linux-kernel - Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user mappings

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Message-ID: <alpine.DEB.2.21.1910291011090.5411@www.lameter.com>
Date:   Tue, 29 Oct 2019 10:12:04 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Mike Rapoport <rppt@...nel.org>
cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        linux-kernel@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, linux-api@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH RFC] mm: add MAP_EXCLUSIVE to create exclusive user
 mappings



On Tue, 29 Oct 2019, Mike Rapoport wrote:

> I've talked with Thomas yesterday and he suggested something similar:
>
> When the MAP_EXCLUSIVE request comes for the first time, we allocate a huge
> page for it and then use this page as a pool of 4K pages for subsequent
> requests. Once this huge page is full we allocate a new one and append it
> to the pool. When all the 4K pages that comprise the huge page are freed
> the huge page is collapsed.

Or write a device driver that allows you to mmap a secure area and avoid
all core kernel modifications?

/dev/securemem or so?

It may exist already.