From: Paolo Bonzini <pbonzini@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>, kvm@vger.kernel.org
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Joao Martins <joao.m.martins@oracle.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Metin Kaya <metikaya@amazon.co.uk>,
Paul Durrant <pdurrant@amazon.co.uk>
Subject: Re: [PATCH 1/2] KVM: x86/xen: PV oneshot timer fixes
Date: Wed, 9 Mar 2022 17:28:00 +0100 [thread overview]
Message-ID: <baa1d8da-fd9d-39f4-269e-4af50936e042@redhat.com> (raw)
In-Reply-To: <4f1b299dd989640b5c9e8f23a9b90de357581b62.camel@infradead.org>
On 3/9/22 17:11, David Woodhouse wrote:
> That's OK, as the pending events are in the shared_info and vcpu_info
> regions which we have explicitly declared exempt from dirty tracking.
> Userspace must always consider them dirty any time an interrupt (which
> includes timers) might be delivered, so it has to migrate that memory
> in the final sync, after serializing the vCPU state.
>
> In the local APIC delivery mode, the actual interrupt is injected as an
> MSI, so userspace needs to read the timer state before the local APIC
> state.
Please document this. It's not obvious from the fact that they're not
dirty-tracked.
Paolo
next prev parent reply other threads:[~2022-03-09 16:36 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 14:38 [PATCH 0/2] KVM: Xen PV timer fixups David Woodhouse
2022-03-09 14:38 ` [PATCH 1/2] KVM: x86/xen: PV oneshot timer fixes David Woodhouse
2022-03-09 15:39 ` Paolo Bonzini
2022-03-09 16:11 ` David Woodhouse
2022-03-09 16:28 ` Paolo Bonzini [this message]
2022-03-09 16:37 ` David Woodhouse
2022-03-09 16:39 ` Paolo Bonzini
2022-03-09 16:41 ` [PATCH v2 " David Woodhouse
2022-03-13 14:30 ` Paolo Bonzini
2022-03-13 14:57 ` David Woodhouse
2022-03-09 14:38 ` [PATCH 2/2] KVM: x86/xen: Update self test for Xen PV timers David Woodhouse
2022-03-09 14:47 ` [PATCH 0/2] KVM: Xen PV timer fixups David Woodhouse
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