linux-kernel - Re: [RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <6b0de827-738d-b3c5-fc79-8ca9047bad35@intel.com>
Date:   Wed, 24 Mar 2021 13:25:18 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Thomas Hellström (Intel) 
        <thomas_os@...pmail.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages

On 3/24/21 1:22 PM, Thomas Hellström (Intel) wrote:
>> We also have not been careful at *all* about how _PAGE_BIT_SOFTW* are
>> used.  It's quite possible we can encode another use even in the
>> existing bits.
>>
>> Personally, I'd just try:
>>
>> #define _PAGE_BIT_SOFTW5        57      /* available for programmer */
>>
> OK, I'll follow your advise here. FWIW I grepped for SW1 and it seems
> used in a selftest, but only for PTEs AFAICT.
> 
> Oh, and we don't care about 32-bit much anymore?

On x86, we have 64-bit PTEs when running 32-bit kernels if PAE is
enabled.  IOW, we can handle the majority of 32-bit CPUs out there.

But, yeah, we don't care about 32-bit. :)