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    SubjectRe: [PATCH 2/3] ACPI, APEI: Add RAM mapping support to ACPI
    +cc Tony, linux-ia64

    On Sat, Jan 21, 2012 at 8:04 AM, Bjorn Helgaas <bhelgaas@google.com> wrote:
    > On Fri, Jan 20, 2012 at 7:13 PM, Myron Stowe <myron.stowe@redhat.com> wrote:
    >> From: Myron Stowe <mstowe@redhat.com>
    >>
    >> This patch adds support for RAM to ACPI's mapping capabilities in order
    >> to support APEI error injection (EINJ) actions.
    >>
    >> This patch re-factors similar functionality introduced in commit
    >> 76da3fb3575, bringing it into osl.c in preparation for removing
    >> ./drivers/acpi/atomicio.[ch].
    >>
    >> Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
    >> ---
    >>
    >>  drivers/acpi/osl.c |   36 ++++++++++++++++++++++++++++++++++--
    >>  1 files changed, 34 insertions(+), 2 deletions(-)
    >>
    >> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
    >> index f363a55..8ee64ea 100644
    >> --- a/drivers/acpi/osl.c
    >> +++ b/drivers/acpi/osl.c
    >> @@ -31,6 +31,7 @@
    >>  #include <linux/kernel.h>
    >>  #include <linux/slab.h>
    >>  #include <linux/mm.h>
    >> +#include <linux/highmem.h>
    >>  #include <linux/pci.h>
    >>  #include <linux/interrupt.h>
    >>  #include <linux/kmod.h>
    >> @@ -321,6 +322,37 @@ acpi_map_lookup_virt(void __iomem *virt, acpi_size size)
    >>        return NULL;
    >>  }
    >>
    >> +#ifndef CONFIG_IA64
    >> +#define should_use_kmap(pfn)   page_is_ram(pfn)
    >> +#else
    >> +/* ioremap will take care of cache attributes */
    >> +#define should_use_kmap(pfn)   0
    >> +#endif
    >> +
    >> +static void __iomem *acpi_map(acpi_physical_address pg_off, unsigned long pg_sz)
    >> +{
    >> +       unsigned long pfn;
    >> +
    >> +       pfn = pg_off >> PAGE_SHIFT;
    >> +       if (should_use_kmap(pfn)) {
    >> +               if (pg_sz > PAGE_SIZE)
    >> +                       return NULL;
    >> +               return (void __iomem __force *)kmap(pfn_to_page(pfn));
    >> +       } else
    >> +               return acpi_os_ioremap(pg_off, pg_sz);
    >
    > This implies that ioremap() works differently on ia64 than on x86.
    > Apparently one can ioremap() RAM on x86, but not on ia64.  Why is this
    > different?  Shouldn't we instead fix ioremap() on ia64 so it works the
    > same as on x86?
    >
    > I looked at the ia64 ioremap(), and I can't see the reason it fails
    > for RAM.  Huang, do you remember the details from 76da3fb3575?
    >
    >> +}
    >> +
    >> +static void acpi_unmap(acpi_physical_address pg_off, void __iomem *vaddr)
    >> +{
    >> +       unsigned long pfn;
    >> +
    >> +       pfn = pg_off >> PAGE_SHIFT;
    >> +       if (page_is_ram(pfn))
    >> +               kunmap(pfn_to_page(pfn));
    >> +       else
    >> +               iounmap(vaddr);
    >
    > I hope we can resolve the ioremap() question so we don't need this
    > patch at all.  But if we do need this, I don't like the asymmetry here
    > -- on x86 RAM, I think we use ioremap() and kunmap(), which seems
    > wrong.  We should be able to use ioremap() and iounmap().
    >
    >> +}
    >> +
    >>  void __iomem *__init_refok
    >>  acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
    >>  {
    >> @@ -353,7 +385,7 @@ acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
    >>
    >>        pg_off = round_down(phys, PAGE_SIZE);
    >>        pg_sz = round_up(phys + size, PAGE_SIZE) - pg_off;
    >> -       virt = acpi_os_ioremap(pg_off, pg_sz);
    >> +       virt = acpi_map(pg_off, pg_sz);
    >>        if (!virt) {
    >>                mutex_unlock(&acpi_ioremap_lock);
    >>                kfree(map);
    >> @@ -384,7 +416,7 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map)
    >>  {
    >>        if (!map->refcount) {
    >>                synchronize_rcu();
    >> -               iounmap(map->virt);
    >> +               acpi_unmap(map->phys, map->virt);
    >>                kfree(map);
    >>        }
    >>  }
    >>
    --
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