Re: [PATCH 2/6] vhost: get guest/host physical address mappings

On 08/23/2016 02:32 PM, Yuanhan Liu wrote:

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+	/* FIXME */
+	RTE_LOG(INFO, VHOST_CONFIG, ":: %u ::\n", pre_read);

For my information, what is the purpose of pre_read?

Again, I put a FIXME here, but I forgot to add some explanation.

Here is the thing: the read will make sure the kernel populate the
corresponding PTE entry, so that rte_mem_virt2phy() will return proper
physical address, otherwise, invalid value is returned.

I can't simply do the read but do not actually reference/consume it.
Otherwise, the compiler will treat it as some noops and remove it.

An ugly RTE_LOG will make sure the read operation is not eliminated.
I'm seeking a more proper way to achieve that. Maybe I can add a new
field in virtio_net structure and store it there.

Or, do you have better ideas?

This behavior is pretty twisted, no?
Shouldn't be rte_mem_virt2phy() role to ensure returning a valid value?

I have no better idea for now, but I will think about it.

Regards,
Maxime