[PATCH] ACPI: Fix logic for removing mappings in 'acpi_unmap'

[PATCH] ACPI: Fix logic for removing mappings in 'acpi_unmap'

[Myron Stowe]

From: Myron Stowe <mstowe@redhat.com>

Make sure the removal of mappings uses the same logic that put the
mappings in place.

Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
---

 drivers/acpi/osl.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 412a1e0..5aef087 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -347,7 +347,7 @@ 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))
+	if (should_use_kmap(pfn))
 		kunmap(pfn_to_page(pfn));
 	else
 		iounmap(vaddr);

Re: [PATCH] ACPI: Fix logic for removing mappings in 'acpi_unmap'

[Bjorn Helgaas]

On Thu, Feb 9, 2012 at 8:36 AM, Myron Stowe <myron.stowe@redhat.com> wrote:
> From: Myron Stowe <mstowe@redhat.com>
>
> Make sure the removal of mappings uses the same logic that put the
> mappings in place.
>
> Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
> ---
>
>  drivers/acpi/osl.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 412a1e0..5aef087 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -347,7 +347,7 @@ 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))
> +       if (should_use_kmap(pfn))
>                kunmap(pfn_to_page(pfn));
>        else
>                iounmap(vaddr);
>

Whatever happened to the question of why we have arch-specific
ioremap() behavior?  It's good to make map/unmap symmetric, but it'd
be better to get rid of the ioremap/kmap hack.

Bjorn

Re: [PATCH] ACPI: Fix logic for removing mappings in 'acpi_unmap'

[Myron Stowe]

On Thu, 2012-02-09 at 08:42 -0800, Bjorn Helgaas wrote:
> On Thu, Feb 9, 2012 at 8:36 AM, Myron Stowe <myron.stowe@redhat.com> wrote:
> > From: Myron Stowe <mstowe@redhat.com>
> >
> > Make sure the removal of mappings uses the same logic that put the
> > mappings in place.
> >
> > Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
> > ---
> >
> >  drivers/acpi/osl.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> > index 412a1e0..5aef087 100644
> > --- a/drivers/acpi/osl.c
> > +++ b/drivers/acpi/osl.c
> > @@ -347,7 +347,7 @@ 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))
> > +       if (should_use_kmap(pfn))
> >                kunmap(pfn_to_page(pfn));
> >        else
> >                iounmap(vaddr);
> >
> 
> Whatever happened to the question of why we have arch-specific
> ioremap() behavior?  It's good to make map/unmap symmetric, but it'd
> be better to get rid of the ioremap/kmap hack.

+cc ingo

We never received any explanation for why ioremap() failed for Ying with
RAM on x86.  Last I saw Ying asked Ingo for some input here but there
was never any reply -
http://marc.info/?l=linux-acpi&m=132788392604738&w=2

I like your idea of possibly changing ioremap's implementation so that
it would handle requests related to RAM - by using kmap() internally
when necessary - so that a *user* wouldn't need to care what
architecture we're on.  I, however, feel like I don't have enough
experience with the memory management subsystem to know if such a tactic
would fly or not so was uncomfortable proceeding along those lines.  As
a result, I just wanted to get this in for the meantime.

Myron

> 
> Bjorn

Re: [PATCH] ACPI: Fix logic for removing mappings in 'acpi_unmap'

[Bjorn Helgaas]

On Thu, Feb 9, 2012 at 4:08 PM, Myron Stowe <mstowe@redhat.com> wrote:
> On Thu, 2012-02-09 at 08:42 -0800, Bjorn Helgaas wrote:
>> On Thu, Feb 9, 2012 at 8:36 AM, Myron Stowe <myron.stowe@redhat.com> wrote:
>> > From: Myron Stowe <mstowe@redhat.com>
>> >
>> > Make sure the removal of mappings uses the same logic that put the
>> > mappings in place.
>> >
>> > Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
>> > ---
>> >
>> >  drivers/acpi/osl.c |    2 +-
>> >  1 files changed, 1 insertions(+), 1 deletions(-)
>> >
>> > diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
>> > index 412a1e0..5aef087 100644
>> > --- a/drivers/acpi/osl.c
>> > +++ b/drivers/acpi/osl.c
>> > @@ -347,7 +347,7 @@ 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))
>> > +       if (should_use_kmap(pfn))
>> >                kunmap(pfn_to_page(pfn));
>> >        else
>> >                iounmap(vaddr);
>> >
>>
>> Whatever happened to the question of why we have arch-specific
>> ioremap() behavior?  It's good to make map/unmap symmetric, but it'd
>> be better to get rid of the ioremap/kmap hack.
>
> +cc ingo
>
> We never received any explanation for why ioremap() failed for Ying with
> RAM on x86.  Last I saw Ying asked Ingo for some input here but there
> was never any reply -
> http://marc.info/?l=linux-acpi&m=132788392604738&w=2
>
> I like your idea of possibly changing ioremap's implementation so that
> it would handle requests related to RAM - by using kmap() internally
> when necessary - so that a *user* wouldn't need to care what
> architecture we're on.  I, however, feel like I don't have enough
> experience with the memory management subsystem to know if such a tactic
> would fly or not so was uncomfortable proceeding along those lines.  As
> a result, I just wanted to get this in for the meantime.

I dunno if you're comfortable with it, but you can always propose a
patch doing it how you think it should be done.  People are more apt
to respond to a concrete patch than to an abstract question about why
things are the way they are.

Bjorn