[dpdk-dev] [PATCH v2 2/6] vhost: introduce vhost_log_write

Xie, Huawei huawei.xie at intel.com
Mon Dec 21 16:06:43 CET 2015


On 12/17/2015 11:11 AM, Yuanhan Liu wrote:
> 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
> ---
>  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);
> +}
> +
Those logging functions are not supposed to be API. Could we move them
into an internal header file?
> +static inline void __attribute__((always_inline))
> +vhost_log_write(struct virtio_net *dev, uint64_t addr, uint64_t len)
> +{
> +	uint64_t page;
> +
Before we log, we need memory barrier to make sure updates are in place.
> +	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) {
Let us have a page_end var to make the code simpler?
> +		vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, page);
> +		page += VHOST_LOG_PAGE;
page += 1?
> +	}
> +}
> +
> +
>  /**
>   *  Disable features in feature_mask. Returns 0 on success.
>   */



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