On Wed, 29 Jul 2015 18:11:14 +0300 "Michael S. Tsirkin" <m...@redhat.com> wrote:
> On Wed, Jul 29, 2015 at 01:49:48PM +0200, Igor Mammedov wrote: > > it will allow for other parts of QEMU check if it's safe > > to map memory region during hotplug/runtime. > > That way hotplug path will have a chance to cancel > > hotplug operation instead of crashing in vhost_commit(). > > > > Signed-off-by: Igor Mammedov <imamm...@redhat.com> > > --- > > v2: > > * replace probbing with checking for > > /sys/module/vhost/parameters/max_mem_regions and > > if it's missing has non wrong value return > > hardcoded legacy limit (64 slots). > > --- > > hw/virtio/vhost-backend.c | 21 ++++++++++++++++++++- > > hw/virtio/vhost-user.c | 8 +++++++- > > hw/virtio/vhost.c | 21 +++++++++++++++++++++ > > include/hw/virtio/vhost-backend.h | 2 ++ > > include/hw/virtio/vhost.h | 1 + > > stubs/Makefile.objs | 1 + > > stubs/vhost.c | 6 ++++++ > > 7 files changed, 58 insertions(+), 2 deletions(-) > > create mode 100644 stubs/vhost.c > > > > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c > > index 4d68a27..11ec669 100644 > > --- a/hw/virtio/vhost-backend.c > > +++ b/hw/virtio/vhost-backend.c > > @@ -11,6 +11,7 @@ > > #include "hw/virtio/vhost.h" > > #include "hw/virtio/vhost-backend.h" > > #include "qemu/error-report.h" > > +#include "linux/vhost.h" > > > > #include <sys/ioctl.h> > > > > @@ -42,11 +43,29 @@ static int vhost_kernel_cleanup(struct vhost_dev *dev) > > return close(fd); > > } > > > > +static int vhost_kernel_memslots_limit(struct vhost_dev *dev) > > +{ > > + int limit = 64; > > + char *s; > > + > > + if (g_file_get_contents("/sys/module/vhost/parameters/max_mem_regions", > > + &s, NULL, NULL)) { > > + uint64_t val = g_ascii_strtoull(s, NULL, 10); > > + if (!((val == G_MAXUINT64 || !val) && errno)) { > > + return val; > > + } > > + error_report("ignoring invalid max_mem_regions value in vhost > > module:" > > + " %s", s); > > + } > > + return limit; > > +} > > + > > static const VhostOps kernel_ops = { > > .backend_type = VHOST_BACKEND_TYPE_KERNEL, > > .vhost_call = vhost_kernel_call, > > .vhost_backend_init = vhost_kernel_init, > > - .vhost_backend_cleanup = vhost_kernel_cleanup > > + .vhost_backend_cleanup = vhost_kernel_cleanup, > > + .vhost_backend_memslots_limit = vhost_kernel_memslots_limit > > }; > > > > int vhost_set_backend_type(struct vhost_dev *dev, VhostBackendType > > backend_type) > > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > > index e7ab829..acdfd04 100644 > > --- a/hw/virtio/vhost-user.c > > +++ b/hw/virtio/vhost-user.c > > @@ -343,9 +343,15 @@ static int vhost_user_cleanup(struct vhost_dev *dev) > > return 0; > > } > > > > +static int vhost_user_memslots_limit(struct vhost_dev *dev) > > +{ > > + return VHOST_MEMORY_MAX_NREGIONS; > > +} > > + > > const VhostOps user_ops = { > > .backend_type = VHOST_BACKEND_TYPE_USER, > > .vhost_call = vhost_user_call, > > .vhost_backend_init = vhost_user_init, > > - .vhost_backend_cleanup = vhost_user_cleanup > > + .vhost_backend_cleanup = vhost_user_cleanup, > > + .vhost_backend_memslots_limit = vhost_user_memslots_limit > > }; > > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > > index 2712c6f..e964004 100644 > > --- a/hw/virtio/vhost.c > > +++ b/hw/virtio/vhost.c > > @@ -26,6 +26,18 @@ > > > > static struct vhost_log *vhost_log; > > > > +static int used_memslots; > > +static int memslots_limit = -1; > > I suspect this need to be in some structure, refcounted by vhost devices > using it. vhost_kernel_memslots_limit would then be called when 1st > vhost device is added. vhost_kernel_memslots_limit() should be called for every added vhost device, since mixed vhost backends may have different limit. refcounting might help with disabling limit check when all vhost devices are hot-unplugged and user will be able to plug in more memory and won't be able to add vhost device with lower limit. but I see such usecase highly not probable, hence it's considered adding refcounting as over-engineered way. > > > + > > +bool vhost_has_free_slot(void) > > +{ > > + if (memslots_limit >= 0) { > > + return memslots_limit > used_memslots; > > + } > > + > > + return true; > > Pls rewrite this using logic operators. > Something like > return memslots_limit < 0 || memslots_limit > used_memslots; ? sure > > > +} > > + > > static void vhost_dev_sync_region(struct vhost_dev *dev, > > MemoryRegionSection *section, > > uint64_t mfirst, uint64_t mlast, > > @@ -457,6 +469,7 @@ static void vhost_set_memory(MemoryListener *listener, > > dev->mem_changed_start_addr = MIN(dev->mem_changed_start_addr, > > start_addr); > > dev->mem_changed_end_addr = MAX(dev->mem_changed_end_addr, start_addr > > + size - 1); > > dev->memory_changed = true; > > + used_memslots = dev->mem->nregions; > > } > > > > static bool vhost_section(MemoryRegionSection *section) > > @@ -1119,6 +1132,14 @@ int vhost_dev_start(struct vhost_dev *hdev, > > VirtIODevice *vdev) > > if (r < 0) { > > goto fail_features; > > } > > + > > + r = hdev->vhost_ops->vhost_backend_memslots_limit(hdev); > > + if (memslots_limit > 0) { > > + memslots_limit = MIN(memslots_limit, r); > > + } else { > > + memslots_limit = r; > > + } > > + > > r = hdev->vhost_ops->vhost_call(hdev, VHOST_SET_MEM_TABLE, hdev->mem); > > if (r < 0) { > > r = -errno; > > Doing stuff on start but not stop is almost always a mistake. > In this case, when all vhost devices go away, one can > add more memory again, right? yep, it's possible provided vhost_call(VHOST_SET_MEM_TABLE) succeeds, if it's not then device addition fails gracefully. > > > diff --git a/include/hw/virtio/vhost-backend.h > > b/include/hw/virtio/vhost-backend.h > > index e472f29..28b6714 100644 > > --- a/include/hw/virtio/vhost-backend.h > > +++ b/include/hw/virtio/vhost-backend.h > > @@ -24,12 +24,14 @@ typedef int (*vhost_call)(struct vhost_dev *dev, > > unsigned long int request, > > void *arg); > > typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque); > > typedef int (*vhost_backend_cleanup)(struct vhost_dev *dev); > > +typedef int (*vhost_backend_memslots_limit)(struct vhost_dev *dev); > > > > typedef struct VhostOps { > > VhostBackendType backend_type; > > vhost_call vhost_call; > > vhost_backend_init vhost_backend_init; > > vhost_backend_cleanup vhost_backend_cleanup; > > + vhost_backend_memslots_limit vhost_backend_memslots_limit; > > } VhostOps; > > > > extern const VhostOps user_ops; > > diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h > > index dd51050..17ff7b6 100644 > > --- a/include/hw/virtio/vhost.h > > +++ b/include/hw/virtio/vhost.h > > @@ -81,4 +81,5 @@ uint64_t vhost_get_features(struct vhost_dev *hdev, const > > int *feature_bits, > > uint64_t features); > > void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits, > > uint64_t features); > > +bool vhost_has_free_slot(void); > > #endif > > diff --git a/stubs/Makefile.objs b/stubs/Makefile.objs > > index 9937a12..d2f1b21 100644 > > --- a/stubs/Makefile.objs > > +++ b/stubs/Makefile.objs > > @@ -38,3 +38,4 @@ stub-obj-$(CONFIG_WIN32) += fd-register.o > > stub-obj-y += cpus.o > > stub-obj-y += kvm.o > > stub-obj-y += qmp_pc_dimm_device_list.o > > +stub-obj-y += vhost.o > > diff --git a/stubs/vhost.c b/stubs/vhost.c > > new file mode 100644 > > index 0000000..d346b85 > > --- /dev/null > > +++ b/stubs/vhost.c > > @@ -0,0 +1,6 @@ > > +#include "hw/virtio/vhost.h" > > + > > +bool vhost_has_free_slot(void) > > +{ > > + return true; > > +} > > -- > > 1.8.3.1