linux-kernel - Re: [PATCH v38 10/24] mm: Add vm

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Message-Id: <2321E653-F629-44D7-91C3-F42F42AF4EF6@amacapital.net>
Date:   Fri, 25 Sep 2020 21:15:19 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Haitao Huang <haitao.huang@...ux.intel.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        linux-sgx@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jethro Beekman <jethro@...tanix.com>,
        Darren Kenny <darren.kenny@...cle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        asapek@...gle.com, Borislav Petkov <bp@...en8.de>,
        "Xing, Cedric" <cedric.xing@...el.com>, chenalexchen@...gle.com,
        Conrad Parker <conradparker@...gle.com>, cyhanish@...gle.com,
        "Huang, Haitao" <haitao.huang@...el.com>,
        Josh Triplett <josh@...htriplett.org>,
        "Huang, Kai" <kai.huang@...el.com>,
        "Svahn, Kai" <kai.svahn@...el.com>, Keith Moyer <kmoy@...gle.com>,
        Christian Ludloff <ludloff@...gle.com>,
        Neil Horman <nhorman@...hat.com>,
        Nathaniel McCallum <npmccallum@...hat.com>,
        Patrick Uiterwijk <puiterwijk@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>, yaozhangx@...gle.com
Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect()


> On Sep 25, 2020, at 12:53 PM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
> On 9/25/20 12:43 PM, Sean Christopherson wrote:
>>> That means that the intent argument (SGX_PROT_*) is currently unused.
>> No, the intent argument is used (eventually) by SGX's ->mprotect()
>> implementation, i.e. sgx_mprotect() enforces that the actual protections are a
>> subset of the declared/intended protections.
>> 
>> If ->mprotect() is not merged, then it yes, it will be unused.
> 
> OK, I think I've got it.
> 
> I think I'm OK with adding ->mprotect().  As long as folks buy into the
> argument that intent needs to be checked at mmap() time, they obviously
> need to be checked at mprotect() too.
> 
> Jarkko, if you want to try and rewrite the changelog, capturing the
> discussion here and reply, I think I can ack the resulting patch.  I
> don't know if that will satisfy the request from Boris from an ack from
> a "mm person", but we can at least start there. :)

I think I agree. ->mprotect seems reasonable to me.

FWIW, I don’t think I should ack this particular thing — it was, to a decent extent, my suggestion in the first place, so I’m biased. I think it turned into something reasonable, and the ->mprotect mechanism seems easily supportable and plausibly useful for other purposes down the road.

> 
> Please be judicious in what you include in the changelog.  There's been
> a lot of detritus in them.  Let's keep it as short, sweet, simple and on
> topic as we can.