Re: [PATCH 4/8] spapr_pci: Fix memory leak of vmstate_spapr_pci

[David Gibson]

On Mon, Dec 28, 2020 at 08:10:31AM +0000, gaojinhao wrote:
> Hi David,
> Firstly, thank you for you review. And then for your review, I worry
> that a memory leak will occur if QEMU exits after saves vmsd. So, we
> free it in post_save func.

If qemu exits, all its memory will be freed, so we don't care.

> 
> Jinhao Gao
> 
> -----Original Message-----
> From: David Gibson [mailto:david@gibson.dropbear.id.au] 
> Sent: 2020-12-28 14:58
> To: gaojinhao <gaojinhao@huawei.com>
> Cc: qemu-devel@nongnu.org; qemu-ppc@nongnu.org; Marc-André Lureau 
> <marcandre.lureau@redhat.com>; Stefan Berger <stefanb@linux.vnet.ibm.com>; 
> Michael S . Tsirkin <mst@redhat.com>; Jason Wang <jasowang@redhat.com>; Greg 
> Kurz <groug@kaod.org>; Juan Quintela <quintela@redhat.com>; Dr . David Alan 
> Gilbert <dgilbert@redhat.com>; Wanghaibin (D) <wanghaibin.wang@huawei.com>; 
> zhukeqian <zhukeqian1@huawei.com>
> Subject: Re: [PATCH 4/8] spapr_pci: Fix memory leak of vmstate_spapr_pci
> 
> On Sat, Dec 26, 2020 at 06:33:43PM +0800, g00517791 wrote:
> > From: Jinhao Gao <gaojinhao@huawei.com>
> > 
> > When VM migrate VMState of spapr_pci, the field(msi_devs) of spapr_pci 
> > having a flag of VMS_ALLOC need to allocate memory. If the src doesn't 
> > free memory of msi_devs in SaveStateEntry of spapr_pci after QEMUFile 
> > save VMState of spapr_pci, it may result in memory leak of msi_devs. 
> > We add the post_save func to free memory, which prevents memory leak.
> > 
> > Signed-off-by: Jinhao Gao <gaojinhao@huawei.com>
> 
> Not really a memory leak, since it will get freed on the next pre_save.  But, 
> we might as well free it earlier if we can ,so
> 
> Acked-by: David Gibson <david@gibson.dropbear.id.au>
> 
> > ---
> >  hw/ppc/spapr_pci.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c index 
> > 76d7c91e9c..1b2b940606 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -2173,6 +2173,16 @@ static int spapr_pci_pre_save(void *opaque)
> >      return 0;
> >  }
> >  
> > +static int spapr_pci_post_save(void *opaque) {
> > +    SpaprPhbState *sphb = opaque;
> > +
> > +    g_free(sphb->msi_devs);
> > +    sphb->msi_devs = NULL;
> > +    sphb->msi_devs_num = 0;
> > +    return 0;
> > +}
> > +
> >  static int spapr_pci_post_load(void *opaque, int version_id)  {
> >      SpaprPhbState *sphb = opaque;
> > @@ -2205,6 +2215,7 @@ static const VMStateDescription vmstate_spapr_pci = {
> >      .version_id = 2,
> >      .minimum_version_id = 2,
> >      .pre_save = spapr_pci_pre_save,
> > +    .post_save = spapr_pci_post_save,
> >      .post_load = spapr_pci_post_load,
> >      .fields = (VMStateField[]) {
> >          VMSTATE_UINT64_EQUAL(buid, SpaprPhbState, NULL),
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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