[PULL 0/2] Block patches

[PULL 0/2] Block patches

[Stefan Hajnoczi]

The following changes since commit b0ca999a43a22b38158a222233d3f5881648bb4f:

  Update version for v4.2.0 release (2019-12-12 16:45:57 +0000)

are available in the Git repository at:

  https://github.com/stefanha/qemu.git tags/block-pull-request

for you to fetch changes up to 86d2a49b41832355ab50cf60cec0cd50680fc0e5:

  iothread: document -object iothread on man page (2019-12-13 11:24:07 +0000)

----------------------------------------------------------------
Pull request

----------------------------------------------------------------

Evgeny Yakovlev (1):
  virtio-blk: advertise F_WCE (F_FLUSH) if F_CONFIG_WCE is advertised

Stefan Hajnoczi (1):
  iothread: document -object iothread on man page

 hw/arm/virt.c                  |  1 +
 hw/block/virtio-blk.c          |  6 +++++-
 hw/core/machine.c              |  5 +++++
 hw/i386/pc_piix.c              |  1 +
 hw/i386/pc_q35.c               |  1 +
 hw/ppc/spapr.c                 |  2 +-
 hw/s390x/s390-virtio-ccw.c     |  1 +
 include/hw/boards.h            |  3 +++
 include/hw/virtio/virtio-blk.h |  1 +
 qemu-options.hx                | 38 ++++++++++++++++++++++++++++++++++
 10 files changed, 57 insertions(+), 2 deletions(-)

-- 
2.23.0

[PULL 1/2] virtio-blk: advertise F_WCE (F_FLUSH) if F_CONFIG_WCE is advertised

[Stefan Hajnoczi]

From: Evgeny Yakovlev <wrfsh@yandex-team.ru>

Virtio spec 1.1 (and earlier), 5.2.5.2 Driver Requirements: Device
Initialization:

"Devices SHOULD always offer VIRTIO_BLK_F_FLUSH, and MUST offer it if
they offer VIRTIO_BLK_F_CONFIG_WCE"

Currently F_CONFIG_WCE and F_WCE are not connected to each other.
Qemu will advertise F_CONFIG_WCE if config-wce argument is
set for virtio-blk device. And F_WCE is advertised only if
underlying block backend actually has it's caching enabled.

Fix this by advertising F_WCE if F_CONFIG_WCE is also advertised.

To preserve backwards compatibility with newer machine types make this
behaviour governed by "x-enable-wce-if-config-wce" virtio-blk-device
property and introduce hw_compat_4_2 with new property being off by
default for all machine types <= 4.2 (but don't introduce 4.3
machine type itself yet).

Signed-off-by: Evgeny Yakovlev <wrfsh@yandex-team.ru>
Message-Id: <1572978137-189218-1-git-send-email-wrfsh@yandex-team.ru>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/arm/virt.c                  | 1 +
 hw/block/virtio-blk.c          | 6 +++++-
 hw/core/machine.c              | 5 +++++
 hw/i386/pc_piix.c              | 1 +
 hw/i386/pc_q35.c               | 1 +
 hw/ppc/spapr.c                 | 2 +-
 hw/s390x/s390-virtio-ccw.c     | 1 +
 include/hw/boards.h            | 3 +++
 include/hw/virtio/virtio-blk.h | 1 +
 9 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index d4bedc2607..bf4b1cbfb8 100644
--- a/hw/arm/virt.c
+++ b/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)
 
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 4c357d2928..d62e6377c2 100644
--- a/hw/block/virtio-blk.c
+++ b/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(),
 };
 
diff --git a/hw/core/machine.c b/hw/core/machine.c
index 1689ad3bf8..023548b4f3 100644
--- a/hw/core/machine.c
+++ b/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" },
 };
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 1bd70d1abb..87aced0742 100644
--- a/hw/i386/pc_piix.c
+++ b/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,
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 385e5cffb1..2608cd0062 100644
--- a/hw/i386/pc_q35.c
+++ b/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,
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e076f6023c..2ca92f2148 100644
--- a/hw/ppc/spapr.c
+++ b/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);
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index d3edeef0ad..cb5fe4c84d 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/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);
 
diff --git a/include/hw/boards.h b/include/hw/boards.h
index de45087f34..24cbeecbae 100644
--- a/include/hw/boards.h
+++ b/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;
 
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index cddcfbebe9..9c19f5b634 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/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;
-- 
2.23.0

[PULL 2/2] iothread: document -object iothread on man page

[Stefan Hajnoczi]

Add -object iothread documentation to the man page, including references
to the query-iothread QMP command and qom-set syntax for adjusting
adaptive polling parameters at run-time.

Reported-by: Zhenyu Ye <yezhenyu2@huawei.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20191025122236.29815-1-stefanha@redhat.com
Message-Id: <20191025122236.29815-1-stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 qemu-options.hx | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/qemu-options.hx b/qemu-options.hx
index 65c9473b73..68d1592ccc 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4926,6 +4926,44 @@ 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
 
-- 
2.23.0

Re: [PULL 0/2] Block patches

[Peter Maydell]

On Fri, 13 Dec 2019 at 14:33, Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> The following changes since commit b0ca999a43a22b38158a222233d3f5881648bb4f:
>
>   Update version for v4.2.0 release (2019-12-12 16:45:57 +0000)
>
> are available in the Git repository at:
>
>   https://github.com/stefanha/qemu.git tags/block-pull-request
>
> for you to fetch changes up to 86d2a49b41832355ab50cf60cec0cd50680fc0e5:
>
>   iothread: document -object iothread on man page (2019-12-13 11:24:07 +0000)
>
> ----------------------------------------------------------------
> Pull request
>
> ----------------------------------------------------------------
>

Applied, thanks.

Please update the changelog at https://wiki.qemu.org/ChangeLog/5.0
for any user-visible changes.

-- PMM