Hi Shiva,
On Mon, 30 Nov 2020 09:16:39 -0600
Shivaprasad G Bhat <sbhat@xxxxxxxxxxxxx> wrote:
> The patch adds support for async hcalls at the DRC level for the
> spapr devices. To be used by spapr-scm devices in the patch/es to follow.
>
> Signed-off-by: Shivaprasad G Bhat <sbhat@xxxxxxxxxxxxx>
> ---
The overall idea looks good but I think you should consider using
a thread pool to implement it. See below.
> hw/ppc/spapr_drc.c | 149 ++++++++++++++++++++++++++++++++++++++++++++
> include/hw/ppc/spapr_drc.h | 25 +++++++
> 2 files changed, 174 insertions(+)
>
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index 77718cde1f..4ecd04f686 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -15,6 +15,7 @@
> #include "qapi/qmp/qnull.h"
> #include "cpu.h"
> #include "qemu/cutils.h"
> +#include "qemu/guest-random.h"
> #include "hw/ppc/spapr_drc.h"
> #include "qom/object.h"
> #include "migration/vmstate.h"
> @@ -421,6 +422,148 @@ void spapr_drc_detach(SpaprDrc *drc)
> spapr_drc_release(drc);
> }
>
> +
> +/*
> + * @drc : device DRC targetting which the async hcalls to be made.
> + *
> + * All subsequent requests to run/query the status should use the
> + * unique token returned here.
> + */
> +uint64_t spapr_drc_get_new_async_hcall_token(SpaprDrc *drc)
> +{
> + Error *err = NULL;
> + uint64_t token;
> + SpaprDrcDeviceAsyncHCallState *tmp, *next, *state;
> +
> + state = g_malloc0(sizeof(*state));
> + state->pending = true;
> +
> + qemu_mutex_lock(&drc->async_hcall_states_lock);
> +retry:
> + if (qemu_guest_getrandom(&token, sizeof(token), &err) < 0) {
> + error_report_err(err);
> + g_free(state);
> + qemu_mutex_unlock(&drc->async_hcall_states_lock);
> + return 0;
> + }
> +
> + if (!token) /* Token should be non-zero */
> + goto retry;
> +
> + if (!QLIST_EMPTY(&drc->async_hcall_states)) {
> + QLIST_FOREACH_SAFE(tmp, &drc->async_hcall_states, node, next) {
> + if (tmp->continue_token == token) {
> + /* If the token already in use, get a new one */
> + goto retry;
> + }
> + }
> + }
> +
> + state->continue_token = token;
> + QLIST_INSERT_HEAD(&drc->async_hcall_states, state, node);
> +
> + qemu_mutex_unlock(&drc->async_hcall_states_lock);
> +
> + return state->continue_token;
> +}
> +
> +static void *spapr_drc_async_hcall_runner(void *opaque)
> +{
> + int response = -1;
> + SpaprDrcDeviceAsyncHCallState *state = opaque;
> +
> + /*
> + * state is freed only after this thread finishes(after pthread_join()),
> + * don't worry about it becoming NULL.
> + */
> +
> + response = state->func(state->data);
> +
> + state->hcall_ret = response;
> + state->pending = 0;
> +
> + return NULL;
> +}
> +
> +/*
> + * @drc : device DRC targetting which the async hcalls to be made.
> + * token : The continue token to be used for tracking as recived from
> + * spapr_drc_get_new_async_hcall_token
> + * @func() : the worker function which needs to be executed asynchronously
> + * @data : data to be passed to the asynchronous function. Worker is supposed
> + * to free/cleanup the data that is passed here
It'd be cleaner to pass a completion callback and have free/cleanup handled there.
> + */
> +void spapr_drc_run_async_hcall(SpaprDrc *drc, uint64_t token,
> + SpaprDrcAsyncHcallWorkerFunc *func, void *data)
> +{
> + SpaprDrcDeviceAsyncHCallState *state;
> +
> + qemu_mutex_lock(&drc->async_hcall_states_lock);
> + QLIST_FOREACH(state, &drc->async_hcall_states, node) {
> + if (state->continue_token == token) {
> + state->func = func;
> + state->data = data;
> + qemu_thread_create(&state->thread, "sPAPR Async HCALL",
> + spapr_drc_async_hcall_runner, state,
> + QEMU_THREAD_JOINABLE);
qemu_thread_create() exits on failure, it shouldn't be called on
a guest triggerable path, eg. a buggy guest could call it up to
the point that pthread_create() returns EAGAIN.
Please use a thread pool (see thread_pool_submit_aio()). This takes care
of all the thread housekeeping for you in a safe way, and it provides a
completion callback API. The implementation could then be just about
having two lists: one for pending requests (fed here) and one for
completed requests (fed by the completion callback).
> + break;
> + }
> + }
> + qemu_mutex_unlock(&drc->async_hcall_states_lock);
> +}
> +
> +/*
> + * spapr_drc_finish_async_hcalls
> + * Waits for all pending async requests to complete
> + * thier execution and free the states
> + */
> +static void spapr_drc_finish_async_hcalls(SpaprDrc *drc)
> +{
> + SpaprDrcDeviceAsyncHCallState *state, *next;
> +
> + if (QLIST_EMPTY(&drc->async_hcall_states)) {
> + return;
> + }
> +
> + qemu_mutex_lock(&drc->async_hcall_states_lock);
> + QLIST_FOREACH_SAFE(state, &drc->async_hcall_states, node, next) {
> + qemu_thread_join(&state->thread);
With a thread-pool, you'd just need to aio_poll() until the pending list
is empty and then clear the completed list.
> + QLIST_REMOVE(state, node);
> + g_free(state);
> + }
> + qemu_mutex_unlock(&drc->async_hcall_states_lock);
> +}
> +
> +/*
> + * spapr_drc_get_async_hcall_status
> + * Fetches the status of the hcall worker and returns H_BUSY
> + * if the worker is still running.
> + */
> +int spapr_drc_get_async_hcall_status(SpaprDrc *drc, uint64_t token)
> +{
> + int ret = H_PARAMETER;
> + SpaprDrcDeviceAsyncHCallState *state, *node;
> +
> + qemu_mutex_lock(&drc->async_hcall_states_lock);
> + QLIST_FOREACH_SAFE(state, &drc->async_hcall_states, node, node) {
> + if (state->continue_token == token) {
> + if (state->pending) {
> + ret = H_BUSY;
> + break;
> + } else {
> + ret = state->hcall_ret;
> + qemu_thread_join(&state->thread);
Like for qemu_thread_create(), the guest shouldn't be responsible for
thread housekeeping. Getting the hcall status should just be about
finding the token in the pending or completed lists.
> + QLIST_REMOVE(state, node);
> + g_free(state);
> + break;
> + }
> + }
> + }
> + qemu_mutex_unlock(&drc->async_hcall_states_lock);
> +
> + return ret;
> +}
> +
> void spapr_drc_reset(SpaprDrc *drc)
> {
> SpaprDrcClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> @@ -448,6 +591,7 @@ void spapr_drc_reset(SpaprDrc *drc)
> drc->ccs_offset = -1;
> drc->ccs_depth = -1;
> }
> + spapr_drc_finish_async_hcalls(drc);
> }
>
> static bool spapr_drc_unplug_requested_needed(void *opaque)
> @@ -558,6 +702,7 @@ SpaprDrc *spapr_dr_connector_new(Object *owner, const char *type,
> drc->owner = owner;
> prop_name = g_strdup_printf("dr-connector[%"PRIu32"]",
> spapr_drc_index(drc));
> +
Unrelated change.
> object_property_add_child(owner, prop_name, OBJECT(drc));
> object_unref(OBJECT(drc));
> qdev_realize(DEVICE(drc), NULL, NULL);
> @@ -577,6 +722,10 @@ static void spapr_dr_connector_instance_init(Object *obj)
> object_property_add(obj, "fdt", "struct", prop_get_fdt,
> NULL, NULL, NULL);
> drc->state = drck->empty_state;
> +
> + qemu_mutex_init(&drc->async_hcall_states_lock);
> + QLIST_INIT(&drc->async_hcall_states);
> +
Empty line not needed.
> }
>
> static void spapr_dr_connector_class_init(ObjectClass *k, void *data)
> diff --git a/include/hw/ppc/spapr_drc.h b/include/hw/ppc/spapr_drc.h
> index 165b281496..77f6e4386c 100644
> --- a/include/hw/ppc/spapr_drc.h
> +++ b/include/hw/ppc/spapr_drc.h
> @@ -18,6 +18,7 @@
> #include "sysemu/runstate.h"
> #include "hw/qdev-core.h"
> #include "qapi/error.h"
> +#include "block/thread-pool.h"
>
> #define TYPE_SPAPR_DR_CONNECTOR "spapr-dr-connector"
> #define SPAPR_DR_CONNECTOR_GET_CLASS(obj) \
> @@ -168,6 +169,21 @@ typedef enum {
> SPAPR_DRC_STATE_PHYSICAL_CONFIGURED = 8,
> } SpaprDrcState;
>
> +typedef struct SpaprDrc SpaprDrc;
> +
> +typedef int SpaprDrcAsyncHcallWorkerFunc(void *opaque);
> +typedef struct SpaprDrcDeviceAsyncHCallState {
> + uint64_t continue_token;
> + bool pending;
> +
> + int hcall_ret;
> + SpaprDrcAsyncHcallWorkerFunc *func;
> + void *data;
> +
> + QemuThread thread;
> +
> + QLIST_ENTRY(SpaprDrcDeviceAsyncHCallState) node;
> +} SpaprDrcDeviceAsyncHCallState;
> typedef struct SpaprDrc {
> /*< private >*/
> DeviceState parent;
> @@ -182,6 +198,10 @@ typedef struct SpaprDrc {
> int ccs_offset;
> int ccs_depth;
>
> + /* async hcall states */
> + QemuMutex async_hcall_states_lock;
> + QLIST_HEAD(, SpaprDrcDeviceAsyncHCallState) async_hcall_states;
> +
> /* device pointer, via link property */
> DeviceState *dev;
> bool unplug_requested;
> @@ -241,6 +261,11 @@ void spapr_drc_detach(SpaprDrc *drc);
> /* Returns true if a hot plug/unplug request is pending */
> bool spapr_drc_transient(SpaprDrc *drc);
>
> +uint64_t spapr_drc_get_new_async_hcall_token(SpaprDrc *drc);
> +void spapr_drc_run_async_hcall(SpaprDrc *drc, uint64_t token,
> + SpaprDrcAsyncHcallWorkerFunc, void *data);
> +int spapr_drc_get_async_hcall_status(SpaprDrc *drc, uint64_t token);
> +
> static inline bool spapr_drc_unplug_requested(SpaprDrc *drc)
> {
> return drc->unplug_requested;
>
>
>
