On Wed, Dec 02, 2015 at 11:43:11AM +0800, 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.
>
> 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);
I think the atomic OR operation is necessary only if there can be
more than one vhost-user back-end updating the guest's memory
simultaneously. However probably it is pretty safe to perform
regular OR operation, since rings are not shared between
back-end. What about buffers pointed by descriptors? To be on
the safe side, I would use a GCC built-in function
__sync_fetch_and_or().
> +}
> +
> +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;
Isn't "likely" more appropriate in above, since the whole
expression is expected to be true most of the time?
> +
> + 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
