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Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log
From: |
Marc-André Lureau |
Subject: |
Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log |
Date: |
Mon, 21 Sep 2015 10:02:02 -0400 (EDT) |
Hi
----- Original Message -----
> On Sat, Sep 19, 2015 at 12:11:58PM +0200, address@hidden wrote:
> > From: Marc-André Lureau <address@hidden>
> >
> > If the backend is of type VHOST_BACKEND_TYPE_USER, allocate
> > shareable memory. Next patch will only allocate when the backend
> > has the required feature.
> >
> > 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>
>
> Well you do at least need to count the number of times the log is
> shared. Otherwise, if you share the log, then unshare it, you are left
> with a shared one.
Do you mean that if the device is removed (or stopped, so that the log is
unref) and a shm log is no longer needed, it should replace the log of other
devices with a non-shm log? In this case, wouldn't it make more sense to have a
log shm per device, because replacing other devices log do not seem simple
without more tracking of devices sharing the log.
Can this be considered a future enhancement?
>
> > ---
> > 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 a08c36b..cd3af16 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);
> > + } else {
> > + log->log = g_malloc0(logsize);
> > + }
> >
> > 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
>
- [Qemu-devel] [PATCH v4 00/22] vhost-user: add migration support, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 01/22] vhost-user: refactor ioctl translation, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 02/22] vhost-user: add protocol feature negotiation, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 03/22] vhost-user: unit test for new messages, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 04/22] configure: probe for memfd, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 05/22] util: add linux-only memfd fallback, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 06/22] util: add memfd helpers, marcandre . lureau, 2015/09/19
- [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, marcandre . lureau, 2015/09/19
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/21
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log,
Marc-André Lureau <=
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/21
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Marc-André Lureau, 2015/09/21
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Marc-André Lureau, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Marc-André Lureau, 2015/09/22
- Re: [Qemu-devel] [PATCH v4 07/22] vhost: alloc shareable log, Michael S. Tsirkin, 2015/09/22
[Qemu-devel] [PATCH v4 08/22] vhost: document log resizing, marcandre . lureau, 2015/09/19
[Qemu-devel] [PATCH v4 09/22] vhost: use a function for each call, marcandre . lureau, 2015/09/19