From: Sean Christopherson <seanjc@google.com>
To: Shivam Kumar <shivam.kumar1@nutanix.com>
Cc: pbonzini@redhat.com, kvm@vger.kernel.org,
Anurag Madnawat <anurag.madnawat@nutanix.com>,
Shaju Abraham <shaju.abraham@nutanix.com>,
Manish Mishra <manish.mishra@nutanix.com>
Subject: Re: [PATCH 3/6] Add KVM_CAP_DIRTY_QUOTA_MIGRATION and handle vCPU page faults.
Date: Wed, 1 Dec 2021 17:22:46 +0000 [thread overview]
Message-ID: <YaevZjcW7bMsrBPg@google.com> (raw)
In-Reply-To: <d9129cda-ebd9-aec3-3f04-bb989c509ac1@nutanix.com>
On Thu, Nov 25, 2021, Shivam Kumar wrote:
>
> On 20/11/21 1:51 am, Shivam Kumar wrote:
> >
> > On 20/11/21 1:36 am, Sean Christopherson wrote:
> > > Actually, if we go the route of using kvm_run to report and update the
> > > count/quota, we don't even need a capability. Userspace can signal each
> > > vCPU to induce an exit to userspace, e.g. at the start of migration, then
> > > set the desired quota/count in vcpu->kvm_run and stuff exit_reason so
> > > that KVM updates the quota/count on the subsequent KVM_RUN. No locking
> > > or requests needed, and userspace can reset the count at will, it just
> > > requires a signal.
> > >
> > > It's a little weird to overload exit_reason like that, but if that's a
> > > sticking point we could add a flag in kvm_run somewhere. Requiring an
> > > exit to userspace at the start of migration doesn't seem too onerous.
> >
> > Yes, this path looks flaw-free. We will explore the complexity and how
> > we can simplify its implementation.
>
> Is it okay to define the per-vcpu dirty quota and dirty count in the kvm_run
> structure itself? It can save space and reduce the complexity of the
> implemenation by large margin.
Paolo, I'm guessing this question is directed at you since I made the suggestion :-)
next prev parent reply other threads:[~2021-12-01 17:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-14 14:57 [PATCH 0/6] KVM: Dirty Quota-Based VM Live Migration Auto-Converge Shivam Kumar
2021-11-14 14:57 ` [PATCH 1/6] Define data structures for dirty quota migration Shivam Kumar
2021-11-14 14:57 ` [PATCH 2/6] Init dirty quota flag and allocate memory for vCPUdqctx Shivam Kumar
2021-11-14 14:57 ` [PATCH 3/6] Add KVM_CAP_DIRTY_QUOTA_MIGRATION and handle vCPU page faults Shivam Kumar
2021-11-18 17:57 ` Sean Christopherson
2021-11-19 20:03 ` Shivam Kumar
[not found] ` <02b8fa86-a86b-969e-2137-1953639cb6d2@nutanix.com>
[not found] ` <YZgD0D4536s2DMem@google.com>
2021-11-19 20:21 ` Shivam Kumar
2021-11-25 8:43 ` Shivam Kumar
2021-12-01 17:22 ` Sean Christopherson [this message]
2021-11-14 14:57 ` [PATCH 4/6] Increment dirty counter for vmexit due to page write fault Shivam Kumar
2021-11-18 17:48 ` Sean Christopherson
2021-11-19 19:54 ` Shivam Kumar
2021-11-14 14:57 ` [PATCH 5/6] Exit to userspace when dirty quota is full Shivam Kumar
2021-11-14 14:57 ` [PATCH 6/6] Free vCPUdqctx memory on vCPU destroy Shivam Kumar
2021-11-18 17:46 ` [PATCH 0/6] KVM: Dirty Quota-Based VM Live Migration Auto-Converge Sean Christopherson
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