[dpdk-dev] [PATCH v3 2/8] 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.

Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
Signed-off-by: Victor Kaplansky <victork at redhat.com>
Tested-by: Pavel Fedin <p.fedin at samsung.com>
---

v3: - move the two functions inside vhost_rxtx.c

    - add a memory barrier before logging, to make sure guest memory
      updates are committed before logging.

    - Fix an off-by-one bug
---
 lib/librte_vhost/rte_virtio_net.h |  2 ++
 lib/librte_vhost/vhost_rxtx.c     | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 8acee02..2c891ae 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>
@@ -205,6 +206,7 @@ gpa_to_vva(struct virtio_net *dev, uint64_t guest_pa)
 	return vhost_va;
 }
 
+
 /**
  *  Disable features in feature_mask. Returns 0 on success.
  */
diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index bbf3fac..d485364 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -42,6 +42,35 @@
 #include "vhost-net.h"
 
 #define MAX_PKT_BURST 32
+#define VHOST_LOG_PAGE	4096
+
+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;
+
+	/* To make sure guest memory updates are committed before logging */
+	rte_smp_wmb();
+
+	page = addr / VHOST_LOG_PAGE;
+	while (page * VHOST_LOG_PAGE < addr + len) {
+		vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, page);
+		page += 1;
+	}
+}
 
 static bool
 is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t qp_nb)
-- 
1.9.0