linux-kernel - RE: [PATCH v7 1/6] riscv: mm: dma-noncoherent: Switch using function pointers for cache management

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 for Android: free password hash cracker in your pocket

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

Message-ID: <OS0PR01MB592238D5F77EC74D1EBFB78E86909@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date:   Wed, 5 Apr 2023 06:08:27 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Prabhakar <prabhakar.csengg@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Samuel Holland <samuel@...lland.org>,
        Heiko Stuebner <heiko@...ech.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Rob Herring <robh+dt@...nel.org>, Guo Ren <guoren@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Andrew Jones <ajones@...tanamicro.com>
Subject: RE: [PATCH v7 1/6] riscv: mm: dma-noncoherent: Switch using function
 pointers for cache management

Hi Christoph Hellwig,

Thanks for the feedback.

> Subject: Re: [PATCH v7 1/6] riscv: mm: dma-noncoherent: Switch using
> function pointers for cache management
> 
> On Tue, Apr 04, 2023 at 06:24:16AM +0000, Biju Das wrote:
> > Just a question, how does function pointer makes a performance
> > difference compared to
> > ALTERNATIVE_X() macros?
> >
> > On both cases, we are pushing function parameters to stack, jumping to
> > the actual routine And then on return pop the variables from stack. Am I
> missing something here?
> 
> Indirect calls have always been more expensive, and with the hard- and
> software mitigations for spectre-like attacks they are becoming even more
> expensive.

Thanks for the info. I agree, it will be more expensive with software mitigations
for spectre-like attacks.

Cheers,
Biju