linux-kernel - Re: ioremap() called early from pnv_pci_init_ioda

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Message-Id: <1589013519.0fzm2px5cz.astroid@bobo.none>
Date:   Sat, 09 May 2020 18:43:30 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Qian Cai <cai@....pw>, Oliver O'Halloran <oohall@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: ioremap() called early from pnv_pci_init_ioda_phb()

Excerpts from Oliver O'Halloran's message of May 9, 2020 6:11 pm:
> On Sat, May 9, 2020 at 12:41 AM Qian Cai <cai@....pw> wrote:
>>
>>  Booting POWER9 PowerNV has this message,
>>
>> "ioremap() called early from pnv_pci_init_ioda_phb+0x420/0xdfc. Use early_ioremap() instead”
>>
>> but use the patch below will result in leaks because it will never call early_iounmap() anywhere. However, it looks me it was by design that phb->regs mapping would be there forever where it would be used in pnv_ioda_get_inval_reg(), so is just that check_early_ioremap_leak() initcall too strong?
> 
> The warning there is junk. The PHBs are setup at boot and never torn
> down so we're not "leaking" the mapping. It's supposed to be there for
> the lifetime of the kernel.
> 
> That said, we could probably move the PCI setup to a point later in
> boot where the normal ioremap can be be used. We would have to check
> for initcalls which depend on the PHBs being setup and delay those too
> though.

I think it helps to unify code a bit more and take special cases out of 
ioremap to have all these early calls use early_ioremap.

We actually do want to move these later if possible too, on radix they 
use memblock for page tables, and on hash they don't even set up proper 
kernel page tables but just bolt PTEs into the hash table.

Thanks,
Nick