Pull request

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Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

# gpg: Signature made Fri 13 Dec 2019 14:32:11 GMT
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request:
  iothread: document -object iothread on man page
  virtio-blk: advertise F_WCE (F_FLUSH) if F_CONFIG_WCE is advertised

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/arm/virt.c

@@ -2149,6 +2149,7 @@ type_init(machvirt_machine_init);
 
 static void virt_machine_4_2_options(MachineClass *mc)
 {
+    compat_props_add(mc->compat_props, hw_compat_4_2, hw_compat_4_2_len);
 }
 DEFINE_VIRT_MACHINE_AS_LATEST(4, 2)
 

hw/block/virtio-blk.c

@@ -991,7 +991,9 @@ static uint64_t virtio_blk_get_features(VirtIODevice *vdev, uint64_t features,
         virtio_add_feature(&features, VIRTIO_BLK_F_SCSI);
     }
 
-    if (blk_enable_write_cache(s->blk)) {
+    if (blk_enable_write_cache(s->blk) ||
+        (s->conf.x_enable_wce_if_config_wce &&
+         virtio_has_feature(features, VIRTIO_BLK_F_CONFIG_WCE))) {
         virtio_add_feature(&features, VIRTIO_BLK_F_WCE);
     }
     if (blk_is_read_only(s->blk)) {
@@ -1270,6 +1272,8 @@ static Property virtio_blk_properties[] = {
                        conf.max_discard_sectors, BDRV_REQUEST_MAX_SECTORS),
     DEFINE_PROP_UINT32("max-write-zeroes-sectors", VirtIOBlock,
                        conf.max_write_zeroes_sectors, BDRV_REQUEST_MAX_SECTORS),
+    DEFINE_PROP_BOOL("x-enable-wce-if-config-wce", VirtIOBlock,
+                     conf.x_enable_wce_if_config_wce, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 

hw/core/machine.c

@@ -27,6 +27,11 @@
 #include "hw/pci/pci.h"
 #include "hw/mem/nvdimm.h"
 
+GlobalProperty hw_compat_4_2[] = {
+    { "virtio-blk-device", "x-enable-wce-if-config-wce", "off" },
+};
+const size_t hw_compat_4_2_len = G_N_ELEMENTS(hw_compat_4_2);
+
 GlobalProperty hw_compat_4_1[] = {
     { "virtio-pci", "x-pcie-flr-init", "off" },
 };

hw/i386/pc_piix.c

@@ -431,6 +431,7 @@ static void pc_i440fx_4_2_machine_options(MachineClass *m)
     m->alias = "pc";
     m->is_default = 1;
     pcmc->default_cpu_version = 1;
+    compat_props_add(m->compat_props, hw_compat_4_2, hw_compat_4_2_len);
 }
 
 DEFINE_I440FX_MACHINE(v4_2, "pc-i440fx-4.2", NULL,

hw/i386/pc_q35.c

@@ -354,6 +354,7 @@ static void pc_q35_4_2_machine_options(MachineClass *m)
     pc_q35_machine_options(m);
     m->alias = "q35";
     pcmc->default_cpu_version = 1;
+    compat_props_add(m->compat_props, hw_compat_4_2, hw_compat_4_2_len);
 }
 
 DEFINE_Q35_MACHINE(v4_2, "pc-q35-4.2", NULL,

hw/ppc/spapr.c

@@ -4496,7 +4496,7 @@ static const TypeInfo spapr_machine_info = {
  */
 static void spapr_machine_4_2_class_options(MachineClass *mc)
 {
-    /* Defaults for the latest behaviour inherited from the base class */
+    compat_props_add(mc->compat_props, hw_compat_4_2, hw_compat_4_2_len);
 }
 
 DEFINE_SPAPR_MACHINE(4_2, "4.2", true);

hw/s390x/s390-virtio-ccw.c

@@ -645,6 +645,7 @@ static void ccw_machine_4_2_instance_options(MachineState *machine)
 
 static void ccw_machine_4_2_class_options(MachineClass *mc)
 {
+    compat_props_add(mc->compat_props, hw_compat_4_2, hw_compat_4_2_len);
 }
 DEFINE_CCW_MACHINE(4_2, "4.2", true);
 

include/hw/boards.h

@@ -329,6 +329,9 @@ struct MachineState {
     } \
     type_init(machine_initfn##_register_types)
 
+extern GlobalProperty hw_compat_4_2[];
+extern const size_t hw_compat_4_2_len;
+
 extern GlobalProperty hw_compat_4_1[];
 extern const size_t hw_compat_4_1_len;
 

include/hw/virtio/virtio-blk.h

@@ -40,6 +40,7 @@ struct VirtIOBlkConf
     uint16_t queue_size;
     uint32_t max_discard_sectors;
     uint32_t max_write_zeroes_sectors;
+    bool x_enable_wce_if_config_wce;
 };
 
 struct VirtIOBlockDataPlane;

qemu-options.hx

@@ -4916,6 +4916,44 @@ access
 CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB
 @end example
 
+@item -object iothread,id=@var{id},poll-max-ns=@var{poll-max-ns},poll-grow=@var{poll-grow},poll-shrink=@var{poll-shrink}
+
+Creates a dedicated event loop thread that devices can be assigned to.  This is
+known as an IOThread.  By default device emulation happens in vCPU threads or
+the main event loop thread.  This can become a scalability bottleneck.
+IOThreads allow device emulation and I/O to run on other host CPUs.
+
+The @option{id} parameter is a unique ID that will be used to reference this
+IOThread from @option{-device ...,iothread=@var{id}}.  Multiple devices can be
+assigned to an IOThread.  Note that not all devices support an
+@option{iothread} parameter.
+
+The @code{query-iothreads} QMP command lists IOThreads and reports their thread
+IDs so that the user can configure host CPU pinning/affinity.
+
+IOThreads use an adaptive polling algorithm to reduce event loop latency.
+Instead of entering a blocking system call to monitor file descriptors and then
+pay the cost of being woken up when an event occurs, the polling algorithm
+spins waiting for events for a short time.  The algorithm's default parameters
+are suitable for many cases but can be adjusted based on knowledge of the
+workload and/or host device latency.
+
+The @option{poll-max-ns} parameter is the maximum number of nanoseconds to busy
+wait for events.  Polling can be disabled by setting this value to 0.
+
+The @option{poll-grow} parameter is the multiplier used to increase the polling
+time when the algorithm detects it is missing events due to not polling long
+enough.
+
+The @option{poll-shrink} parameter is the divisor used to decrease the polling
+time when the algorithm detects it is spending too long polling without
+encountering events.
+
+The polling parameters can be modified at run-time using the @code{qom-set} command (where @code{iothread1} is the IOThread's @code{id}):
+
+@example
+(qemu) qom-set /objects/iothread1 poll-max-ns 100000
+@end example
 
 @end table