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Re: [Qemu-devel] [PATCH v5 04/10] cpu: Reclaim vCPU objects


From: Bharata B Rao
Subject: Re: [Qemu-devel] [PATCH v5 04/10] cpu: Reclaim vCPU objects
Date: Wed, 2 Dec 2015 09:20:38 +0530
User-agent: Mutt/1.5.23 (2014-03-12)

On Mon, Nov 30, 2015 at 06:30:52PM +1100, Alexey Kardashevskiy wrote:
> On 11/20/2015 11:54 PM, Bharata B Rao wrote:
> >From: Gu Zheng <address@hidden>
> >
> >In order to deal well with the kvm vcpus (which can not be removed without 
> >any
> >protection), we do not close KVM vcpu fd, just record and mark it as stopped
> >into a list, so that we can reuse it for the appending cpu hot-add request if
> >possible. It is also the approach that kvm guys suggested:
> >https://www.mail-archive.com/address@hidden/msg102839.html
> >
> >Signed-off-by: Chen Fan <address@hidden>
> >Signed-off-by: Gu Zheng <address@hidden>
> >Signed-off-by: Zhu Guihua <address@hidden>
> >Signed-off-by: Bharata B Rao <address@hidden>
> >                [- Explicit CPU_REMOVE() from qemu_kvm/tcg_destroy_vcpu()
> >                   isn't needed as it is done from cpu_exec_exit()]
> >Reviewed-by: David Gibson <address@hidden>
> >---
> >  cpus.c               | 41 +++++++++++++++++++++++++++++++++++++
> >  include/qom/cpu.h    | 10 +++++++++
> >  include/sysemu/kvm.h |  1 +
> >  kvm-all.c            | 57 
> > +++++++++++++++++++++++++++++++++++++++++++++++++++-
> >  kvm-stub.c           |  5 +++++
> >  5 files changed, 113 insertions(+), 1 deletion(-)
> >
> >diff --git a/cpus.c b/cpus.c
> >index 877bd70..af2b274 100644
> >--- a/cpus.c
> >+++ b/cpus.c
> >@@ -953,6 +953,21 @@ void async_run_on_cpu(CPUState *cpu, void (*func)(void 
> >*data), void *data)
> >      qemu_cpu_kick(cpu);
> >  }
> >
> >+static void qemu_kvm_destroy_vcpu(CPUState *cpu)
> >+{
> >+    if (kvm_destroy_vcpu(cpu) < 0) {
> >+        error_report("kvm_destroy_vcpu failed.\n");
> >+        exit(EXIT_FAILURE);
> >+    }
> >+
> >+    object_unparent(OBJECT(cpu));
> >+}
> >+
> >+static void qemu_tcg_destroy_vcpu(CPUState *cpu)
> >+{
> >+    object_unparent(OBJECT(cpu));
> >+}
> >+
> >  static void flush_queued_work(CPUState *cpu)
> >  {
> >      struct qemu_work_item *wi;
> >@@ -1053,6 +1068,11 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
> >              }
> >          }
> >          qemu_kvm_wait_io_event(cpu);
> >+        if (cpu->exit && !cpu_can_run(cpu)) {
> >+            qemu_kvm_destroy_vcpu(cpu);
> >+            qemu_mutex_unlock(&qemu_global_mutex);
> 
> 
> Nit: qemu_mutex_unlock_iothread() may be? Or it is important for
> iothread_locked to remain "true"? It does not seem to be used much though.

This patch is quite old and qemu_global_mutex got changed to
qemu_mutex_unlock_iothread() some time ago in this part of the code.

Thanks for noticing this, will fix this in next version.

Regards,
Bharata.




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