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Date:   Mon, 4 Mar 2019 16:55:05 -0500
From:   Konrad Rzeszutek Wilk <>
To:     Fenghua Yu <>
Cc:     Thomas Gleixner <>,
        Ingo Molnar <>, Borislav Petkov <>,
        H Peter Anvin <>,
        Paolo Bonzini <>,
        Dave Hansen <>,
        Ashok Raj <>,
        Peter Zijlstra <>,
        Ravi V Shankar <>,
        Xiaoyao Li <>,
        linux-kernel <>,
        x86 <>,
Subject: Re: [PATCH v4 00/17] x86/split_lock: Enable #AC exception for split
 locked accesses

> This capability may also find usage in cloud. A user process with split
> lock running in one guest can block other cores from accessing shared
> memory during its split locked memory access. That may cause overall
> system performance degradation.

"shared memory" ? As in memory shared between two guests?

> Split lock may open a security hole where malicious user code may slow
> down overall system by executing instructions with split lock.

How much slowdown are we talking?

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