On 2022/02/26 17:37, Vladislav Yaroshchuk wrote:
>
> Hi Akihiko,
>
> On Fri, Feb 25, 2022 at 8:46 PM Akihiko Odaki <akihiko.odaki@gmail.com
> <mailto:akihiko.odaki@gmail.com>> wrote:
>
> On 2022/02/26 2:13, Vladislav Yaroshchuk wrote:
> > Interaction with vmnet.framework in different modes
> > differs only on configuration stage, so we can create
> > common `send`, `receive`, etc. procedures and reuse them.
> >
> > vmnet.framework supports iov, but writing more than
> > one iov into vmnet interface fails with
> > 'VMNET_INVALID_ARGUMENT'. Collecting provided iovs into
> > one and passing it to vmnet works fine. That's the
> > reason why receive_iov() left unimplemented. But it still
> > works with good enough performance having .receive()
> > net/vmnet: implement shared mode (vmnet-shared)
> >
> > Interaction with vmnet.framework in different modes
> > differs only on configuration stage, so we can create
> > common `send`, `receive`, etc. procedures and reuse them.
> >
> > vmnet.framework supports iov, but writing more than
> > one iov into vmnet interface fails with
> > 'VMNET_INVALID_ARGUMENT'. Collecting provided iovs into
> > one and passing it to vmnet works fine. That's the
> > reason why receive_iov() left unimplemented. But it still
> > works with good enough performance having .receive()
> > implemented only.
> >
> > Also, there is no way to unsubscribe from vmnet packages
> > receiving except registering and unregistering event
> > callback or simply drop packages just ignoring and
> > not processing them when related flag is set. Here we do
> > using the second way.
> >
> > Signed-off-by: Phillip Tennen <phillip@axleos.com
> <mailto:phillip@axleos.com>>
> > Signed-off-by: Vladislav Yaroshchuk
> <Vladislav.Yaroshchuk@jetbrains.com
> <mailto:Vladislav.Yaroshchuk@jetbrains.com>>
>
> Thank you for persistently working on this.
>
> > ---
> > net/vmnet-common.m | 302
> +++++++++++++++++++++++++++++++++++++++++++++
> > net/vmnet-shared.c | 94 +++++++++++++-
> > net/vmnet_int.h | 39 +++++-
> > 3 files changed, 430 insertions(+), 5 deletions(-)
> >
> > diff --git a/net/vmnet-common.m b/net/vmnet-common.m
> > index 56612c72ce..2f70921cae 100644
> > --- a/net/vmnet-common.m
> > +++ b/net/vmnet-common.m
> > @@ -10,6 +10,8 @@
> > */
> >
> > #include "qemu/osdep.h"
> > +#include "qemu/main-loop.h"
> > +#include "qemu/log.h"
> > #include "qapi/qapi-types-net.h"
> > #include "vmnet_int.h"
> > #include "clients.h"
> > @@ -17,4 +19,304 @@
> > #include "qapi/error.h"
> >
> > #include <vmnet/vmnet.h>
> > +#include <dispatch/dispatch.h>
> >
> > +
> > +static inline void vmnet_set_send_bh_scheduled(VmnetCommonState *s,
> > + bool enable)
> > +{
> > + qatomic_set(&s->send_scheduled, enable);
> > +}
> > +
> > +
> > +static inline bool vmnet_is_send_bh_scheduled(VmnetCommonState *s)
> > +{
> > + return qatomic_load_acquire(&s->send_scheduled);
> > +}
> > +
> > +
> > +static inline void vmnet_set_send_enabled(VmnetCommonState *s,
> > + bool enable)
> > +{
> > + if (enable) {
> > + vmnet_interface_set_event_callback(
> > + s->vmnet_if,
> > + VMNET_INTERFACE_PACKETS_AVAILABLE,
> > + s->if_queue,
> > + ^(interface_event_t event_id, xpc_object_t event) {
> > + assert(event_id ==
> VMNET_INTERFACE_PACKETS_AVAILABLE);
> > + /*
> > + * This function is being called from a non qemu
> thread, so
> > + * we only schedule a BH, and do the rest of the
> io completion
> > + * handling from vmnet_send_bh() which runs in a
> qemu context.
> > + *
> > + * Avoid scheduling multiple bottom halves
> > + */
> > + if (!vmnet_is_send_bh_scheduled(s)) {
> > + vmnet_set_send_bh_scheduled(s, true);
>
> It can be interrupted between vmnet_is_send_bh_scheduled and
> vmnet_set_send_bh_scheduled, which leads to data race.
>
>
> Sorry, I did not clearly understand what you meant. Since this
> callback (block) is submitted on DISPATCH_QUEUE_SERIAL,
> only one instance of the callback will be executed at any
> moment of time.
> https://developer.apple.com/documentation/dispatch/dispatch_queue_serial
> <https://developer.apple.com/documentation/dispatch/dispatch_queue_serial>
>
> Also this is the only place where we schedule a bottom half.
>
> After we set the 'send_scheduled' flag, all the other
> callback blocks will do nothing (skip the if block) until
> the bottom half is executed and reset 'send_scheduled'.
> I don't see any races here :(
>
> Correct me if I'm wrong please.
My explanation that the interruption between vmnet_is_send_bh_scheduled
and vmnet_set_send_bh_scheduled is problematic was actually misleading.
The problem is that vmnet_send_bh resets 'send_scheduled' after calling
vmnet_read. If we got another packet after vmnet_read, it would be
silently ignored.
By the way, I forgot to mention another problem: vmnet_send_completed
calls vmnet_set_send_enabled, but the other packets in the buffer may
not be sent yet. Also, unregistering callbacks in vmnet_set_send_enabled
is probably not enough to stop the callback being fired since some
dispatch blocks are already in the dispatch queue.
Now I understand what you mean, thanks.
What do you think about the workaround? For me
it is quite difficult question how to synchronize qemu with
vmnet thread, especially with completion callback.
Regards,
Akihiko Odaki
>
> > + qemu_bh_schedule(s->send_bh);
> > + }
> > + });
> > + } else {
> > + vmnet_interface_set_event_callback(
> > + s->vmnet_if,
> > + VMNET_INTERFACE_PACKETS_AVAILABLE,
> > + NULL,
> > + NULL);
> > + }
> > +}
> > +
> > +
> > +static void vmnet_send_completed(NetClientState *nc, ssize_t len)
> > +{
> > + VmnetCommonState *s = DO_UPCAST(VmnetCommonState, nc, nc);
> > + vmnet_set_send_enabled(s, true);
> > +}
> > +
> > +
> > +static void vmnet_send_bh(void *opaque)
> > +{
> > + NetClientState *nc = (NetClientState *) opaque;
> > + VmnetCommonState *s = DO_UPCAST(VmnetCommonState, nc, nc);
> > +
> > + struct iovec *iov = s->iov_buf;
> > + struct vmpktdesc *packets = s->packets_buf;
> > + int pkt_cnt;
> > + int i;
> > +
> > + vmnet_return_t status;
> > + ssize_t size;
> > +
> > + /* read as many packets as present */
> > + pkt_cnt = VMNET_PACKETS_LIMIT;
>
> There could be more than VMNET_PACKETS_LIMIT. You may call
> vmnet_read in
> a loop.
>
> > + for (i = 0; i < pkt_cnt; ++i) {
> > + packets[i].vm_pkt_size = s->max_packet_size;
> > + packets[i].vm_pkt_iovcnt = 1;
> > + packets[i].vm_flags = 0;
> > + }
> > +
> > + status = vmnet_read(s->vmnet_if, packets, &pkt_cnt);
> > + if (status != VMNET_SUCCESS) {
> > + error_printf("vmnet: read failed: %s\n",
> > + vmnet_status_map_str(status));
> > + goto done;
> > + }
> > +
> > + for (i = 0; i < pkt_cnt; ++i) {
> > + size = qemu_send_packet_async(nc,
> > + iov[i].iov_base,
> > + packets[i].vm_pkt_size,
> > + vmnet_send_completed);
> > + if (size == 0) {
> > + vmnet_set_send_enabled(s, false);
> > + goto done;
> > + } else if (size < 0) {
> > + break;
> > + }
>
> goto is not needed here. "break" when size <= 0.
>
> > + }
> > +
> > +done:
> > + vmnet_set_send_bh_scheduled(s, false);
> > +}
> > +
> > +
> > +static void vmnet_bufs_init(VmnetCommonState *s)
> > +{
> > + struct vmpktdesc *packets = s->packets_buf;
> > + struct iovec *iov = s->iov_buf;
> > + int i;
> > +
> > + for (i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
> > + iov[i].iov_len = s->max_packet_size;
> > + iov[i].iov_base = g_malloc0(iov[i].iov_len);
> > + packets[i].vm_pkt_iov = iov + i;
> > + }
> > +}
> > +
> > +
> > +const char *vmnet_status_map_str(vmnet_return_t status)
> > +{
> > + switch (status) {
> > + case VMNET_SUCCESS:
> > + return "success";
> > + case VMNET_FAILURE:
> > + return "general failure (possibly not enough privileges)";
> > + case VMNET_MEM_FAILURE:
> > + return "memory allocation failure";
> > + case VMNET_INVALID_ARGUMENT:
> > + return "invalid argument specified";
> > + case VMNET_SETUP_INCOMPLETE:
> > + return "interface setup is not complete";
> > + case VMNET_INVALID_ACCESS:
> > + return "invalid access, permission denied";
> > + case VMNET_PACKET_TOO_BIG:
> > + return "packet size is larger than MTU";
> > + case VMNET_BUFFER_EXHAUSTED:
> > + return "buffers exhausted in kernel";
> > + case VMNET_TOO_MANY_PACKETS:
> > + return "packet count exceeds limit";
> > +#if defined(MAC_OS_VERSION_11_0) && \
> > + MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
> > + case VMNET_SHARING_SERVICE_BUSY:
> > + return "conflict, sharing service is in use";
> > +#endif
> > + default:
> > + return "unknown vmnet error";
> > + }
> > +}
> > +
> > +
> > +int vmnet_if_create(NetClientState *nc,
> > + xpc_object_t if_desc,
> > + Error **errp)
> > +{
> > + VmnetCommonState *s = DO_UPCAST(VmnetCommonState, nc, nc);;
>
> Duplicate semicolons.
>
> > + dispatch_semaphore_t if_created_sem =
> dispatch_semaphore_create(0);
>
> if_created_sem leaks.
>
> > + __block vmnet_return_t if_status;
> > +
> > + s->if_queue = dispatch_queue_create(
> > + "org.qemu.vmnet.if_queue",
> > + DISPATCH_QUEUE_SERIAL
> > + );
> > +
> > + xpc_dictionary_set_bool(
> > + if_desc,
> > + vmnet_allocate_mac_address_key,
> > + false
> > + );
> > +#ifdef DEBUG
> > + qemu_log("vmnet.start.interface_desc:\n");
> > + xpc_dictionary_apply(if_desc,
> > + ^bool(const char *k, xpc_object_t v) {
> > + char *desc = xpc_copy_description(v);
> > + qemu_log(" %s=%s\n", k, desc);
> > + free(desc);
> > + return true;
> > + });
> > +#endif /* DEBUG */
> > +
> > + s->vmnet_if = vmnet_start_interface(
> > + if_desc,
> > + s->if_queue,
> > + ^(vmnet_return_t status, xpc_object_t interface_param) {
> > + if_status = status;
> > + if (status != VMNET_SUCCESS || !interface_param) {
> > + dispatch_semaphore_signal(if_created_sem);
> > + return;
> > + }
> > +
> > +#ifdef DEBUG
> > + qemu_log("vmnet.start.interface_param:\n");
> > + xpc_dictionary_apply(interface_param,
> > + ^bool(const char *k,
> xpc_object_t v) {
> > + char *desc =
> xpc_copy_description(v);
> > + qemu_log(" %s=%s\n", k, desc);
> > + free(desc);
> > + return true;
> > + });
> > +#endif /* DEBUG */
> > +
> > + s->mtu = xpc_dictionary_get_uint64(
> > + interface_param,
> > + vmnet_mtu_key);
> > + s->max_packet_size = xpc_dictionary_get_uint64(
> > + interface_param,
> > + vmnet_max_packet_size_key);
> > +
> > + dispatch_semaphore_signal(if_created_sem);
> > + });
> > +
> > + if (s->vmnet_if == NULL) {
> > + error_setg(errp,
> > + "unable to create interface "
> > + "with requested params");
>
> You don't need line breaks here. Breaking a string into a few would
> also
> makes it a bit hard to grep.
>
> > + return -1;
>
> s->if_queue leaks.
>
> > + }
> > +
> > + dispatch_semaphore_wait(if_created_sem, DISPATCH_TIME_FOREVER);
> > +
> > + if (if_status != VMNET_SUCCESS) {
> > + error_setg(errp,
> > + "cannot create vmnet interface: %s",
> > + vmnet_status_map_str(if_status));
> > + return -1;
> > + }
> > +
> > + s->send_bh = aio_bh_new(qemu_get_aio_context(),
> vmnet_send_bh, nc);
> > + vmnet_bufs_init(s);
> > + vmnet_set_send_bh_scheduled(s, false);
> > + vmnet_set_send_enabled(s, true);
> > + return 0;
> > +}
> > +
> > +
> > +ssize_t vmnet_receive_common(NetClientState *nc,
> > + const uint8_t *buf,
> > + size_t size)
> > +{
> > + VmnetCommonState *s = DO_UPCAST(VmnetCommonState, nc, nc);
> > + struct vmpktdesc packet;
> > + struct iovec iov;
> > + int pkt_cnt;
> > + vmnet_return_t if_status;
> > +
> > + if (size > s->max_packet_size) {
> > + warn_report("vmnet: packet is too big, %zu > %llu\n",
>
> Use PRIu64.
>
> > + packet.vm_pkt_size,
> > + s->max_packet_size);
> > + return -1;
> > + }
> > +
> > + iov.iov_base = (char *) buf;
> > + iov.iov_len = size;
> > +
> > + packet.vm_pkt_iovcnt = 1;
> > + packet.vm_flags = 0;
> > + packet.vm_pkt_size = size;
> > + packet.vm_pkt_iov = &iov;
> > + pkt_cnt = 1;
> > +
> > + if_status = vmnet_write(s->vmnet_if, &packet, &pkt_cnt);
> > + if (if_status != VMNET_SUCCESS) {
> > + error_report("vmnet: write error: %s\n",
> > + vmnet_status_map_str(if_status));
>
> Why don't return -1?
>
> > + }
> > +
> > + if (if_status == VMNET_SUCCESS && pkt_cnt) {
> > + return size;
> > + }
> > + return 0;
> > +}
> > +
> > +
> > +void vmnet_cleanup_common(NetClientState *nc)
> > +{
> > + VmnetCommonState *s = DO_UPCAST(VmnetCommonState, nc, nc);;
>
> Duplicate semicolons.
>
> > + dispatch_semaphore_t if_created_sem;
> > +
> > + qemu_purge_queued_packets(nc); > +
> vmnet_set_send_bh_scheduled(s, true);
> > + vmnet_set_send_enabled(s, false);
> > +
> > + if (s->vmnet_if == NULL) {
> > + return;
> > + }
> > +
> > + if_created_sem = dispatch_semaphore_create(0);
> > + vmnet_stop_interface(
> > + s->vmnet_if,
> > + s->if_queue,
> > + ^(vmnet_return_t status) {
> > + assert(status == VMNET_SUCCESS);
> > + dispatch_semaphore_signal(if_created_sem);
> > + });
> > + dispatch_semaphore_wait(if_created_sem, DISPATCH_TIME_FOREVER);
> > +
> > + qemu_bh_delete(s->send_bh);
> > + dispatch_release(if_created_sem);
> > + dispatch_release(s->if_queue);
> > +
> > + for (int i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
> > + g_free(s->iov_buf[i].iov_base);
> > + }
> > +}
> > diff --git a/net/vmnet-shared.c b/net/vmnet-shared.c
> > index f07afaaf21..66f66c034b 100644
> > --- a/net/vmnet-shared.c
> > +++ b/net/vmnet-shared.c
> > @@ -10,16 +10,102 @@
> >
> > #include "qemu/osdep.h"
> > #include "qapi/qapi-types-net.h"
> > +#include "qapi/error.h"
> > #include "vmnet_int.h"
> > #include "clients.h"
> > -#include "qemu/error-report.h"
> > -#include "qapi/error.h"
> >
> > #include <vmnet/vmnet.h>
> >
> > +typedef struct VmnetSharedState {
> > + VmnetCommonState cs;
> > +} VmnetSharedState;
> > +
> > +
> > +static bool validate_options(const Netdev *netdev, Error **errp)
> > +{
> > + const NetdevVmnetSharedOptions *options =
> &(netdev->u.vmnet_shared);
> > +
> > +#if !defined(MAC_OS_VERSION_11_0) || \
> > + MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_VERSION_11_0
> > + if (options->has_isolated) {
> > + error_setg(errp,
> > + "vmnet-shared.isolated feature is "
> > + "unavailable: outdated vmnet.framework API");
> > + return false;
> > + }
> > +#endif
> > +
> > + if ((options->has_start_address ||
> > + options->has_end_address ||
> > + options->has_subnet_mask) &&
> > + !(options->has_start_address &&
> > + options->has_end_address &&
> > + options->has_subnet_mask)) {
> > + error_setg(errp,
> > + "'start-address', 'end-address', 'subnet-mask' "
> > + "should be provided together"
> > + );
> > + return false;
> > + }
> > +
> > + return true;
> > +}
> > +
> > +static xpc_object_t build_if_desc(const Netdev *netdev)
> > +{
> > + const NetdevVmnetSharedOptions *options =
> &(netdev->u.vmnet_shared);
> > + xpc_object_t if_desc = xpc_dictionary_create(NULL, NULL, 0);
> > +
> > + xpc_dictionary_set_uint64(
> > + if_desc,
> > + vmnet_operation_mode_key,
> > + VMNET_SHARED_MODE
> > + );
> > +
> > + if (options->has_nat66_prefix) {
> > + xpc_dictionary_set_string(if_desc,
> > + vmnet_nat66_prefix_key,
> > + options->nat66_prefix);
> > + }
> > +
> > + if (options->has_start_address) {
> > + xpc_dictionary_set_string(if_desc,
> > + vmnet_start_address_key,
> > + options->start_address);
> > + xpc_dictionary_set_string(if_desc,
> > + vmnet_end_address_key,
> > + options->end_address);
> > + xpc_dictionary_set_string(if_desc,
> > + vmnet_subnet_mask_key,
> > + options->subnet_mask);
> > + }
> > +
> > +#if defined(MAC_OS_VERSION_11_0) && \
> > + MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
> > + xpc_dictionary_set_bool(
> > + if_desc,
> > + vmnet_enable_isolation_key,
> > + options->isolated
> > + );
> > +#endif
> > +
> > + return if_desc;
> > +}
> > +
> > +static NetClientInfo net_vmnet_shared_info = {
> > + .type = NET_CLIENT_DRIVER_VMNET_SHARED,
> > + .size = sizeof(VmnetSharedState),
> > + .receive = vmnet_receive_common,
> > + .cleanup = vmnet_cleanup_common,
> > +};
> > +
> > int net_init_vmnet_shared(const Netdev *netdev, const char *name,
> > NetClientState *peer, Error **errp)
> > {
> > - error_setg(errp, "vmnet-shared is not implemented yet");
> > - return -1;
> > + NetClientState *nc = qemu_new_net_client(&net_vmnet_shared_info,
> > + peer,
> "vmnet-shared", name);
> > + if (!validate_options(netdev, errp)) {
> > + g_assert_not_reached();
>
> g_assert_not_reached is for debugging purpose and may be dropped
> depending on the build option.
>
> > + }
> > + return vmnet_if_create(nc, build_if_desc(netdev), errp);
> > }
> > diff --git a/net/vmnet_int.h b/net/vmnet_int.h
> > index aac4d5af64..acfe3a88c0 100644
> > --- a/net/vmnet_int.h
> > +++ b/net/vmnet_int.h
> > @@ -15,11 +15,48 @@
> > #include "clients.h"
> >
> > #include <vmnet/vmnet.h>
> > +#include <dispatch/dispatch.h>
> > +
> > +/**
> > + * From vmnet.framework documentation
> > + *
> > + * Each read/write call allows up to 200 packets to be
> > + * read or written for a maximum of 256KB.
> > + *
> > + * Each packet written should be a complete
> > + * ethernet frame.
> > + *
> > + * https://developer.apple.com/documentation/vmnet
> <https://developer.apple.com/documentation/vmnet>
> > + */
> > +#define VMNET_PACKETS_LIMIT 200
> >
> > typedef struct VmnetCommonState {
> > - NetClientState nc;
> > + NetClientState nc;
> > + interface_ref vmnet_if;
> > +
> > + bool send_scheduled;
> >
> > + uint64_t mtu;
> > + uint64_t max_packet_size;
> > +
> > + struct vmpktdesc packets_buf[VMNET_PACKETS_LIMIT];
> > + struct iovec iov_buf[VMNET_PACKETS_LIMIT];
> > +
> > + dispatch_queue_t if_queue;
> > +
> > + QEMUBH *send_bh;
> > } VmnetCommonState;
> >
> > +const char *vmnet_status_map_str(vmnet_return_t status);
> > +
> > +int vmnet_if_create(NetClientState *nc,
> > + xpc_object_t if_desc,
> > + Error **errp);
> > +
> > +ssize_t vmnet_receive_common(NetClientState *nc,
> > + const uint8_t *buf,
> > + size_t size);
> > +
> > +void vmnet_cleanup_common(NetClientState *nc);
> >
> > #endif /* VMNET_INT_H */
>
>
> Other issues will be fixed and submitted later,
> thank you!
>
> Regards,
> Vladislav Yaroshchuk
Regards,
Vladislav Yaroshchuk