Re: [Qemu-devel] [PATCH v2 42/45] ivshmem: add hostmem backend

[Andrew Jones <drjones@redhat.com>]

On Tue, Jul 28, 2015 at 02:32:54AM +0200, Marc-André Lureau wrote:
> From: Marc-André Lureau <marcandre.lureau@gmail.com>
> 
> Instead of handling allocation, teach ivshmem to use a memory backend.
> This allows to use hugetlbfs backed memory now.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  hw/misc/ivshmem.c    | 85 ++++++++++++++++++++++++++++++++++++++++------------
>  tests/ivshmem-test.c | 12 ++++++++
>  2 files changed, 78 insertions(+), 19 deletions(-)
> 
> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> index ecf31f9..a150500 100644
> --- a/hw/misc/ivshmem.c
> +++ b/hw/misc/ivshmem.c
> @@ -26,6 +26,8 @@
>  #include "qemu/event_notifier.h"
>  #include "qemu/fifo8.h"
>  #include "sysemu/char.h"
> +#include "sysemu/hostmem.h"
> +#include "qapi/visitor.h"
>  
>  #include "hw/misc/ivshmem.h"
>  
> @@ -57,6 +59,8 @@
>  #define IVSHMEM(obj) \
>      OBJECT_CHECK(IVShmemState, (obj), TYPE_IVSHMEM)
>  
> +#define IVSHMEM_MEMDEV_PROP "memdev"
> +
>  typedef struct Peer {
>      int nb_eventfds;
>      EventNotifier *eventfds;
> @@ -72,6 +76,7 @@ typedef struct IVShmemState {
>      PCIDevice parent_obj;
>      /*< public >*/
>  
> +    HostMemoryBackend *hostmem;
>      uint32_t intrmask;
>      uint32_t intrstatus;
>  
> @@ -700,9 +705,23 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
>          PCI_BASE_ADDRESS_MEM_PREFETCH;;
>      Error *local_err = NULL;
>  
> -    s->shm_fd = -1;
> +    if (!!s->server_chr + !!s->shmobj + !!s->hostmem != 1) {
> +        error_setg(errp, "You must specify either a shmobj, a chardev"
> +                   " or a hostmem");
> +        return;
> +    }
> +
> +    if (s->hostmem) {
> +        MemoryRegion *mr;
>  
> -    if (s->sizearg == NULL) {
> +        if (s->sizearg) {
> +            error_setg(errp, "hostmem requires no size argument");
> +            return;
Just warn instead? "size argument ignored with hostmem" Otherwise
"hostmem must not specify a size argument" would be more clear
> +        }
> +
> +        mr = host_memory_backend_get_memory(s->hostmem, errp);
> +        s->ivshmem_size = memory_region_size(mr);
> +    } else if (s->sizearg == NULL) {
>          s->ivshmem_size = 4 << 20; /* 4 MB default */
>      } else {
>          s->ivshmem_size = parse_mem_size(s->sizearg, &local_err);
> @@ -758,7 +777,16 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
>          attr |= PCI_BASE_ADDRESS_MEM_TYPE_64;
>      }
>  
> -    if (s->server_chr != NULL) {
> +    if (s->hostmem != NULL) {
> +        MemoryRegion *mr;
> +
> +        IVSHMEM_DPRINTF("using hostmem\n");
> +
> +        mr = host_memory_backend_get_memory(MEMORY_BACKEND(s->hostmem), errp);
> +        vmstate_register_ram(mr, DEVICE(s));
> +        memory_region_add_subregion(&s->bar, 0, mr);
> +        pci_register_bar(PCI_DEVICE(s), 2, attr, &s->bar);
> +    } else if (s->server_chr != NULL) {
>          if (strncmp(s->server_chr->filename, "unix:", 5)) {
>              error_setg(errp, "chardev is not a unix client socket");
>              return;
> @@ -767,12 +795,6 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
>          /* if we get a UNIX socket as the parameter we will talk
>           * to the ivshmem server to receive the memory region */
>  
> -        if (s->shmobj != NULL) {
> -            error_setg(errp, "do not specify both 'chardev' "
> -                       "and 'shm' with ivshmem");
> -            return;
> -        }
> -
>          IVSHMEM_DPRINTF("using shared memory server (socket = %s)\n",
>                          s->server_chr->filename);
>  
> @@ -796,11 +818,6 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error **errp)
>          /* just map the file immediately, we're not using a server */
>          int fd;
>  
> -        if (s->shmobj == NULL) {
> -            error_setg(errp, "Must specify 'chardev' or 'shm' to ivshmem");
> -            return;
> -        }
> -
>          IVSHMEM_DPRINTF("using shm_open (shm object = %s)\n", s->shmobj);
>  
>          /* try opening with O_EXCL and if it succeeds zero the memory
> @@ -840,14 +857,17 @@ static void pci_ivshmem_exit(PCIDevice *dev)
>      }
>  
>      if (memory_region_is_mapped(&s->ivshmem)) {
> -        void *addr = memory_region_get_ram_ptr(&s->ivshmem);
> +        if (!s->hostmem) {
> +            void *addr = memory_region_get_ram_ptr(&s->ivshmem);
> +
> +            if (munmap(addr, s->ivshmem_size) == -1) {
> +                error_report("Failed to munmap shared memory %s",
> +                             strerror(errno));
> +            }
> +        }
>  
>          vmstate_unregister_ram(&s->ivshmem, DEVICE(dev));
>          memory_region_del_subregion(&s->bar, &s->ivshmem);
> -
> -        if (munmap(addr, s->ivshmem_size) == -1) {
> -            error_report("Failed to munmap shared memory %s", strerror(errno));
> -        }
>      }
>  
>      if (s->eventfd_chr) {
> @@ -955,10 +975,37 @@ static void ivshmem_class_init(ObjectClass *klass, void *data)
>      dc->desc = "Inter-VM shared memory";
>  }
>  
> +static void ivshmem_check_memdev_is_busy(Object *obj, const char *name,
> +                                         Object *val, Error **errp)
> +{
> +    MemoryRegion *mr;
> +
> +    mr = host_memory_backend_get_memory(MEMORY_BACKEND(val), errp);
> +    if (memory_region_is_mapped(mr)) {
> +        char *path = object_get_canonical_path_component(val);
> +        error_setg(errp, "can't use already busy memdev: %s", path);
> +        g_free(path);
> +    } else {
> +        qdev_prop_allow_set_link_before_realize(obj, name, val, errp);
> +    }
> +}
> +
> +static void ivshmem_init(Object *obj)
> +{
> +    IVShmemState *s = IVSHMEM(obj);
> +
> +    object_property_add_link(obj, IVSHMEM_MEMDEV_PROP, TYPE_MEMORY_BACKEND,
> +                             (Object **)&s->hostmem,
> +                             ivshmem_check_memdev_is_busy,
> +                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
> +                             &error_abort);
> +}
> +
>  static const TypeInfo ivshmem_info = {
>      .name          = TYPE_IVSHMEM,
>      .parent        = TYPE_PCI_DEVICE,
>      .instance_size = sizeof(IVShmemState),
> +    .instance_init = ivshmem_init,
>      .class_init    = ivshmem_class_init,
>  };
>  
> diff --git a/tests/ivshmem-test.c b/tests/ivshmem-test.c
> index 03f44c1..920b9fa 100644
> --- a/tests/ivshmem-test.c
> +++ b/tests/ivshmem-test.c
> @@ -390,6 +390,17 @@ static void test_ivshmem_hotplug(void)
>      g_free(opts);
>  }
>  
> +static void test_ivshmem_memdev(void)
> +{
> +    IVState state;
> +
> +    /* just for the sake of checking memory-backend property */
> +    setup_vm_cmd(&state, "-object memory-backend-ram,size=1M,id=mb1"
> +                 " -device ivshmem,memdev=mb1", false);
> +
> +    qtest_quit(state.qtest);
> +}
> +
>  static void cleanup(void)
>  {
>      if (tmpshmem) {
> @@ -466,6 +477,7 @@ int main(int argc, char **argv)
>      qtest_add_func("/ivshmem/pair", test_ivshmem_pair);
>      qtest_add_func("/ivshmem/server", test_ivshmem_server);
>      qtest_add_func("/ivshmem/hotplug", test_ivshmem_hotplug);
> +    qtest_add_func("/ivshmem/memdev", test_ivshmem_memdev);
>  
>      ret = g_test_run();
>  
> -- 
> 2.4.3
> 
> 

Thanks,
drew