diff mbox series

[RFC,01/13] machine: Add mirrorvcpus=N suboption to -smp

Message ID 235c91b1b09f11c75bfc60597938c97d3ebb0861.1629118207.git.ashish.kalra@amd.com (mailing list archive)
State New, archived
Headers show
Series Add support for Mirror VM. | expand

Commit Message

Kalra, Ashish Aug. 16, 2021, 1:26 p.m. UTC 
From: Dov Murik <dovmurik@linux.vnet.ibm.com>

Add a notion of mirror vcpus to CpuTopology, which will allow to
designate a few vcpus (normally 1) for running the guest
migration handler (MH).

Example usage for starting a 4-vcpu guest, of which 1 vcpu is marked as
mirror vcpu.

    qemu-system-x86_64 -smp 4,mirrorvcpus=1 ...

Signed-off-by: Dov Murik <dovmurik@linux.vnet.ibm.com>
Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 hw/core/machine.c   | 7 +++++++
 hw/i386/pc.c        | 7 +++++++
 include/hw/boards.h | 1 +
 qapi/machine.json   | 5 ++++-
 softmmu/vl.c        | 3 +++
 5 files changed, 22 insertions(+), 1 deletion(-)

Comments

Eric Blake Aug. 16, 2021, 9:23 p.m. UTC | #1 
On Mon, Aug 16, 2021 at 01:26:45PM +0000, Ashish Kalra wrote:
> From: Dov Murik <dovmurik@linux.vnet.ibm.com>
> 
> Add a notion of mirror vcpus to CpuTopology, which will allow to
> designate a few vcpus (normally 1) for running the guest
> migration handler (MH).
> 
> Example usage for starting a 4-vcpu guest, of which 1 vcpu is marked as
> mirror vcpu.
> 
>     qemu-system-x86_64 -smp 4,mirrorvcpus=1 ...
> 
> Signed-off-by: Dov Murik <dovmurik@linux.vnet.ibm.com>
> Co-developed-by: Ashish Kalra <ashish.kalra@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---

> +++ b/qapi/machine.json
> @@ -1303,6 +1303,8 @@
>  #
>  # @maxcpus: maximum number of hotpluggable virtual CPUs in the virtual machine
>  #
> +# @mirrorvcpus: maximum number of mirror virtual CPUs in the virtual machine
> +#

Needs a '(since 6.2)' tag.

>  # Since: 6.1
>  ##
>  { 'struct': 'SMPConfiguration', 'data': {
> @@ -1311,4 +1313,5 @@
>       '*dies': 'int',
>       '*cores': 'int',
>       '*threads': 'int',
> -     '*maxcpus': 'int' } }
> +     '*maxcpus': 'int',
> +     '*mirrorvcpus': 'int' } }

Is this really the right place to be adding it?  The rest of this
struct feels like things that advertise what bare metal can do, and
therefore what we are emulating.  But bare metal can't do mirrors -
that's something that is completely in the realm of emulation only.
If I understand the cover letter, the guest shouldn't be able to
detect that mirroring exists, which is different from how the guest
DOES detect how many dies, cores, and threads are available to use.
diff mbox series

Patch

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 943974d411..059262f914 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -749,6 +749,7 @@  static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
     unsigned sockets = config->has_sockets ? config->sockets : 0;
     unsigned cores   = config->has_cores ? config->cores : 0;
     unsigned threads = config->has_threads ? config->threads : 0;
+    unsigned mirror_vcpus = config->has_mirrorvcpus ? config->mirrorvcpus : 0;
 
     if (config->has_dies && config->dies != 0 && config->dies != 1) {
         error_setg(errp, "dies not supported by this machine's CPU topology");
@@ -787,6 +788,11 @@  static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
         return;
     }
 
+    if (mirror_vcpus > ms->smp.max_cpus) {
+        error_setg(errp, "mirror vcpus must be less than max cpus");
+        return;
+    }
+
     if (sockets * cores * threads != ms->smp.max_cpus) {
         error_setg(errp, "Invalid CPU topology: "
                    "sockets (%u) * cores (%u) * threads (%u) "
@@ -800,6 +806,7 @@  static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
     ms->smp.cores = cores;
     ms->smp.threads = threads;
     ms->smp.sockets = sockets;
+    ms->smp.mirror_vcpus = mirror_vcpus;
 }
 
 static void machine_get_smp(Object *obj, Visitor *v, const char *name,
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index c2b9d62a35..3856a47390 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -719,6 +719,7 @@  static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **err
     unsigned dies    = config->has_dies ? config->dies : 1;
     unsigned cores   = config->has_cores ? config->cores : 0;
     unsigned threads = config->has_threads ? config->threads : 0;
+    unsigned mirror_vcpus = config->has_mirrorvcpus ? config->mirrorvcpus : 0;
 
     /* compute missing values, prefer sockets over cores over threads */
     if (cpus == 0 || sockets == 0) {
@@ -753,6 +754,11 @@  static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **err
         return;
     }
 
+    if (mirror_vcpus > ms->smp.max_cpus) {
+        error_setg(errp, "mirror vcpus must be less than max cpus");
+        return;
+    }
+
     if (sockets * dies * cores * threads != ms->smp.max_cpus) {
         error_setg(errp, "Invalid CPU topology deprecated: "
                    "sockets (%u) * dies (%u) * cores (%u) * threads (%u) "
@@ -767,6 +773,7 @@  static void pc_smp_parse(MachineState *ms, SMPConfiguration *config, Error **err
     ms->smp.threads = threads;
     ms->smp.sockets = sockets;
     ms->smp.dies = dies;
+    ms->smp.mirror_vcpus = mirror_vcpus;
 }
 
 static
diff --git a/include/hw/boards.h b/include/hw/boards.h
index accd6eff35..b0e599096a 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -286,6 +286,7 @@  typedef struct CpuTopology {
     unsigned int threads;
     unsigned int sockets;
     unsigned int max_cpus;
+    unsigned int mirror_vcpus;
 } CpuTopology;
 
 /**
diff --git a/qapi/machine.json b/qapi/machine.json
index c3210ee1fb..7888601715 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1303,6 +1303,8 @@ 
 #
 # @maxcpus: maximum number of hotpluggable virtual CPUs in the virtual machine
 #
+# @mirrorvcpus: maximum number of mirror virtual CPUs in the virtual machine
+#
 # Since: 6.1
 ##
 { 'struct': 'SMPConfiguration', 'data': {
@@ -1311,4 +1313,5 @@ 
      '*dies': 'int',
      '*cores': 'int',
      '*threads': 'int',
-     '*maxcpus': 'int' } }
+     '*maxcpus': 'int',
+     '*mirrorvcpus': 'int' } }
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 5ca11e7469..6261f1cfb1 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -710,6 +710,9 @@  static QemuOptsList qemu_smp_opts = {
         }, {
             .name = "maxcpus",
             .type = QEMU_OPT_NUMBER,
+        }, {
+            .name = "mirrorvcpus",
+            .type = QEMU_OPT_NUMBER,
         },
         { /*End of list */ }
     },