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Subject: Re: [PATCHv3 33/33] mm, x86: introduce PR_SET_MAX_VADDR and PR_GET_MAX_VADDR
To: Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>
CC: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Arnd Bergmann <arnd@arndb.de>, Andi Kleen <ak@linux.intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
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        linux-mm <linux-mm@kvack.org>,
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On February 17, 2017 3:02:33 PM PST, Andy Lutomirski <luto@amacapital.net> wrote:
>On Fri, Feb 17, 2017 at 1:01 PM, Linus Torvalds
><torvalds@linux-foundation.org> wrote:
>> On Fri, Feb 17, 2017 at 12:12 PM, Andy Lutomirski
><luto@amacapital.net> wrote:
>>>
>>> At the very least, I'd want to see
>>> MAP_FIXED_BUT_DONT_BLOODY_UNMAP_ANYTHING.  I *hate* the current
>>> interface.
>>
>> That's unrelated, but I guess w could add a MAP_NOUNMAP flag, and
>then
>> you can use MAP_FIXED | MAP_NOUNMAP or something.
>>
>> But that has nothing to do with the 47-vs-56 bit issue.
>>
>>> How about MAP_LIMIT where the address passed in is interpreted as an
>>> upper bound instead of a fixed address?
>>
>> Again, that's a unrelated semantic issue. Right now - if you don't
>> pass in MAP_FIXED at all, the "addr" argument is used as a starting
>> value for deciding where to find an unmapped area. But there is no
>way
>> to specify the end. That would basically be what the process control
>> thing would be (not per-system-call, but per-thread ).
>>
>
>What I'm trying to say is: if we're going to do the route of 48-bit
>limit unless a specific mmap call requests otherwise, can we at least
>have an interface that doesn't suck?

Let's not, please.

But we really want this interface anyway.
-- 
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