[PATCH v2 0/4] docs: improve -smp documentation

[PATCH v2 0/4] docs: improve -smp documentation

[Daniel P. Berrangé]

Changed in v2:

 - Fix misplaced ',' breaking build
 - Two small typo fixes

Daniel P. Berrangé (4):
  docs: fix typo s/Intel/AMD/ in CPU model notes
  qemu-options: re-arrange CPU topology options
  qemu-options: tweak to show that CPU count is optional
  qemu-options: rewrite help for -smp options

 docs/system/cpu-models-x86.rst.inc |  2 +-
 qemu-options.hx                    | 41 ++++++++++++++++++++----------
 2 files changed, 28 insertions(+), 15 deletions(-)

-- 
2.31.1

[PATCH v2 1/4] docs: fix typo s/Intel/AMD/ in CPU model notes

[Daniel P. Berrangé]

Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 docs/system/cpu-models-x86.rst.inc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/system/cpu-models-x86.rst.inc b/docs/system/cpu-models-x86.rst.inc
index f40ee03ecc..9119f5dff5 100644
--- a/docs/system/cpu-models-x86.rst.inc
+++ b/docs/system/cpu-models-x86.rst.inc
@@ -227,7 +227,7 @@ features are included if using "Host passthrough" or "Host model".
 Preferred CPU models for AMD x86 hosts
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-The following CPU models are preferred for use on Intel hosts.
+The following CPU models are preferred for use on AMD hosts.
 Administrators / applications are recommended to use the CPU model that
 matches the generation of the host CPUs in use. In a deployment with a
 mixture of host CPU models between machines, if live migration
-- 
2.31.1

[PATCH v2 2/4] qemu-options: re-arrange CPU topology options

[Daniel P. Berrangé]

The list of CPU topology options are presented in a fairly arbitrary
order currently. Re-arrange them so that they're ordered from largest to
smallest unit

Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 qemu-options.hx | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index 8965dabc83..6b72617844 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -196,17 +196,17 @@ SRST
 ERST
 
 DEF("smp", HAS_ARG, QEMU_OPTION_smp,
-    "-smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads][,dies=dies][,sockets=sockets]\n"
+    "-smp [cpus=]n[,maxcpus=cpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]\n"
     "                set the number of CPUs to 'n' [default=1]\n"
-    "                maxcpus= maximum number of total cpus, including\n"
+    "                maxcpus= maximum number of total CPUs, including\n"
     "                offline CPUs for hotplug, etc\n"
-    "                cores= number of CPU cores on one socket (for PC, it's on one die)\n"
-    "                threads= number of threads on one CPU core\n"
+    "                sockets= number of discrete sockets in the system\n"
     "                dies= number of CPU dies on one socket (for PC only)\n"
-    "                sockets= number of discrete sockets in the system\n",
+    "                cores= number of CPU cores on one socket (for PC, it's on one die)\n"
+    "                threads= number of threads on one CPU core\n",
         QEMU_ARCH_ALL)
 SRST
-``-smp [cpus=]n[,cores=cores][,threads=threads][,dies=dies][,sockets=sockets][,maxcpus=maxcpus]``
+``-smp [cpus=]n[,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
     Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs
     are supported. On Sparc32 target, Linux limits the number of usable
     CPUs to 4. For the PC target, the number of cores per die, the
-- 
2.31.1

[PATCH v2 3/4] qemu-options: tweak to show that CPU count is optional

[Daniel P. Berrangé]

The initial CPU count number is not required, if any of the topology
options are given, since it can be computed.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 qemu-options.hx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index 6b72617844..14ff35dd4e 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -196,7 +196,7 @@ SRST
 ERST
 
 DEF("smp", HAS_ARG, QEMU_OPTION_smp,
-    "-smp [cpus=]n[,maxcpus=cpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]\n"
+    "-smp [[cpus=]n][,maxcpus=cpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]\n"
     "                set the number of CPUs to 'n' [default=1]\n"
     "                maxcpus= maximum number of total CPUs, including\n"
     "                offline CPUs for hotplug, etc\n"
@@ -206,7 +206,7 @@ DEF("smp", HAS_ARG, QEMU_OPTION_smp,
     "                threads= number of threads on one CPU core\n",
         QEMU_ARCH_ALL)
 SRST
-``-smp [cpus=]n[,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
+``-smp [[cpus=]n][,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
     Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs
     are supported. On Sparc32 target, Linux limits the number of usable
     CPUs to 4. For the PC target, the number of cores per die, the
-- 
2.31.1

[PATCH v2 4/4] qemu-options: rewrite help for -smp options

[Daniel P. Berrangé]

The -smp option help is peculiarly specific about mentioning the CPU
upper limits, but these are wrong. The "PC" target has varying max
CPU counts depending on the machine type picked. Notes about guest
OS limits are inappropriate for QEMU docs. There are way too many
machine types for it to be practical to mention actual limits, and
some limits are even modified by downstream distribtions. Thus it
is better to remove the specific limits entirely.

The CPU topology reporting is also not neccessarily specific to the
PC platform and descriptions around the rules of usage are somewhat
terse. Expand this information with some examples to show effects
of defaulting.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 qemu-options.hx | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index 14ff35dd4e..214c477dcc 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -207,14 +207,27 @@ DEF("smp", HAS_ARG, QEMU_OPTION_smp,
         QEMU_ARCH_ALL)
 SRST
 ``-smp [[cpus=]n][,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
-    Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs
-    are supported. On Sparc32 target, Linux limits the number of usable
-    CPUs to 4. For the PC target, the number of cores per die, the
-    number of threads per cores, the number of dies per packages and the
-    total number of sockets can be specified. Missing values will be
-    computed. If any on the three values is given, the total number of
-    CPUs n can be omitted. maxcpus specifies the maximum number of
-    hotpluggable CPUs.
+    Simulate a SMP system with '\ ``n``\ ' CPUs initially present on
+    the machine type board. On boards supporting CPU hotplug, the optional
+    '\ ``maxcpus``\ ' parameter can be set to enable further CPUs to be
+    added at runtime. If omitted the maximum number of CPUs will be
+    set to match the initial CPU count. Both parameters are subject to
+    an upper limit that is determined by the specific machine type chosen.
+
+    To control reporting of CPU topology information, the number of sockets,
+    dies per socket, cores per die, and threads per core can be specified.
+    The sum `` sockets * cores * dies * threads `` must be equal to the
+    maximum CPU count. CPU targets may only support a subset of the topology
+    parameters. Where a CPU target does not support use of a particular
+    topology parameter, its value should be assumed to be 1 for the purpose
+    of computing the CPU maximum count.
+
+    Either the initial CPU count, or at least one of the topology parameters
+    must be specified. Values for any omitted parameters will be computed
+    from those which are given. Historically preference was given to the
+    coarsest topology parameters when computing missing values (ie sockets
+    preferred over cores, which were preferred over threads), however, this
+    behaviour is considered liable to change.
 ERST
 
 DEF("numa", HAS_ARG, QEMU_OPTION_numa,
-- 
2.31.1

Re: [PATCH v2 2/4] qemu-options: re-arrange CPU topology options

[Pankaj Gupta]

> The list of CPU topology options are presented in a fairly arbitrary
> order currently. Re-arrange them so that they're ordered from largest to
> smallest unit
>
> Reviewed-by: Andrew Jones <drjones@redhat.com>
> Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  qemu-options.hx | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 8965dabc83..6b72617844 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -196,17 +196,17 @@ SRST
>  ERST
>
>  DEF("smp", HAS_ARG, QEMU_OPTION_smp,
> -    "-smp [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads][,dies=dies][,sockets=sockets]\n"
> +    "-smp [cpus=]n[,maxcpus=cpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]\n"
>      "                set the number of CPUs to 'n' [default=1]\n"
> -    "                maxcpus= maximum number of total cpus, including\n"
> +    "                maxcpus= maximum number of total CPUs, including\n"
>      "                offline CPUs for hotplug, etc\n"
> -    "                cores= number of CPU cores on one socket (for PC, it's on one die)\n"
> -    "                threads= number of threads on one CPU core\n"
> +    "                sockets= number of discrete sockets in the system\n"
>      "                dies= number of CPU dies on one socket (for PC only)\n"
> -    "                sockets= number of discrete sockets in the system\n",
> +    "                cores= number of CPU cores on one socket (for PC, it's on one die)\n"
> +    "                threads= number of threads on one CPU core\n",
>          QEMU_ARCH_ALL)
>  SRST
> -``-smp [cpus=]n[,cores=cores][,threads=threads][,dies=dies][,sockets=sockets][,maxcpus=maxcpus]``
> +``-smp [cpus=]n[,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
>      Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs
>      are supported. On Sparc32 target, Linux limits the number of usable
>      CPUs to 4. For the PC target, the number of cores per die, the
> --

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>

Re: [PATCH v2 1/4] docs: fix typo s/Intel/AMD/ in CPU model notes

[Pankaj Gupta]

> Reviewed-by: Andrew Jones <drjones@redhat.com>
> Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  docs/system/cpu-models-x86.rst.inc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/docs/system/cpu-models-x86.rst.inc b/docs/system/cpu-models-x86.rst.inc
> index f40ee03ecc..9119f5dff5 100644
> --- a/docs/system/cpu-models-x86.rst.inc
> +++ b/docs/system/cpu-models-x86.rst.inc
> @@ -227,7 +227,7 @@ features are included if using "Host passthrough" or "Host model".
>  Preferred CPU models for AMD x86 hosts
>  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> -The following CPU models are preferred for use on Intel hosts.
> +The following CPU models are preferred for use on AMD hosts.
>  Administrators / applications are recommended to use the CPU model that
>  matches the generation of the host CPUs in use. In a deployment with a
>  mixture of host CPU models between machines, if live migration
> --

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>

Re: [PATCH v2 4/4] qemu-options: rewrite help for -smp options

[Pankaj Gupta]

> The -smp option help is peculiarly specific about mentioning the CPU
> upper limits, but these are wrong. The "PC" target has varying max
> CPU counts depending on the machine type picked. Notes about guest
> OS limits are inappropriate for QEMU docs. There are way too many
> machine types for it to be practical to mention actual limits, and
> some limits are even modified by downstream distribtions. Thus it
> is better to remove the specific limits entirely.
>
> The CPU topology reporting is also not neccessarily specific to the
> PC platform and descriptions around the rules of usage are somewhat
> terse. Expand this information with some examples to show effects
> of defaulting.
>
> Reviewed-by: Andrew Jones <drjones@redhat.com>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  qemu-options.hx | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 14ff35dd4e..214c477dcc 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -207,14 +207,27 @@ DEF("smp", HAS_ARG, QEMU_OPTION_smp,
>          QEMU_ARCH_ALL)
>  SRST
>  ``-smp [[cpus=]n][,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
> -    Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs
> -    are supported. On Sparc32 target, Linux limits the number of usable
> -    CPUs to 4. For the PC target, the number of cores per die, the
> -    number of threads per cores, the number of dies per packages and the
> -    total number of sockets can be specified. Missing values will be
> -    computed. If any on the three values is given, the total number of
> -    CPUs n can be omitted. maxcpus specifies the maximum number of
> -    hotpluggable CPUs.
> +    Simulate a SMP system with '\ ``n``\ ' CPUs initially present on
> +    the machine type board. On boards supporting CPU hotplug, the optional
> +    '\ ``maxcpus``\ ' parameter can be set to enable further CPUs to be
> +    added at runtime. If omitted the maximum number of CPUs will be
> +    set to match the initial CPU count. Both parameters are subject to
> +    an upper limit that is determined by the specific machine type chosen.
> +
> +    To control reporting of CPU topology information, the number of sockets,
> +    dies per socket, cores per die, and threads per core can be specified.
> +    The sum `` sockets * cores * dies * threads `` must be equal to the
> +    maximum CPU count. CPU targets may only support a subset of the topology
> +    parameters. Where a CPU target does not support use of a particular
> +    topology parameter, its value should be assumed to be 1 for the purpose
> +    of computing the CPU maximum count.
> +
> +    Either the initial CPU count, or at least one of the topology parameters
> +    must be specified. Values for any omitted parameters will be computed
> +    from those which are given. Historically preference was given to the
> +    coarsest topology parameters when computing missing values (ie sockets
> +    preferred over cores, which were preferred over threads), however, this
> +    behaviour is considered liable to change.
>  ERST
>
>  DEF("numa", HAS_ARG, QEMU_OPTION_numa,
> --

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>

Re: [PATCH v2 3/4] qemu-options: tweak to show that CPU count is optional

[Pankaj Gupta]

> The initial CPU count number is not required, if any of the topology
> options are given, since it can be computed.
>
> Reviewed-by: Andrew Jones <drjones@redhat.com>
> Reviewed-by: Yanan Wang <wangyanan55@huawei.com>
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  qemu-options.hx | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 6b72617844..14ff35dd4e 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -196,7 +196,7 @@ SRST
>  ERST
>
>  DEF("smp", HAS_ARG, QEMU_OPTION_smp,
> -    "-smp [cpus=]n[,maxcpus=cpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]\n"
> +    "-smp [[cpus=]n][,maxcpus=cpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]\n"
>      "                set the number of CPUs to 'n' [default=1]\n"
>      "                maxcpus= maximum number of total CPUs, including\n"
>      "                offline CPUs for hotplug, etc\n"
> @@ -206,7 +206,7 @@ DEF("smp", HAS_ARG, QEMU_OPTION_smp,
>      "                threads= number of threads on one CPU core\n",
>          QEMU_ARCH_ALL)
>  SRST
> -``-smp [cpus=]n[,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
> +``-smp [[cpus=]n][,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,cores=cores][,threads=threads]``
>      Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs
>      are supported. On Sparc32 target, Linux limits the number of usable
>      CPUs to 4. For the PC target, the number of cores per die, the
> --

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>