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Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB

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On Tue, 8 Sep 2015, Russell King - ARM Linux wrote:

> On Mon, Sep 07, 2015 at 03:40:36PM -0400, Nicolas Pitre wrote:
> > On Mon, 7 Sep 2015, Arnd Bergmann wrote:
> > 
> > > On Thursday 03 September 2015 21:24:00 Nicolas Pitre wrote:
> > > > If 768MB targets were common place then it could be worth changing the 
> > > > default vmalloc size to accommodate this memory size and testing all the 
> > > > other targets to make sure no regressions are introduced.  But given it 
> > > > is easy to change the default via the kernel cmdline, and that you lose 
> > > > only 8 MB otherwise, I don't think it is worth the trouble and/or the 
> > > > risk.
> > > 
> > > Agreed.
> > 
> > Well... I think there is a better solution.
> 
> Doesn't this clash with things like:
> 
> #define UNCACHEABLE_ADDR        0xff000000      /* IRQ_STAT */
> 
> ?

It looks like the move might actually "fix" it.  That UNCACHEABLE_ADDR 
is mapped with:

static struct map_desc ebsa110_io_desc[] __initdata = {
        /*
         * sparse external-decode ISAIO space
         */
        {       /* IRQ_STAT/IRQ_MCLR */
                .virtual        = (unsigned long)IRQ_STAT,
                .pfn            = __phys_to_pfn(TRICK4_PHYS),
                .length         = TRICK4_SIZE,
                .type           = MT_DEVICE
        },
[...]
};

This is passed to iotable_init(), then to create_mapping(). There you 
have:

        if ((md->type == MT_DEVICE || md->type == MT_ROM) &&
            md->virtual >= PAGE_OFFSET &&
            (md->virtual < VMALLOC_START || md->virtual >= VMALLOC_END)) {
                pr_warn("BUG: mapping for 0x%08llx at 0x%08lx out of vmalloc space\n",
                        (long long)__pfn_to_phys((u64)md->pfn), md->virtual);
        }

So you must have hit the above warning somehow. Incidentally, this 
IRQ_STAT entry is the only one that happened to be outside the vmalloc 
area. By moving VMALLOC_END from 0xff000000 to 0xff800000 the warning 
will be gone.


Nicolas
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[PATCH] ARM: fix bug which VMALLOC_START is lowwer than 0xf0000000 Yongtaek Lee <ytk.lee@samsung.com> - 2015-09-03 04:30 +0200
  [PATCH] ARM: fix bug which lowmem size is limited to 760MB Yongtaek Lee <ytk.lee@samsung.com> - 2015-09-03 07:20 +0200
  Re: [PATCH] ARM: fix bug which VMALLOC_START is lowwer than  0xf0000000 Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-03 10:10 +0200
    Re: Re: [PATCH] ARM: fix bug which VMALLOC_START is lowwer than  0xf0000000 Yongtaek Lee <ytk.lee@samsung.com> - 2015-09-03 10:30 +0200
      Re: Re: [PATCH] ARM: fix bug which VMALLOC_START is lowwer than  0xf0000000 Lucas Stach <l.stach@pengutronix.de> - 2015-09-03 10:40 +0200
        Re: Re: Re: [PATCH] ARM: fix bug which VMALLOC_START is lowwer than  0xf0000000 Yongtaek Lee <ytk.lee@samsung.com> - 2015-09-03 10:50 +0200
          Re: Re: Re: [PATCH] ARM: fix bug which VMALLOC_START is lowwer than  0xf0000000 Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-03 11:20 +0200
            [PATCH] ARM: fix bug which lowmem size is limited to 760MB Yongtaek Lee <ytk.lee@samsung.com> - 2015-09-03 12:40 +0200
              Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Nicolas Pitre <nicolas.pitre@linaro.org> - 2015-09-04 03:30 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Arnd Bergmann <arnd@arndb.de> - 2015-09-07 13:50 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Nicolas Pitre <nicolas.pitre@linaro.org> - 2015-09-07 17:40 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Nicolas Pitre <nicolas.pitre@linaro.org> - 2015-09-07 17:50 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Arnd Bergmann <arnd@arndb.de> - 2015-09-07 17:50 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Nicolas Pitre <nicolas.pitre@linaro.org> - 2015-09-07 21:50 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-08 02:20 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Nicolas Pitre <nicolas.pitre@linaro.org> - 2015-09-08 04:10 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-08 10:10 +0200
                Re: [PATCH] ARM: fix bug which lowmem size is limited to 760MB Nicolas Pitre <nicolas.pitre@linaro.org> - 2015-09-08 17:00 +0200
        Re: Re: [PATCH] ARM: fix bug which VMALLOC_START is lowwer than  0xf0000000 Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-03 11:10 +0200

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