On Thu, Jul 30, 2015 at 12:11:57PM +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> > --- > v3: > * add refcountin of limit by # vhost devices, > and make vhost_has_free_slot() return true if no vhost devices > are present at current moment > * move limit initialization to vhost_dev_init() > 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 | 23 +++++++++++++++++++++++ > include/hw/virtio/vhost-backend.h | 2 ++ > include/hw/virtio/vhost.h | 1 + > stubs/Makefile.objs | 1 + > stubs/vhost.c | 6 ++++++ > 7 files changed, 60 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..bcbad48 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -26,6 +26,18 @@ > > static struct vhost_log *vhost_log; > > +static struct { > + int used_memslots; > + int memslots_limit; > + int refcount; > +} slots_limit; > + > +bool vhost_has_free_slot(void) > +{ > + return slots_limit.refcount ? > + slots_limit.memslots_limit > slots_limit.used_memslots : true; > +} > + > 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; > + slots_limit.used_memslots = dev->mem->nregions; > } > > static bool vhost_section(MemoryRegionSection *section) > @@ -916,6 +929,14 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > return -errno; > } > > + r = hdev->vhost_ops->vhost_backend_memslots_limit(hdev); > + if (slots_limit.refcount > 0) { > + slots_limit.memslots_limit = MIN(slots_limit.memslots_limit, r); > + } else { > + slots_limit.memslots_limit = r; > + } > + slots_limit.refcount++; > + > r = hdev->vhost_ops->vhost_call(hdev, VHOST_SET_OWNER, NULL); > if (r < 0) { > goto fail; > @@ -972,6 +993,7 @@ fail_vq: > fail: > r = -errno; > hdev->vhost_ops->vhost_backend_cleanup(hdev); > + slots_limit.refcount--; > return r; > } > > @@ -989,6 +1011,7 @@ void vhost_dev_cleanup(struct vhost_dev *hdev) > g_free(hdev->mem); > g_free(hdev->mem_sections); > hdev->vhost_ops->vhost_backend_cleanup(hdev); > + slots_limit.refcount--; > } > > /* Stop processing guest IO notifications in qemu.
This is not enough in case one is mixing vhost user and vhost kernel devices. One has to scan all devices. > 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