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From: Paolo Bonzini <pbonzini@redhat.com>
To: Oliver Upton <oupton@google.com>
Cc: kvm list <kvm@vger.kernel.org>, Jim Mattson <jmattson@google.com>,
	Peter Shier <pshier@google.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [PATCH v3 0/5] Handle monitor trap flag during instruction emulation
Date: Thu, 27 Feb 2020 07:37:54 +0100	[thread overview]
Message-ID: <74650413-5cbc-6dd7-498e-22e89f1f6732@redhat.com> (raw)
In-Reply-To: <CAOQ_Qsg6DnSGU26xBJAQ6CGb6Lh5jX7VTvoXFZRnx3_f0eKYGQ@mail.gmail.com>

On 27/02/20 01:22, Oliver Upton wrote:
> Are there any strong opinions about how the newly introduced nested
> state should be handled across live migrations? When applying this
> patch set internally I realized live migration would be busted in the
> case of a kernel rollback (i.e. a kernel with this patchset emits the
> nested state, kernel w/o receives it + refuses).

Only if you use MTF + emulation.  In this case it's a pure bugfix so
it's okay to break backwards migration.  If it's really a new feature,
it should support KVM_ENABLE_CAP to enable it.

Paolo

> Easy fix is to only turn on the feature once it is rollback-proof, but
> I wonder if there is any room for improvement on this topic..


  reply	other threads:[~2020-02-27  6:38 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-07 10:36 [PATCH v3 0/5] Handle monitor trap flag during instruction emulation Oliver Upton
2020-02-07 10:36 ` [PATCH v3 1/5] KVM: x86: Mask off reserved bit from #DB exception payload Oliver Upton
2020-02-07 10:36 ` [PATCH v3 2/5] KVM: nVMX: Handle pending #DB when injecting INIT VM-exit Oliver Upton
2020-02-07 10:36 ` [PATCH v3 3/5] KVM: x86: Deliver exception payload on KVM_GET_VCPU_EVENTS Oliver Upton
2020-02-07 10:36 ` [PATCH v3 4/5] KVM: nVMX: Emulate MTF when performing instruction emulation Oliver Upton
2020-02-07 10:36 ` [kvm-unit-tests PATCH v3 5/5] x86: VMX: Add tests for monitor trap flag Oliver Upton
2020-02-25  0:09   ` Oliver Upton
2020-02-25  7:36     ` Paolo Bonzini
2020-02-25  7:52       ` Oliver Upton
2020-02-26  0:13     ` Krish Sadhukhan
2020-02-26  0:55       ` Oliver Upton
2020-02-12 11:34 ` [PATCH v3 0/5] Handle monitor trap flag during instruction emulation Paolo Bonzini
2020-02-27  0:22   ` Oliver Upton
2020-02-27  6:37     ` Paolo Bonzini [this message]
2020-02-27  9:11       ` Oliver Upton

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