[dpdk-dev] [PATCH 2/4] vhost: introduce vhost_log_write

[Yuanhan Liu]

Introduce vhost_log_write() helper function to log the dirty pages we
touched. Page size is harded code to 4096 (VHOST_LOG_PAGE), and each
log is presented by 1 bit.

Therefore, vhost_log_write() simply finds the right bit for related
page we are gonna change, and set it to 1. dev->log_base denotes the
start of the dirty page bitmap.

The page address is biased by log_guest_addr, which is derived from
SET_VRING_ADDR request as part of the vring related addresses.

Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
---
 lib/librte_vhost/rte_virtio_net.h | 34 ++++++++++++++++++++++++++++++++++
 lib/librte_vhost/virtio-net.c     |  4 ++++
 2 files changed, 38 insertions(+)

diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 416dac2..191c1be 100644
--- a/lib/librte_vhost/rte_virtio_net.h
+++ b/lib/librte_vhost/rte_virtio_net.h
@@ -40,6 +40,7 @@
  */
 
 #include <stdint.h>
+#include <linux/vhost.h>
 #include <linux/virtio_ring.h>
 #include <linux/virtio_net.h>
 #include <sys/eventfd.h>
@@ -59,6 +60,8 @@ struct rte_mbuf;
 /* Backend value set by guest. */
 #define VIRTIO_DEV_STOPPED -1
 
+#define VHOST_LOG_PAGE	4096
+
 
 /* Enum for virtqueue management. */
 enum {VIRTIO_RXQ, VIRTIO_TXQ, VIRTIO_QNUM};
@@ -82,6 +85,7 @@ struct vhost_virtqueue {
 	struct vring_desc	*desc;			/**< Virtqueue descriptor ring. */
 	struct vring_avail	*avail;			/**< Virtqueue available ring. */
 	struct vring_used	*used;			/**< Virtqueue used ring. */
+	uint64_t		log_guest_addr;		/**< Physical address of used ring, for logging */
 	uint32_t		size;			/**< Size of descriptor ring. */
 	uint32_t		backend;		/**< Backend value to determine if device should started/stopped. */
 	uint16_t		vhost_hlen;		/**< Vhost header length (varies depending on RX merge buffers. */
@@ -203,6 +207,36 @@ gpa_to_vva(struct virtio_net *dev, uint64_t guest_pa)
 	return vhost_va;
 }
 
+static inline void __attribute__((always_inline))
+vhost_log_page(uint8_t *log_base, uint64_t page)
+{
+	/* TODO: to make it atomic? */
+	log_base[page / 8] |= 1 << (page % 8);
+}
+
+static inline void __attribute__((always_inline))
+vhost_log_write(struct virtio_net *dev, struct vhost_virtqueue *vq,
+		uint64_t offset, uint64_t len)
+{
+	uint64_t addr = vq->log_guest_addr;
+	uint64_t page;
+
+	if (unlikely(((dev->features & (1ULL << VHOST_F_LOG_ALL)) == 0) ||
+		     !dev->log_base || !len))
+		return;
+
+	addr += offset;
+	if (dev->log_size < ((addr + len - 1) / VHOST_LOG_PAGE / 8))
+		return;
+
+	page = addr / VHOST_LOG_PAGE;
+	while (page * VHOST_LOG_PAGE < addr + len) {
+		vhost_log_page(dev->log_base, page);
+		page += VHOST_LOG_PAGE;
+	}
+}
+
+
 /**
  *  Disable features in feature_mask. Returns 0 on success.
  */
diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c
index 8364938..4481827 100644
--- a/lib/librte_vhost/virtio-net.c
+++ b/lib/librte_vhost/virtio-net.c
@@ -666,12 +666,16 @@ set_vring_addr(struct vhost_device_ctx ctx, struct vhost_vring_addr *addr)
 		return -1;
 	}
 
+	vq->log_guest_addr = addr->log_guest_addr;
+
 	LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") mapped address desc: %p\n",
 			dev->device_fh, vq->desc);
 	LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") mapped address avail: %p\n",
 			dev->device_fh, vq->avail);
 	LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") mapped address used: %p\n",
 			dev->device_fh, vq->used);
+	LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") log_guest_addr: %p\n",
+			dev->device_fh, (void *)(uintptr_t)vq->log_guest_addr);
 
 	return 0;
 }
-- 
1.9.0