> Subject: [EXTERNAL] Re: [PATCH 4/4] net/netvsc: cache device parameters for
> hot plug events
>
> On Mon, 27 Jan 2025 17:35:06 -0800
> lon...@linuxonhyperv.com wrote:
>
> > @@ -1409,9 +1424,6 @@ eth_hn_dev_uninit(struct rte_eth_dev *eth_dev)
> > ret_stop = hn_dev_stop(eth_dev);
> > hn_dev_close(eth_dev);
> >
> > - free(hv->vf_devargs);
> > - hv->vf_devargs = NULL;
> > -
> > hn_detach(hv);
> > hn_chim_uninit(eth_dev);
> > rte_vmbus_chan_close(hv->channels[0]);
> > @@ -1423,6 +1435,61 @@ eth_hn_dev_uninit(struct rte_eth_dev *eth_dev)
> > return ret_stop;
> > }
> >
> > +static int populate_cache_list(void)
> > +{
> > + int ret;
> > + struct rte_devargs *da;
> > +
> > + rte_spinlock_lock(&netvsc_lock);
> > + da_cache_usage++;
> > + if (da_cache_usage > 1) {
> > + ret = 0;
> > + goto out;
> > + }
> > +
> > + LIST_INIT(&da_cache_list);
> > + RTE_EAL_DEVARGS_FOREACH("pci", da) {
> > + struct da_cache *cache;
> > +
> > + cache = rte_zmalloc("NETVSC-HOTADD", sizeof(*cache),
> rte_mem_page_size());
> > + if (!cache) {
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + strncpy(cache->name, da->name, sizeof(da->name));
> > + cache->drv_str = strdup(da->drv_str);
> > + if (!cache->drv_str) {
> > + rte_free(cache);
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + LIST_INSERT_HEAD(&da_cache_list, cache, list);
> > + }
>
> Why do you need to cache entry to be page aligned, that seems unnecessary
> wasteful?
You are right it doesn't need to. I'm removing the alignment.
> Why does it need to be huge pages? versus normal malloc?
I thought it would make it easier to debug memory leaks through EAL. But normal
malloc is fine because this data is not shared between primary/secondary.
> The string is coming from malloc (strdup) so it can't be used by secondary
> process.
>
> Since you are allocating a devargs cache entry, you could just as well use
> flexible
> array where entry was like:
> struct da_cache {
> LIST_ENTRY(da_cache) list;
> char name[RTE_DEV_NAME_MAX_LEN];
> char drv_str[];
> };
This is difficult as I don't know how big it is for drv_str[].
>
>
> cache = malloc(sizeof(*cache) + strlen(da->drv_str) + 1); ...
> strcpy(cache->drv_str, da->drv_str);
Another approach is to modify EAL to never delete driver arguments when a
device is removed. i.e., It doesn't call rte_devargs_remove() on device
removal, instead keep those devargs for the lifetime of the process. Do you
think this is a better approach? This will save work if other drivers want to
cache devargs list for device hot plug events.
Thanks,
Long
