and ensure we only add overhead to the right accessors. IE. If only CONFIG_PPC_INDIRECT_PIO is set, we don't add overhead to all MMIO accessors. Signed-off-by: Benjamin Herrenschmidt

powerpc: Replace find_linux_pte with find_linux_pte_or_hugepte

2013-06-21T06:01:54Z

Replace find_linux_pte with find_linux_pte_or_hugepte and explicitly document why we don't need to handle transparent hugepages at callsites. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Benjamin Herrenschmidt

POWERPC: drivers: remove __dev* attributes.

2013-01-03T23:57:04Z

CONFIG_HOTPLUG is going away as an option. As a result, the __dev* markings need to be removed. This change removes the use of __devinit, __devexit_p, __devinitdata, __devinitconst, and __devexit from these drivers. Based on patches originally written by Bill Pemberton, but redone by me in order to handle some of the coding style issues better, by hand. Cc: Bill Pemberton Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Signed-off-by: Greg Kroah-Hartman

powerpc: io-workarounds.c was implicitly getting init_mm

2011-10-31T23:30:37Z

It was coming in via device.h --> module.h etc. but we want to clean that up. So explicitly include the header where init_mm is being declared. Signed-off-by: Paul Gortmaker

powerpc/pci: Properly initialize IO workaround "private"

2011-04-27T04:18:33Z

Even when no initfunc is provided. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Michael Ellerman Signed-off-by: Benjamin Herrenschmidt

powerpc/pci: Make IO workarounds init implicit when first bus is registered

2011-04-27T04:18:31Z

Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Michael Ellerman Signed-off-by: Benjamin Herrenschmidt

powerpc/pci: Move IO workarounds to the common kernel dir

2011-04-27T04:18:29Z

Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Michael Ellerman Signed-off-by: Benjamin Herrenschmidt