linux-kernel - Re: [RFC PATCH v3 1/2] KVM: arm64: Move CMOs from user_mem

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Message-ID: <20210407205701.GA16198@willie-the-truck>
Date:   Wed, 7 Apr 2021 21:57:02 +0100
From:   Will Deacon <will@...nel.org>
To:     Alexandru Elisei <alexandru.elisei@....com>
Cc:     Yanan Wang <wangyanan55@...wei.com>, Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Gavin Shan <gshan@...hat.com>,
        Quentin Perret <qperret@...gle.com>,
        wanghaibin.wang@...wei.com, zhukeqian1@...wei.com,
        yuzenghui@...wei.com
Subject: Re: [RFC PATCH v3 1/2] KVM: arm64: Move CMOs from user_mem_abort to
 the fault handlers

On Wed, Apr 07, 2021 at 04:31:31PM +0100, Alexandru Elisei wrote:
> On 3/26/21 3:16 AM, Yanan Wang wrote:
> > We currently uniformly permorm CMOs of D-cache and I-cache in function
> > user_mem_abort before calling the fault handlers. If we get concurrent
> > guest faults(e.g. translation faults, permission faults) or some really
> > unnecessary guest faults caused by BBM, CMOs for the first vcpu are
> 
> I can't figure out what BBM means.

Oh, I know that one! BBM means "Break Before Make". Not to be confused with
DBM (Dirty Bit Management) or BFM (Bit Field Move).

Will