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

[gaojinhao <gaojinhao@huawei.com>]

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.

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),

-- 
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