linux-kernel - Re: [patch 22/37] arm64: smp: Switch to hotplug core state synchronization

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Message-ID: <87ildjys7f.ffs@tglx>
Date:   Wed, 26 Apr 2023 10:15:48 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mark Rutland <mark.rutland@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        David Woodhouse <dwmw@...radead.org>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Brian Gerst <brgerst@...il.com>,
        Arjan van de Veen <arjan@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Paul McKenney <paulmck@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Sean Christopherson <seanjc@...gle.com>,
        Oleksandr Natalenko <oleksandr@...alenko.name>,
        Paul Menzel <pmenzel@...gen.mpg.de>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Piotr Gorski <lucjan.lucjanov@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        David Woodhouse <dwmw@...zon.co.uk>,
        Usama Arif <usama.arif@...edance.com>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>, Guo Ren <guoren@...nel.org>,
        linux-csky@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org, Sabin Rapan <sabrapan@...zon.com>
Subject: Re: [patch 22/37] arm64: smp: Switch to hotplug core state
 synchronization

On Wed, Apr 26 2023 at 08:59, Mark Rutland wrote:
> On Tue, Apr 25, 2023 at 09:51:12PM +0200, Thomas Gleixner wrote:
>> If not then it's just yet another way of DoS which is an "acceptable"
>> attack as it only affects availability but not confidentiality.
>
> Sure.
>
> My thinking is that this is an attack against the *integrity* of the guest
> (since the vCPU that gets unpasued may write to memory), and so it's
> potentially more than just a DoS.
>
> I only mention this because I'd like to account for that on arm64, and if other
> architectures also wanted to handle that it might make sense to have some
> common infrastructure to track whether CPUs are potentially still within the
> kernel.

Fair enough.