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From: Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}
Date: Sun, 29 Aug 2021 22:11:46 -0700
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>, "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Peter Zijlstra <peterz@infradead.org>, Andy Lutomirski <luto@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>, Richard Henderson <rth@twiddle.net>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, James E J Bottomley <James.Bottomley@hansenpartnership.com>, Helge Deller <deller@gmx.de>, "David S . Miller" <davem@davemloft.net>, Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>, Peter H Anvin <hpa@zytor.com>, Dave Hansen <dave.hansen@intel.com>, Tony Luck <tony.luck@intel.com>, Kirill Shutemov <kirill.shutemov@lin>


On 8/29/2021 3:26 PM, Michael S. Tsirkin wrote:
> On Sun, Aug 29, 2021 at 09:17:53AM -0700, Andi Kleen wrote:
>> Also I changing this single call really that bad? It's not that we chang=
ing
>> anything drastic here, just give the low level subsystem a better hint a=
bout
>> the intention. If you don't like the function name, could make it an
>> argument instead?
> My point however is that the API should say that the
> driver has been audited,

We have that status in the struct device. If you want to tie the ioremap=20
to that we could define a ioremap_device() with a device argument and=20
decide based on that.

Or we can add _audited to the name. ioremap_shared_audited?

> not that the mapping has been
> done in some special way. For example the mapping can be
> in some kind of wrapper, not directly in the driver.
> However you want the driver validated, not the wrapper.
>
> Here's an idea:


I don't think magic differences of API behavior based on some define are=20
a good idea.=C2=A0 That's easy to miss.

That's a "COME FROM" in API design.

Also it wouldn't handle the case that a driver has both private and=20
shared ioremaps, e.g. for BIOS structures.

And we've been avoiding that drivers can self declare auditing, we've=20
been trying to have a separate centralized list so that it's easier to=20
enforce and avoids any cut'n'paste mistakes.

-Andi