linux-kernel - Re: [PATCH v3 5/9] x86/mm/tlb: Privatize cpu

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: <92B64D24-04DD-45A6-86A4-758CD73E0909@vmware.com>
Date:   Fri, 19 Jul 2019 18:54:00 +0000
From:   Nadav Amit <namit@...are.com>
To:     Dave Hansen <dave.hansen@...el.com>
CC:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v3 5/9] x86/mm/tlb: Privatize cpu_tlbstate

> On Jul 19, 2019, at 11:48 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
> On 7/19/19 11:43 AM, Nadav Amit wrote:
>> Andy said that for the lazy tlb optimizations there might soon be more
>> shared state. If you prefer, I can move is_lazy outside of tlb_state, and
>> not set it in any alternative struct.
> 
> I just wanted to make sure that we capture these rules:
> 
> 1. If the data is only ever accessed on the "owning" CPU via
>   this_cpu_*(), put it in 'tlb_state'.
> 2. If the data is read by other CPUs, put it in 'tlb_state_shared'.
> 
> I actually like the idea of having two structs.

Yes, that’s exactly the idea. In the (1) case, we may even be able to mark
the struct with __thread qualifier, which IIRC would prevent memory barriers
from causing these values being reread.