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[libvirt] [PATCH] qemu: Start domain on a node without cpu affinity

Roman Bolshakov posted 1 patch 7 years, 5 months ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/libvirt tags/patchew/20180821213129.11381-1-r.bolshakov@yadro.com
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src/qemu/qemu_driver.c | 6 ++++++
src/util/virprocess.c  | 2 +-
2 files changed, 7 insertions(+), 1 deletion(-)
[libvirt] [PATCH] qemu: Start domain on a node without cpu affinity
Posted by Roman Bolshakov 7 years, 5 months ago 
libvirt affinity wrappers don't support macOS Thread Affinity API:
https://developer.apple.com/library/archive/releasenotes/Performance/RN-AffinityAPI/index.html

virProcessSetAffinity stub prevents libvirt from starting a qemu domain
on macOS:

$ virsh start vm
error: Failed to start domain vm
error: Process CPU affinity is not supported on this platform: Function not implemented

With the patch a VM can be started on macOS but some affinity-related
commands will return errors:

$ virsh vcpuinfo vm
error: Requested operation is not valid: cpu affinity is not supported

$ virsh vcpupin vm
VCPU: CPU Affinity
----------------------------------
   0: 0-7

$ virsh vcpupin vm --live --vcpu 0 --cpulist 7
error: operation failed: Virt type 'qemu' does not support vCPU pinning

$ virsh emulatorpin vm
emulator: CPU Affinity
----------------------------------
       *: 0-7

$ virsh emulatorpin vm --live --cpulist 7
error: Requested operation is not valid: cpu affinity is not supported

The patch also fixes virmacmaptest on macOS

Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 src/qemu/qemu_driver.c | 6 ++++++
 src/util/virprocess.c  | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 21e9e87ddd..2e225b1ede 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -5245,6 +5245,12 @@ qemuDomainPinEmulator(virDomainPtr dom,
     if (virDomainPinEmulatorEnsureACL(dom->conn, vm->def, flags) < 0)
         goto cleanup;
 
+    if (!qemuDomainHasVcpuPids(vm)) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       "%s", _("cpu affinity is not supported"));
+        goto cleanup;
+    }
+
     if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
         goto cleanup;
 
diff --git a/src/util/virprocess.c b/src/util/virprocess.c
index 3988f5546c..7eaafd29f2 100644
--- a/src/util/virprocess.c
+++ b/src/util/virprocess.c
@@ -598,7 +598,7 @@ int virProcessSetAffinity(pid_t pid ATTRIBUTE_UNUSED,
 {
     virReportSystemError(ENOSYS, "%s",
                          _("Process CPU affinity is not supported on this platform"));
-    return -1;
+    return 0;
 }
 
 virBitmapPtr
-- 
2.15.2 (Apple Git-101.1)

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Re: [libvirt] [PATCH] qemu: Start domain on a node without cpu affinity
Posted by Peter Krempa 7 years, 5 months ago 
On Wed, Aug 22, 2018 at 00:31:29 +0300, Roman Bolshakov wrote:
> libvirt affinity wrappers don't support macOS Thread Affinity API:
> https://developer.apple.com/library/archive/releasenotes/Performance/RN-AffinityAPI/index.html
> 
> virProcessSetAffinity stub prevents libvirt from starting a qemu domain
> on macOS:
> 
> $ virsh start vm
> error: Failed to start domain vm
> error: Process CPU affinity is not supported on this platform: Function not implemented
> 
> With the patch a VM can be started on macOS but some affinity-related
> commands will return errors:
> 
> $ virsh vcpuinfo vm
> error: Requested operation is not valid: cpu affinity is not supported
> 
> $ virsh vcpupin vm
> VCPU: CPU Affinity
> ----------------------------------
>    0: 0-7
> 
> $ virsh vcpupin vm --live --vcpu 0 --cpulist 7
> error: operation failed: Virt type 'qemu' does not support vCPU pinning
> 
> $ virsh emulatorpin vm
> emulator: CPU Affinity
> ----------------------------------
>        *: 0-7
> 
> $ virsh emulatorpin vm --live --cpulist 7
> error: Requested operation is not valid: cpu affinity is not supported
> 
> The patch also fixes virmacmaptest on macOS
> 
> Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
> ---
>  src/qemu/qemu_driver.c | 6 ++++++
>  src/util/virprocess.c  | 2 +-
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 21e9e87ddd..2e225b1ede 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -5245,6 +5245,12 @@ qemuDomainPinEmulator(virDomainPtr dom,
>      if (virDomainPinEmulatorEnsureACL(dom->conn, vm->def, flags) < 0)
>          goto cleanup;
>  
> +    if (!qemuDomainHasVcpuPids(vm)) {
> +        virReportError(VIR_ERR_OPERATION_INVALID,
> +                       "%s", _("cpu affinity is not supported"));
> +        goto cleanup;
> +    }
> +
>      if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
>          goto cleanup;
>  
> diff --git a/src/util/virprocess.c b/src/util/virprocess.c
> index 3988f5546c..7eaafd29f2 100644
> --- a/src/util/virprocess.c
> +++ b/src/util/virprocess.c
> @@ -598,7 +598,7 @@ int virProcessSetAffinity(pid_t pid ATTRIBUTE_UNUSED,
>  {
>      virReportSystemError(ENOSYS, "%s",
>                           _("Process CPU affinity is not supported on this platform"));
> -    return -1;
> +    return 0;

This is not a good idea. The caller should make sure that it does not
call this function if we need to support such a code path.

If you blindly return 0 here other callers might get confused.

Also setting an error and returning success is generally wrong.
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Re: [libvirt] [PATCH] qemu: Start domain on a node without cpu affinity
Posted by Daniel P. Berrangé 7 years, 5 months ago 
On Wed, Aug 22, 2018 at 09:48:10AM +0200, Peter Krempa wrote:
> On Wed, Aug 22, 2018 at 00:31:29 +0300, Roman Bolshakov wrote:
> > libvirt affinity wrappers don't support macOS Thread Affinity API:
> > https://developer.apple.com/library/archive/releasenotes/Performance/RN-AffinityAPI/index.html
> > 
> > virProcessSetAffinity stub prevents libvirt from starting a qemu domain
> > on macOS:
> > 
> > $ virsh start vm
> > error: Failed to start domain vm
> > error: Process CPU affinity is not supported on this platform: Function not implemented
> > 
> > With the patch a VM can be started on macOS but some affinity-related
> > commands will return errors:
> > 
> > $ virsh vcpuinfo vm
> > error: Requested operation is not valid: cpu affinity is not supported
> > 
> > $ virsh vcpupin vm
> > VCPU: CPU Affinity
> > ----------------------------------
> >    0: 0-7
> > 
> > $ virsh vcpupin vm --live --vcpu 0 --cpulist 7
> > error: operation failed: Virt type 'qemu' does not support vCPU pinning
> > 
> > $ virsh emulatorpin vm
> > emulator: CPU Affinity
> > ----------------------------------
> >        *: 0-7
> > 
> > $ virsh emulatorpin vm --live --cpulist 7
> > error: Requested operation is not valid: cpu affinity is not supported
> > 
> > The patch also fixes virmacmaptest on macOS
> > 
> > Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
> > ---
> >  src/qemu/qemu_driver.c | 6 ++++++
> >  src/util/virprocess.c  | 2 +-
> >  2 files changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> > index 21e9e87ddd..2e225b1ede 100644
> > --- a/src/qemu/qemu_driver.c
> > +++ b/src/qemu/qemu_driver.c
> > @@ -5245,6 +5245,12 @@ qemuDomainPinEmulator(virDomainPtr dom,
> >      if (virDomainPinEmulatorEnsureACL(dom->conn, vm->def, flags) < 0)
> >          goto cleanup;
> >  
> > +    if (!qemuDomainHasVcpuPids(vm)) {
> > +        virReportError(VIR_ERR_OPERATION_INVALID,
> > +                       "%s", _("cpu affinity is not supported"));
> > +        goto cleanup;
> > +    }
> > +
> >      if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
> >          goto cleanup;
> >  
> > diff --git a/src/util/virprocess.c b/src/util/virprocess.c
> > index 3988f5546c..7eaafd29f2 100644
> > --- a/src/util/virprocess.c
> > +++ b/src/util/virprocess.c
> > @@ -598,7 +598,7 @@ int virProcessSetAffinity(pid_t pid ATTRIBUTE_UNUSED,
> >  {
> >      virReportSystemError(ENOSYS, "%s",
> >                           _("Process CPU affinity is not supported on this platform"));
> > -    return -1;
> > +    return 0;
> 
> This is not a good idea. The caller should make sure that it does not
> call this function if we need to support such a code path.

Specifically I think you just need to turn qemuProcessInitCpuAffinity
into a no-op on macOS builds.

Of course if its possible to actually implement virProcessSetAffinity
on macOS that's an option too :-)

Regards,
Daniel
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