linux-kernel - Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,

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Date:   Sun, 29 Aug 2021 18:26:20 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Richard Henderson <rth@...ddle.net>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        James E J Bottomley <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        "David S . Miller" <davem@...emloft.net>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        X86 ML <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        linux-alpha@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}

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 changing
> anything drastic here, just give the low level subsystem a better hint about
> 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, 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:



diff --git a/include/linux/audited.h b/include/linux/audited.h
new file mode 100644
index 000000000000..e23fd6ad50db
--- /dev/null
+++ b/include/linux/audited.h
@@ -0,0 +1,3 @@
+#ifndef AUDITED_MODULE
+#define AUDITED_MODULE
+#endif

Now any audited driver must do
#include <linux/audited.h>
first of all.
Implementation-wise it can do any number of things,
e.g. if you like then sure you can do:

#ifdef AUDITED_MODULE
#define pci_ioremap pci_ioremap_shared
#else
#define pci_ioremap pci_ioremap
#endif

but you can also thinkably do something like (won't work,
but just to give you the idea):

#ifdef AUDITED_MODULE
#define __init __init
#else
#define __init
#endif

or any number of hacks like this.


-- 
MST