[PATCH v4 2/3] spapr: nvdimm: Implement H_SCM_FLUSH hcall

From: Shivaprasad G Bhat <sbhat@linux.ibm.com>
To: david@gibson.dropbear.id.au, groug@kaod.org, qemu-ppc@nongnu.org,
	ehabkost@redhat.com, marcel.apfelbaum@gmail.com, mst@redhat.com,
	imammedo@redhat.com, xiaoguangrong.eric@gmail.com,
	peter.maydell@linaro.org, eblake@redhat.com, qemu-arm@nongnu.org,
	richard.henderson@linaro.org, pbonzini@redhat.com,
	marcel.apfelbaum@gmail.com, stefanha@redhat.com,
	haozhong.zhang@intel.com, shameerali.kolothum.thodi@huawei.com,
	kwangwoo.lee@sk.com, armbru@redhat.com
Cc: qemu-devel@nongnu.org, aneesh.kumar@linux.ibm.com,
	linux-nvdimm@lists.01.org, kvm-ppc@vger.kernel.org,
	shivaprasadbhat@gmail.com, bharata@linux.vnet.ibm.com
Subject: [PATCH v4 2/3] spapr: nvdimm: Implement H_SCM_FLUSH hcall
Date: Wed, 28 Apr 2021 23:48:50 -0400	[thread overview]
Message-ID: <161966812696.652.15987779677314301634.stgit@17be908f7c1c> (raw)
In-Reply-To: <161966810162.652.13723419108625443430.stgit@17be908f7c1c>

The patch adds support for the SCM flush hcall for the nvdimm devices.
To be available for exploitation by guest through the next patch.

The hcall expects the semantics such that the flush to return
with H_BUSY when the operation is expected to take longer time along
with a continue_token. The hcall to be called again providing the
continue_token to get the status. So, all fresh requsts are put into
a 'pending' list and flush worker is submitted to the thread pool.
The thread pool completion callbacks move the requests to 'completed'
list, which are cleaned up after reporting to guest in subsequent
hcalls to get the status.

The semantics makes it necessary to preserve the continue_tokens
and their return status across migrations. So, the completed
flush states are forwarded to the destination and the pending
ones are restarted at the destination in post_load. The necessary
nvdimm flush specific vmstate structures are added to the spapr
machine vmstate.

Signed-off-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
---
 hw/ppc/spapr.c                |    6 +
 hw/ppc/spapr_nvdimm.c         |  234 +++++++++++++++++++++++++++++++++++++++++
 include/hw/ppc/spapr.h        |   10 ++
 include/hw/ppc/spapr_nvdimm.h |   13 ++
 4 files changed, 262 insertions(+), 1 deletion(-)

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e4be00b732..80957f9188 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1607,6 +1607,8 @@ static void spapr_machine_reset(MachineState *machine)
         spapr->ov5_cas = spapr_ovec_clone(spapr->ov5);
     }
 
+    spapr_nvdimm_finish_flushes(spapr);
+
     /* DRC reset may cause a device to be unplugged. This will cause troubles
      * if this device is used by another device (eg, a running vhost backend
      * will crash QEMU if the DIMM holding the vring goes away). To avoid such
@@ -2003,6 +2005,7 @@ static const VMStateDescription vmstate_spapr = {
         &vmstate_spapr_cap_ccf_assist,
         &vmstate_spapr_cap_fwnmi,
         &vmstate_spapr_fwnmi,
+        &vmstate_spapr_nvdimm_states,
         NULL
     }
 };
@@ -2997,6 +3000,9 @@ static void spapr_machine_init(MachineState *machine)
     }
 
     qemu_cond_init(&spapr->fwnmi_machine_check_interlock_cond);
+
+    QLIST_INIT(&spapr->pending_flush_states);
+    QLIST_INIT(&spapr->completed_flush_states);
 }
 
 #define DEFAULT_KVM_TYPE "auto"
diff --git a/hw/ppc/spapr_nvdimm.c b/hw/ppc/spapr_nvdimm.c
index 8cf3fb2ffb..77eb7e1293 100644
--- a/hw/ppc/spapr_nvdimm.c
+++ b/hw/ppc/spapr_nvdimm.c
@@ -22,6 +22,7 @@
  * THE SOFTWARE.
  */
 #include "qemu/osdep.h"
+#include "qemu/cutils.h"
 #include "qapi/error.h"
 #include "hw/ppc/spapr_drc.h"
 #include "hw/ppc/spapr_nvdimm.h"
@@ -30,6 +31,7 @@
 #include "hw/ppc/fdt.h"
 #include "qemu/range.h"
 #include "hw/ppc/spapr_numa.h"
+#include "block/thread-pool.h"
 
 /*
  * The nvdimm size should be aligned to SCM block size.
@@ -371,6 +373,237 @@ static target_ulong h_scm_bind_mem(PowerPCCPU *cpu, SpaprMachineState *spapr,
     return H_SUCCESS;
 }
 
+static uint64_t flush_token;
+
+static int flush_worker_cb(void *opaque)
+{
+    int ret = H_SUCCESS;
+    SpaprNVDIMMDeviceFlushState *state = opaque;
+
+    /* flush raw backing image */
+    if (qemu_fdatasync(state->backend_fd) < 0) {
+        error_report("papr_scm: Could not sync nvdimm to backend file: %s",
+                     strerror(errno));
+        ret = H_HARDWARE;
+    }
+
+    return ret;
+}
+
+static void spapr_nvdimm_flush_completion_cb(void *opaque, int hcall_ret)
+{
+    SpaprMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
+    SpaprNVDIMMDeviceFlushState *state = opaque;
+
+    state->hcall_ret = hcall_ret;
+    QLIST_REMOVE(state, node);
+    QLIST_INSERT_HEAD(&spapr->completed_flush_states, state, node);
+}
+
+static const VMStateDescription vmstate_spapr_nvdimm_flush_state = {
+     .name = "spapr_nvdimm_flush_state",
+     .version_id = 1,
+     .minimum_version_id = 1,
+     .fields = (VMStateField[]) {
+         VMSTATE_UINT64(continue_token, SpaprNVDIMMDeviceFlushState),
+         VMSTATE_INT64(hcall_ret, SpaprNVDIMMDeviceFlushState),
+         VMSTATE_UINT32(drcidx, SpaprNVDIMMDeviceFlushState),
+         VMSTATE_END_OF_LIST()
+     },
+};
+
+static bool spapr_nvdimm_states_needed(void *opaque)
+{
+     SpaprMachineState *spapr = (SpaprMachineState *)opaque;
+
+     return (!QLIST_EMPTY(&spapr->pending_flush_states) ||
+             !QLIST_EMPTY(&spapr->completed_flush_states));
+}
+
+static int spapr_nvdimm_post_load(void *opaque, int version_id)
+{
+    SpaprMachineState *spapr = (SpaprMachineState *)opaque;
+    SpaprNVDIMMDeviceFlushState *state, *next;
+    PCDIMMDevice *dimm;
+    HostMemoryBackend *backend = NULL;
+    ThreadPool *pool = aio_get_thread_pool(qemu_get_aio_context());
+    SpaprDrc *drc;
+
+    QLIST_FOREACH_SAFE(state, &spapr->completed_flush_states, node, next) {
+        if (flush_token < state->continue_token) {
+            flush_token = state->continue_token;
+        }
+    }
+
+    QLIST_FOREACH_SAFE(state, &spapr->pending_flush_states, node, next) {
+        if (flush_token < state->continue_token) {
+            flush_token = state->continue_token;
+        }
+
+        drc = spapr_drc_by_index(state->drcidx);
+        dimm = PC_DIMM(drc->dev);
+        backend = MEMORY_BACKEND(dimm->hostmem);
+        state->backend_fd = memory_region_get_fd(&backend->mr);
+
+        thread_pool_submit_aio(pool, flush_worker_cb, state,
+                               spapr_nvdimm_flush_completion_cb, state);
+    }
+
+    return 0;
+}
+
+const VMStateDescription vmstate_spapr_nvdimm_states = {
+    .name = "spapr_nvdimm_states",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = spapr_nvdimm_states_needed,
+    .post_load = spapr_nvdimm_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_QLIST_V(completed_flush_states, SpaprMachineState, 1,
+                        vmstate_spapr_nvdimm_flush_state,
+                        SpaprNVDIMMDeviceFlushState, node),
+        VMSTATE_QLIST_V(pending_flush_states, SpaprMachineState, 1,
+                        vmstate_spapr_nvdimm_flush_state,
+                        SpaprNVDIMMDeviceFlushState, node),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
+/*
+ * Assign a token and reserve it for the new flush state.
+ */
+static SpaprNVDIMMDeviceFlushState *spapr_nvdimm_init_new_flush_state(
+                                                      SpaprMachineState *spapr)
+{
+    SpaprNVDIMMDeviceFlushState *state;
+
+    state = g_malloc0(sizeof(*state));
+
+    flush_token++;
+    /* Token zero is presumed as no job pending. Handle the overflow to zero */
+    if (flush_token == 0) {
+        flush_token++;
+    }
+    state->continue_token = flush_token;
+
+    QLIST_INSERT_HEAD(&spapr->pending_flush_states, state, node);
+
+    return state;
+}
+
+/*
+ * spapr_nvdimm_finish_flushes
+ *      Waits for all pending flush requests to complete
+ *      their execution and free the states
+ */
+void spapr_nvdimm_finish_flushes(SpaprMachineState *spapr)
+{
+    SpaprNVDIMMDeviceFlushState *state, *next;
+
+    /*
+     * Called on reset path, the main loop thread which calls
+     * the pending BHs has gotten out running in the reset path,
+     * finally reaching here. Other code path being guest
+     * h_client_architecture_support, thats early boot up.
+     */
+    while (!QLIST_EMPTY(&spapr->pending_flush_states)) {
+        aio_poll(qemu_get_aio_context(), true);
+    }
+
+    QLIST_FOREACH_SAFE(state, &spapr->completed_flush_states, node, next) {
+        QLIST_REMOVE(state, node);
+        g_free(state);
+    }
+}
+
+/*
+ * spapr_nvdimm_get_flush_status
+ *      Fetches the status of the hcall worker and returns
+ *      H_LONG_BUSY_XYZ if the worker is still running.
+ */
+static int spapr_nvdimm_get_flush_status(SpaprMachineState *spapr,
+                                         uint64_t token)
+{
+    int ret = H_LONG_BUSY_ORDER_10_MSEC;
+    SpaprNVDIMMDeviceFlushState *state, *node;
+
+    QLIST_FOREACH_SAFE(state, &spapr->pending_flush_states, node, node) {
+        if (state->continue_token == token) {
+            goto exit;
+        }
+    }
+    ret = H_P2; /* If not found in complete list too, invalid token */
+    QLIST_FOREACH_SAFE(state, &spapr->completed_flush_states, node, node) {
+        if (state->continue_token == token) {
+            ret = state->hcall_ret;
+            QLIST_REMOVE(state, node);
+            g_free(state);
+            break;
+        }
+    }
+exit:
+    return ret;
+}
+
+/*
+ * H_SCM_FLUSH
+ * Input: drc_index, continue-token
+ * Out: continue-token
+ * Return Value: H_SUCCESS, H_Parameter, H_P2, H_LONG_BUSY
+ *
+ * Given a DRC Index Flush the data to backend NVDIMM device.
+ * The hcall returns H_LONG_BUSY_XX when the flush takes longer time and
+ * the hcall needs to be issued multiple times in order to be completely
+ * serviced. The continue-token from the output to be passed in the
+ * argument list of subsequent hcalls until the hcall is completely serviced
+ * at which point H_SUCCESS or other error is returned.
+ */
+static target_ulong h_scm_flush(PowerPCCPU *cpu, SpaprMachineState *spapr,
+                                      target_ulong opcode, target_ulong *args)
+{
+    int ret;
+    uint32_t drc_index = args[0];
+    uint64_t continue_token = args[1];
+    SpaprDrc *drc = spapr_drc_by_index(drc_index);
+    PCDIMMDevice *dimm;
+    HostMemoryBackend *backend = NULL;
+    SpaprNVDIMMDeviceFlushState *state;
+    ThreadPool *pool = aio_get_thread_pool(qemu_get_aio_context());
+
+    if (!drc || !drc->dev ||
+        spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
+        return H_PARAMETER;
+    }
+
+    if (continue_token != 0) {
+        goto get_status;
+    }
+
+    dimm = PC_DIMM(drc->dev);
+    backend = MEMORY_BACKEND(dimm->hostmem);
+
+    state = spapr_nvdimm_init_new_flush_state(spapr);
+    if (!state) {
+        return H_HARDWARE;
+    }
+
+    state->drcidx = drc_index;
+    state->backend_fd = memory_region_get_fd(&backend->mr);
+
+    thread_pool_submit_aio(pool, flush_worker_cb, state,
+                           spapr_nvdimm_flush_completion_cb, state);
+
+    continue_token = state->continue_token;
+
+get_status:
+    ret = spapr_nvdimm_get_flush_status(spapr, continue_token);
+    if (H_IS_LONG_BUSY(ret)) {
+        args[0] = continue_token;
+    }
+
+    return ret;
+}
+
 static target_ulong h_scm_unbind_mem(PowerPCCPU *cpu, SpaprMachineState *spapr,
                                      target_ulong opcode, target_ulong *args)
 {
@@ -487,6 +720,7 @@ static void spapr_scm_register_types(void)
     spapr_register_hypercall(H_SCM_BIND_MEM, h_scm_bind_mem);
     spapr_register_hypercall(H_SCM_UNBIND_MEM, h_scm_unbind_mem);
     spapr_register_hypercall(H_SCM_UNBIND_ALL, h_scm_unbind_all);
+    spapr_register_hypercall(H_SCM_FLUSH, h_scm_flush);
 }
 
 type_init(spapr_scm_register_types)
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index bf7cab7a2c..478c031396 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -12,10 +12,12 @@
 #include "hw/ppc/spapr_xive.h"  /* For SpaprXive */
 #include "hw/ppc/xics.h"        /* For ICSState */
 #include "hw/ppc/spapr_tpm_proxy.h"
+#include "hw/ppc/spapr_nvdimm.h"
 
 struct SpaprVioBus;
 struct SpaprPhbState;
 struct SpaprNvram;
+struct SpaprNVDIMMDeviceFlushState;
 
 typedef struct SpaprEventLogEntry SpaprEventLogEntry;
 typedef struct SpaprEventSource SpaprEventSource;
@@ -245,6 +247,11 @@ struct SpaprMachineState {
     uint32_t numa_assoc_array[MAX_NODES + NVGPU_MAX_NUM][NUMA_ASSOC_SIZE];
 
     Error *fwnmi_migration_blocker;
+
+    /* nvdimm flush states */
+    QLIST_HEAD(, SpaprNVDIMMDeviceFlushState) pending_flush_states;
+    QLIST_HEAD(, SpaprNVDIMMDeviceFlushState) completed_flush_states;
+
 };
 
 #define H_SUCCESS         0
@@ -538,8 +545,9 @@ struct SpaprMachineState {
 #define H_SCM_BIND_MEM          0x3EC
 #define H_SCM_UNBIND_MEM        0x3F0
 #define H_SCM_UNBIND_ALL        0x3FC
+#define H_SCM_FLUSH             0x44C
 
-#define MAX_HCALL_OPCODE        H_SCM_UNBIND_ALL
+#define MAX_HCALL_OPCODE        H_SCM_FLUSH
 
 /* The hcalls above are standardized in PAPR and implemented by pHyp
  * as well.
diff --git a/include/hw/ppc/spapr_nvdimm.h b/include/hw/ppc/spapr_nvdimm.h
index 764f999f54..24d8e37b33 100644
--- a/include/hw/ppc/spapr_nvdimm.h
+++ b/include/hw/ppc/spapr_nvdimm.h
@@ -11,6 +11,7 @@
 #define HW_SPAPR_NVDIMM_H
 
 #include "hw/mem/nvdimm.h"
+#include "migration/vmstate.h"
 
 typedef struct SpaprDrc SpaprDrc;
 typedef struct SpaprMachineState SpaprMachineState;
@@ -21,5 +22,17 @@ void spapr_dt_persistent_memory(SpaprMachineState *spapr, void *fdt);
 bool spapr_nvdimm_validate(HotplugHandler *hotplug_dev, NVDIMMDevice *nvdimm,
                            uint64_t size, Error **errp);
 void spapr_add_nvdimm(DeviceState *dev, uint64_t slot);
+void spapr_nvdimm_finish_flushes(SpaprMachineState *spapr);
+
+typedef struct SpaprNVDIMMDeviceFlushState {
+    uint64_t continue_token;
+    int64_t hcall_ret;
+    int backend_fd;
+    uint32_t drcidx;
+
+    QLIST_ENTRY(SpaprNVDIMMDeviceFlushState) node;
+} SpaprNVDIMMDeviceFlushState;
+
+extern const VMStateDescription vmstate_spapr_nvdimm_states;
 
 #endif

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