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From:   Andy Lutomirski <luto@amacapital.net>
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Subject: Re: [PATCH v38 10/24] mm: Add vm_ops->mprotect()
Date:   Mon, 28 Sep 2020 18:37:54 -0700
Message-Id: <E16AF0FA-3017-4323-BDD9-56DCA33CED74@amacapital.net>
References: <20200928201959.GA3856@linux.intel.com>
Cc:     Dave Hansen <dave.hansen@intel.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Haitao Huang <haitao.huang@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
        linux-sgx@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jethro Beekman <jethro@fortanix.com>,
        Darren Kenny <darren.kenny@oracle.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        asapek@google.com, Borislav Petkov <bp@alien8.de>,
        "Xing, Cedric" <cedric.xing@intel.com>, chenalexchen@google.com,
        Conrad Parker <conradparker@google.com>, cyhanish@google.com,
        "Huang, Haitao" <haitao.huang@intel.com>,
        Josh Triplett <josh@joshtriplett.org>,
        "Huang, Kai" <kai.huang@intel.com>,
        "Svahn, Kai" <kai.svahn@intel.com>, Keith Moyer <kmoy@google.com>,
        Christian Ludloff <ludloff@google.com>,
        Neil Horman <nhorman@redhat.com>,
        Nathaniel McCallum <npmccallum@redhat.com>,
        Patrick Uiterwijk <puiterwijk@redhat.com>,
        David Rientjes <rientjes@google.com>,
        Thomas Gleixner <tglx@linutronix.de>, yaozhangx@google.com
In-Reply-To: <20200928201959.GA3856@linux.intel.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Precedence: bulk


> On Sep 28, 2020, at 1:20 PM, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.=
com> wrote:
>=20
> =EF=BB=BFOn Mon, Sep 28, 2020 at 12:45:27PM -0700, Dave Hansen wrote:
>>> On 9/28/20 12:32 PM, Jarkko Sakkinen wrote:
>>> My problem is that I fully agree what you say in your description but
>>> disagree on that EMODPE should not be mentioned.
>>=20
>> I'll just be very clear: I'm not willing to ack any patch with a
>> changelog that has more than a passing mention of EMODPE.
>>=20
>> Do what you think is best, but if sticking to your guns may deplete the
>> pool of folks willing to ack your patch.
>=20
> I do see it mentioned in other responses too in this thread, and not
> just mine.
>=20
> And here is even a request to get it to the changelog:
>=20
> https://lore.kernel.org/linux-sgx/1B23E216-0229-4BDD-8B09-807256A54AF5@ama=
capital.net/
>=20
> I'm absolutely fine not to mention EMODPE but after re-reading the
> thread, it is not like there is one voice on it. I don't really
> care all that much whether it is mentioned or not but there should
> be some reasonable logic behind the decision.

I don=E2=80=99t personally care that much about EMODPE but, you could probab=
ly get the point across with something like:

SGX=E2=80=99s EPCM permission bits do not obviate the need to enforce these r=
ules in the PTEs because enclaves can freely modify the EPCM permissions usi=
ng EMODPE.

IOW, EMODPE is not really special here; rather, EMODPE=E2=80=99s existence d=
emonstrates that EADD / EEXTEND are not special.