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Re: [Qemu-devel] [PATCH v2 4/9] vhost: alloc shareable log
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v2 4/9] vhost: alloc shareable log |
Date: |
Wed, 29 Jul 2015 17:53:26 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
* Marc-André Lureau (address@hidden) wrote:
> If the backend is of type VHOST_BACKEND_TYPE_USER, allocate
> shareable memory.
>
> Note: vhost_log_get() can use a global "vhost_log" that can be shared by
> several vhost devices. We may want instead a common shareable log and a
> common non-shareable one.
>
> Signed-off-by: Marc-André Lureau <address@hidden>
> ---
> hw/virtio/vhost.c | 38 +++++++++++++++++++++++++++++++-------
> include/hw/virtio/vhost.h | 3 ++-
> 2 files changed, 33 insertions(+), 8 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 2712c6f..862e786 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -18,6 +18,7 @@
> #include "qemu/atomic.h"
> #include "qemu/range.h"
> #include "qemu/error-report.h"
> +#include "qemu/memfd.h"
> #include <linux/vhost.h>
> #include "exec/address-spaces.h"
> #include "hw/virtio/virtio-bus.h"
> @@ -286,20 +287,34 @@ static uint64_t vhost_get_log_size(struct vhost_dev
> *dev)
> }
> return log_size;
> }
> -static struct vhost_log *vhost_log_alloc(uint64_t size)
> +
> +static struct vhost_log *vhost_log_alloc(uint64_t size, bool share)
> {
> - struct vhost_log *log = g_malloc0(sizeof *log + size *
> sizeof(*(log->log)));
> + struct vhost_log *log;
> + uint64_t logsize = size * sizeof(*(log->log));
> + int fd = -1;
> +
> + log = g_new0(struct vhost_log, 1);
> + if (share) {
> + log->log = qemu_memfd_alloc("vhost-log", logsize,
> + F_SEAL_GROW|F_SEAL_SHRINK|F_SEAL_SEAL,
> &fd);
> + memset(log->log, 0, logsize);
qemu_memfd_alloc can return NULL can't it - so that needs checking?
> + } else {
> + log->log = g_malloc0(logsize);
I know the old code also used g_malloc0, but if the log isn't 'small'
then g_try_malloc0 is possibly safer and properly return errors
if it can't be allocated.
Dave
> + }
>
> log->size = size;
> log->refcnt = 1;
> + log->fd = fd;
>
> return log;
> }
>
> -static struct vhost_log *vhost_log_get(uint64_t size)
> +static struct vhost_log *vhost_log_get(uint64_t size, bool share)
> {
> - if (!vhost_log || vhost_log->size != size) {
> - vhost_log = vhost_log_alloc(size);
> + if (!vhost_log || vhost_log->size != size ||
> + (share && vhost_log->fd == -1)) {
> + vhost_log = vhost_log_alloc(size, share);
> } else {
> ++vhost_log->refcnt;
> }
> @@ -324,13 +339,21 @@ static void vhost_log_put(struct vhost_dev *dev, bool
> sync)
> if (vhost_log == log) {
> vhost_log = NULL;
> }
> +
> + if (log->fd == -1) {
> + g_free(log->log);
> + } else {
> + qemu_memfd_free(log->log, log->size * sizeof(*(log->log)),
> + log->fd);
> + }
> g_free(log);
> }
> }
>
> static inline void vhost_dev_log_resize(struct vhost_dev* dev, uint64_t size)
> {
> - struct vhost_log *log = vhost_log_get(size);
> + bool share = dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_USER;
> + struct vhost_log *log = vhost_log_get(size, share);
> uint64_t log_base = (uintptr_t)log->log;
> int r;
>
> @@ -1136,9 +1159,10 @@ int vhost_dev_start(struct vhost_dev *hdev,
> VirtIODevice *vdev)
>
> if (hdev->log_enabled) {
> uint64_t log_base;
> + bool share = hdev->vhost_ops->backend_type ==
> VHOST_BACKEND_TYPE_USER;
>
> hdev->log_size = vhost_get_log_size(hdev);
> - hdev->log = vhost_log_get(hdev->log_size);
> + hdev->log = vhost_log_get(hdev->log_size, share);
> log_base = (uintptr_t)hdev->log->log;
> r = hdev->vhost_ops->vhost_call(hdev, VHOST_SET_LOG_BASE,
> hdev->log_size ? &log_base : NULL);
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index 6467c73..ab1dcac 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -31,7 +31,8 @@ typedef unsigned long vhost_log_chunk_t;
> struct vhost_log {
> unsigned long long size;
> int refcnt;
> - vhost_log_chunk_t log[0];
> + int fd;
> + vhost_log_chunk_t *log;
> };
>
> struct vhost_memory;
> --
> 2.4.3
>
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH v2 0/9] vhost-user: add migration log support (for 2.5), Marc-André Lureau, 2015/07/28
- [Qemu-devel] [PATCH v2 5/9] vhost: document log resizing, Marc-André Lureau, 2015/07/28
- [Qemu-devel] [PATCH v2 6/9] vhost: use variable arguments for vhost_call(), Marc-André Lureau, 2015/07/28
- [Qemu-devel] [PATCH v2 7/9] vhost-user: start and end the va_list, Marc-André Lureau, 2015/07/28
- [Qemu-devel] [PATCH v2 8/9] vhost-user: send log shm fd along with log_base, Marc-André Lureau, 2015/07/28
- [Qemu-devel] [PATCH v2 9/9] vhost-user: document migration log, Marc-André Lureau, 2015/07/28