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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     Mark Rutland <mark.rutland@arm.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        David Woodhouse <dwmw@infradead.org>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
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        "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
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        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        linux-riscv@lists.infradead.org, Sabin Rapan <sabrapan@amazon.com>
Subject: Re: [patch 22/37] arm64: smp: Switch to hotplug core state
 synchronization
In-Reply-To: <ZEjZ3pHjQWn4drs8@FVFF77S0Q05N>
References: <20230414225551.858160935@linutronix.de>
 <20230414232310.569498144@linutronix.de> <ZD1q3TF2ixVD1f2M@FVFF77S0Q05N>
 <87ttx3zqof.ffs@tglx> <ZEjZ3pHjQWn4drs8@FVFF77S0Q05N>
Date:   Wed, 26 Apr 2023 10:15:48 +0200
Message-ID: <87ildjys7f.ffs@tglx>
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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.