Re: [PATCH 2/3] ACPI, APEI: Add RAM mapping support to ACPI

Bjorn Helgaas
2012-01-21T20:38:53Z

+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);
>>        }
>>  }
>>