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

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Date:   Mon, 30 Aug 2021 17:23:17 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     "Michael S. Tsirkin" <mst@...hat.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 8/30/2021 1:59 PM, Michael S. Tsirkin wrote:
>
>> Or we can add _audited to the name. ioremap_shared_audited?
> But it's not the mapping that has to be done in handled special way.
> It's any data we get from device, not all of it coming from IO, e.g.
> there's DMA and interrupts that all have to be validated.
> Wouldn't you say that what is really wanted is just not running
> unaudited drivers in the first place?


Yes.


>
>> And we've been avoiding that drivers can self declare auditing, we've been
>> trying to have a separate centralized list so that it's easier to enforce
>> and avoids any cut'n'paste mistakes.
>>
>> -Andi
> Now I'm confused. What is proposed here seems to be basically that,
> drivers need to declare auditing by replacing ioremap with
> ioremap_shared.

Auditing is declared on the device model level using a central allow list.

But this cannot do anything to initcalls that run before probe, that's 
why an extra level of defense of ioremap opt-in is useful. But it's not 
the primary mechanism to declare a driver audited, that's the allow 
list. The ioremap is just another mechanism to avoid having to touch a 
lot of legacy drivers.

If we agree on that then the original proposed semantics of 
"ioremap_shared" may be acceptable?

-Andi