[dpdk-dev] [PATCH 2/6] vhost: get guest/host physical address mappings

[Yuanhan Liu]

On Tue, Aug 23, 2016 at 11:58:42AM +0200, Maxime Coquelin wrote:
> >
> >+/* Convert guest physical address to host physical address */
> >+static inline phys_addr_t __attribute__((always_inline))
> >+gpa_to_hpa(struct virtio_net *dev, uint64_t gpa, uint64_t size)
> >+{
> >+	uint32_t i;
> >+	struct guest_page *page;
> >+
> >+	for (i = 0; i < dev->nr_guest_pages; i++) {
> >+		page = &dev->guest_pages[i];
> >+
> >+		if (gpa >= page->guest_phys_addr &&
> >+		    gpa + size < page->guest_phys_addr + page->size) {
> Shouldn't be '<=' here?

Oops, you are right.

> >+			return gpa - page->guest_phys_addr +
> >+			       page->host_phys_addr;
> >+		}
> >+	}
> >+
> >+	return 0;
> >+}
> >+
> > struct virtio_net_device_ops const *notify_ops;
> > struct virtio_net *get_device(int vid);
> >
> >diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> >index d2071fd..045d4f0 100644
> >--- a/lib/librte_vhost/vhost_user.c
> >+++ b/lib/librte_vhost/vhost_user.c
> >@@ -372,6 +372,81 @@ vhost_user_set_vring_base(struct virtio_net *dev,
> > 	return 0;
> > }
> >
> >+static void
> >+add_one_guest_page(struct virtio_net *dev, uint64_t guest_phys_addr,
> >+		   uint64_t host_phys_addr, uint64_t size)
> >+{
> >+	struct guest_page *page;
> >+
> >+	if (dev->nr_guest_pages == dev->max_guest_pages) {
> >+		dev->max_guest_pages *= 2;
> >+		dev->guest_pages = realloc(dev->guest_pages,
> >+					dev->max_guest_pages * sizeof(*page));
> 
> Maybe realloc return could be checked?

Yes, I should have done that. Besides, I also forgot to free it at
somewhere. Will fix it.

> 
> >+	}
> >+
> >+	page = &dev->guest_pages[dev->nr_guest_pages++];
> >+	page->guest_phys_addr = guest_phys_addr;
> >+	page->host_phys_addr  = host_phys_addr;
> >+	page->size = size;
> >+}
> >+
> >+static void
> >+add_guest_pages(struct virtio_net *dev, struct virtio_memory_region *reg,
> >+		uint64_t page_size)
> >+{
> >+	uint64_t reg_size = reg->size;
> >+	uint64_t host_user_addr  = reg->host_user_addr;
> >+	uint64_t guest_phys_addr = reg->guest_phys_addr;
> >+	uint64_t host_phys_addr;
> >+	uint64_t size;
> >+	uint32_t pre_read;
> >+
> >+	pre_read = *((uint32_t *)(uintptr_t)host_user_addr);
> >+	host_phys_addr = rte_mem_virt2phy((void *)(uintptr_t)host_user_addr);
> >+	size = page_size - (guest_phys_addr & (page_size - 1));
> >+	size = RTE_MIN(size, reg_size);
> >+
> >+	add_one_guest_page(dev, guest_phys_addr, host_phys_addr, size);
> >+	host_user_addr  += size;
> >+	guest_phys_addr += size;
> >+	reg_size -= size;
> >+
> >+	while (reg_size > 0) {
> >+		pre_read += *((uint32_t *)(uintptr_t)host_user_addr);
> >+		host_phys_addr = rte_mem_virt2phy((void *)(uintptr_t)host_user_addr);
> >+		add_one_guest_page(dev, guest_phys_addr, host_phys_addr, page_size);
> >+
> >+		host_user_addr  += page_size;
> >+		guest_phys_addr += page_size;
> >+		reg_size -= page_size;
> >+	}
> >+
> >+	/* 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?

	--yliu