linux-kernel - Re: [PATCH] KVM:Hyper-V reduce one kvm_write

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Message-ID: <2ee6e3c6-f1c1-a5e4-a2ca-934f3414f3a9@redhat.com>
Date:   Wed, 20 Dec 2017 10:45:02 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Rhett Rhett <rhett.kernel@...il.com>
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM:Hyper-V reduce one kvm_write_guest operation

On 20/12/2017 10:33, Rhett Rhett wrote:
> tsc_sequence  had been set to 0 before,  so the tsc page won't function.
> guest has no chance to read tsc page before the last write.
> 

kvm_write_guest is not atomic.  The guest can see a non-zero sequence
before the other fields have been set.

Paolo