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    SubjectRe: [PATCH 2/3] ACPI, APEI: Add RAM mapping support to ACPI
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    On Sat, 2012-01-21 at 08:04 -0700, Bjorn Helgaas 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().

    Huang:

    There seems to be a lot of people wondering about this - could you
    respond please.

    Myron
    >
    > > +}
    > > +
    > > 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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