ARM: xip: disable PATCH_PHYS_VIRT for ARCH_MULTIPLATFORM when XIP

Commit Message

Geert Uytterhoeven Feb. 8, 2017, 6:46 p.m. UTC

Hi Russell,

On Wed, Feb 8, 2017 at 7:39 PM, Russell King - ARM Linux
<[e-mail]> wrote:
> On Wed, Feb 08, 2017 at 06:53:14PM +0100, Geert Uytterhoeven wrote:
>> The problem is that "multiplatform" may mean one of two things:
>>   1. Build a single kernel that can run on multiple platforms.
>>      This is tricky when enabling XIP and/or NOMMU, as the physical parameters
>>      must be compatible with all platforms. But building a kernel with the
>>      right parameters is the responsibility of the user.
>>      I.e. don't shoot yourself in the foot.
>>   2. Your platform uses the arch/arm multiplatform framework.
>>
>> As everything is being migrated to 2, not allowing XIP and/or NOMMU on
>> "multiplatform" is IMHO an insane limitation.
>
> There _isn't_ a framework.  What there is are a collection of Kconfig
> options that multiplatform provides you that can also be selected by
> any other configuration route.
>
> (2) really doesn't apply.
>
> The real issue is that board stuff ends up with a "depends on MULTI_xxx"
> which needs to be bypassed.  That's pretty easy to do - I've done it as
> a proof of concept a few years ago when this exact same thing came up
> for !MMU, and since then I've been NAKing and refusing to apply patches
> that try to re-use multiplat for !MMU.

So you mean this:


?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [e-mail]

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Comments

Russell King (Oracle) Feb. 8, 2017, 6:55 p.m. UTC | #1

On Wed, Feb 08, 2017 at 07:46:55PM +0100, Geert Uytterhoeven wrote:
> Hi Russell,
> 
> On Wed, Feb 8, 2017 at 7:39 PM, Russell King - ARM Linux
> <[e-mail]> wrote:
> > On Wed, Feb 08, 2017 at 06:53:14PM +0100, Geert Uytterhoeven wrote:
> >> The problem is that "multiplatform" may mean one of two things:
> >>   1. Build a single kernel that can run on multiple platforms.
> >>      This is tricky when enabling XIP and/or NOMMU, as the physical parameters
> >>      must be compatible with all platforms. But building a kernel with the
> >>      right parameters is the responsibility of the user.
> >>      I.e. don't shoot yourself in the foot.
> >>   2. Your platform uses the arch/arm multiplatform framework.
> >>
> >> As everything is being migrated to 2, not allowing XIP and/or NOMMU on
> >> "multiplatform" is IMHO an insane limitation.
> >
> > There _isn't_ a framework.  What there is are a collection of Kconfig
> > options that multiplatform provides you that can also be selected by
> > any other configuration route.
> >
> > (2) really doesn't apply.
> >
> > The real issue is that board stuff ends up with a "depends on MULTI_xxx"
> > which needs to be bypassed.  That's pretty easy to do - I've done it as
> > a proof of concept a few years ago when this exact same thing came up
> > for !MMU, and since then I've been NAKing and refusing to apply patches
> > that try to re-use multiplat for !MMU.
> 
> So you mean this:
> 
> --- a/arch/arm/mach-shmobile/Kconfig
> +++ b/arch/arm/mach-shmobile/Kconfig
> @@ -31,7 +31,7 @@ config ARCH_RMOBILE
> 
>  menuconfig ARCH_RENESAS
>         bool "Renesas ARM SoCs"
> -       depends on ARCH_MULTI_V7 && MMU
> +       depends on MMU
>         select ARCH_DMA_ADDR_T_64BIT if ARM_LPAE
>         select ARCH_SHMOBILE
>         select ARCH_SHMOBILE_MULTI

I don't see the connection, sorry.  That looks totally broken to me,
because you now end up being able to select it when you have (eg)
something like ARCH_RPC enabled, and that's totally insane.

If you think the above patch in some way represents what I was saying,
that's wrong as well.

Patch

--- a/arch/arm/mach-shmobile/Kconfig
+++ b/arch/arm/mach-shmobile/Kconfig
@@ -31,7 +31,7 @@  config ARCH_RMOBILE

 menuconfig ARCH_RENESAS
        bool "Renesas ARM SoCs"
-       depends on ARCH_MULTI_V7 && MMU
+       depends on MMU
        select ARCH_DMA_ADDR_T_64BIT if ARM_LPAE
        select ARCH_SHMOBILE
        select ARCH_SHMOBILE_MULTI