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From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
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Date: Thu, 17 Dec 2015 11:11:57 +0800
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Cc: "Michael S. Tsirkin" <mst@redhat.com>,
 Victor Kaplansky <vkaplans@redhat.com>
Subject: [dpdk-dev] [PATCH v2 2/6] vhost: introduce vhost_log_write
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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.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Victor Kaplansky <victork@redhat.com
---
 lib/librte_vhost/rte_virtio_net.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 8acee02..5726683 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};
@@ -205,6 +208,32 @@ 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)
+{
+	log_base[page / 8] |= 1 << (page % 8);
+}
+
+static inline void __attribute__((always_inline))
+vhost_log_write(struct virtio_net *dev, uint64_t addr, uint64_t len)
+{
+	uint64_t page;
+
+	if (likely(((dev->features & (1ULL << VHOST_F_LOG_ALL)) == 0) ||
+		   !dev->log_base || !len))
+		return;
+
+	if (unlikely(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((uint8_t *)(uintptr_t)dev->log_base, page);
+		page += VHOST_LOG_PAGE;
+	}
+}
+
+
 /**
  *  Disable features in feature_mask. Returns 0 on success.
  */
-- 
1.9.0