linux-kernel - Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code

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: <20201118112952.GB7472@zn.tnic>
Date:   Wed, 18 Nov 2020 12:29:52 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, dave.hansen@...ux.intel.com, luto@...nel.org,
        peterz@...radead.org, linux-kernel@...r.kernel.org,
        thomas.lendacky@....com, jroedel@...e.de, konrad.wilk@...cle.com,
        jan.setjeeilers@...cle.com, junaids@...gle.com, oweisse@...gle.com,
        rppt@...ux.vnet.ibm.com, graf@...zon.de, mgross@...ux.intel.com,
        kuzuno@...il.com, Mel Gorman <mgorman@...hsingularity.net>
Subject: Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code

On Wed, Nov 18, 2020 at 08:41:42AM +0100, Alexandre Chartre wrote:
> Well, it looks like I wrongfully assume that KPTI was a well known performance
> overhead since it was introduced (because it adds extra page-table switches),
> but you are right I should be presenting my own numbers.

Here's one recipe, courtesy of Mel:

https://github.com/gormanm/mmtests

"
./run-mmtests.sh --no-monitor --config configs/config-workload-poundsyscall test-default

# reboot the machine with pti disabled

./run-mmtests.sh --no-monitor --config configs/config-workload-poundsyscall test-nopti

poundsyscall just calls getppid() so it's a light-weight syscall and a
proxy measure for syscall entry/exit costs. To do the actual compare

cd work/log
../../compare-kernels.sh

and see what gain there is from disabling pti. If you want to compare
the other direction

../../compare-kernels.sh --baseline test-nopti --compare test-default

If you get an error about BinarySearch

(echo y;echo o conf prerequisites_policy follow;echo o conf commit)|cpan
yes | cpan List::BinarySearch

Only se the second line if you want to interactively confirm what cpan
should download and install."

I've CCed him should you have any questions.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette