[PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[David Hildenbrand]

E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
results in
    "virtio-pmem-pci not supported on this bus"

Reasons is, that the bus does not support hotplug and, therefore, does
not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
on such buses. The hotplug order is only relevant for virtio-pmem-pci
when the guest is already alive and the device is visible before
memory_device_plug() wired up the memory device bits.

Hotplug attempts will still fail with:
    "Error: Bus 'pcie.0' does not support hotplugging"

Hotunplug attempts will still fail with:
    "Error: Bus 'pcie.0' does not support hotplugging"

Reported-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/i386/pc.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 2128f3d6fe..c740495eb6 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1663,13 +1663,13 @@ static void pc_virtio_pmem_pci_pre_plug(HotplugHandler *hotplug_dev,
     HotplugHandler *hotplug_dev2 = qdev_get_bus_hotplug_handler(dev);
     Error *local_err = NULL;
 
-    if (!hotplug_dev2) {
+    if (!hotplug_dev2 && dev->hotplugged) {
         /*
          * Without a bus hotplug handler, we cannot control the plug/unplug
-         * order. This should never be the case on x86, however better add
-         * a safety net.
+         * order. We should never reach this point when hotplugging on x86,
+         * however, better add a safety net.
          */
-        error_setg(errp, "virtio-pmem-pci not supported on this bus.");
+        error_setg(errp, "virtio-pmem-pci hotplug not supported on this bus.");
         return;
     }
     /*
@@ -1678,7 +1678,7 @@ static void pc_virtio_pmem_pci_pre_plug(HotplugHandler *hotplug_dev,
      */
     memory_device_pre_plug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev), NULL,
                            &local_err);
-    if (!local_err) {
+    if (!local_err && hotplug_dev2) {
         hotplug_handler_pre_plug(hotplug_dev2, dev, &local_err);
     }
     error_propagate(errp, local_err);
@@ -1696,9 +1696,11 @@ static void pc_virtio_pmem_pci_plug(HotplugHandler *hotplug_dev,
      * device bits.
      */
     memory_device_plug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
-    hotplug_handler_plug(hotplug_dev2, dev, &local_err);
-    if (local_err) {
-        memory_device_unplug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
+    if (hotplug_dev2) {
+        hotplug_handler_plug(hotplug_dev2, dev, &local_err);
+        if (local_err) {
+            memory_device_unplug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
+        }
     }
     error_propagate(errp, local_err);
 }
-- 
2.25.4

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[Pankaj Gupta]

> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
> results in
>     "virtio-pmem-pci not supported on this bus"
>
> Reasons is, that the bus does not support hotplug and, therefore, does
> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
> on such buses. The hotplug order is only relevant for virtio-pmem-pci
> when the guest is already alive and the device is visible before
> memory_device_plug() wired up the memory device bits.
>
> Hotplug attempts will still fail with:
>     "Error: Bus 'pcie.0' does not support hotplugging"
>
> Hotunplug attempts will still fail with:
>     "Error: Bus 'pcie.0' does not support hotplugging"
>
> Reported-by: Vivek Goyal <vgoyal@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/i386/pc.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 2128f3d6fe..c740495eb6 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1663,13 +1663,13 @@ static void pc_virtio_pmem_pci_pre_plug(HotplugHandler *hotplug_dev,
>      HotplugHandler *hotplug_dev2 = qdev_get_bus_hotplug_handler(dev);
>      Error *local_err = NULL;
>
> -    if (!hotplug_dev2) {
> +    if (!hotplug_dev2 && dev->hotplugged) {
>          /*
>           * Without a bus hotplug handler, we cannot control the plug/unplug
> -         * order. This should never be the case on x86, however better add
> -         * a safety net.
> +         * order. We should never reach this point when hotplugging on x86,
> +         * however, better add a safety net.
>           */
> -        error_setg(errp, "virtio-pmem-pci not supported on this bus.");
> +        error_setg(errp, "virtio-pmem-pci hotplug not supported on this bus.");
>          return;
>      }
>      /*
> @@ -1678,7 +1678,7 @@ static void pc_virtio_pmem_pci_pre_plug(HotplugHandler *hotplug_dev,
>       */
>      memory_device_pre_plug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev), NULL,
>                             &local_err);
> -    if (!local_err) {
> +    if (!local_err && hotplug_dev2) {
>          hotplug_handler_pre_plug(hotplug_dev2, dev, &local_err);
>      }
>      error_propagate(errp, local_err);
> @@ -1696,9 +1696,11 @@ static void pc_virtio_pmem_pci_plug(HotplugHandler *hotplug_dev,
>       * device bits.
>       */
>      memory_device_plug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
> -    hotplug_handler_plug(hotplug_dev2, dev, &local_err);
> -    if (local_err) {
> -        memory_device_unplug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
> +    if (hotplug_dev2) {
> +        hotplug_handler_plug(hotplug_dev2, dev, &local_err);
> +        if (local_err) {
> +            memory_device_unplug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
> +        }
>      }
>      error_propagate(errp, local_err);
>  }
This looks good to me & will allow to cold-plug the virtio-pmem device
on bus if they don't support hot-plug.

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

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[Vivek Goyal]

[-- Attachment #1: Type: text/plain, Size: 1574 bytes --]

On Mon, May 25, 2020 at 10:45:11AM +0200, David Hildenbrand wrote:
> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
> results in
>     "virtio-pmem-pci not supported on this bus"
> 
> Reasons is, that the bus does not support hotplug and, therefore, does
> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
> on such buses. The hotplug order is only relevant for virtio-pmem-pci
> when the guest is already alive and the device is visible before
> memory_device_plug() wired up the memory device bits.
> 
> Hotplug attempts will still fail with:
>     "Error: Bus 'pcie.0' does not support hotplugging"
> 
> Hotunplug attempts will still fail with:
>     "Error: Bus 'pcie.0' does not support hotplugging"
> 
> Reported-by: Vivek Goyal <vgoyal@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/i386/pc.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)

Thanks for the patch David. I still seem to face a different error though.

2020-05-26T13:26:05.720617Z qemu-system-x86_64: -device virtio-pmem-pci,memdev=pmem1,id=nv1: memory devices (e.g. for memory hotplug) are not enabled, please specify the maxmem option

Following is my domain xml file.

Vivek



[-- Attachment #2: vivek-vm-definition.xml --]
[-- Type: text/xml, Size: 6679 bytes --]

<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <name>vm2-f30</name>
  <uuid>c15287f2-9e66-4867-99dc-d77ece6486c8</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://fedoraproject.org/fedora/30"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit='KiB'>67108864</memory>
  <currentMemory unit='KiB'>67108864</currentMemory>
  <vcpu placement='static'>64</vcpu>
  <os>
    <type arch='x86_64' machine='pc-q35-4.2'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <vmport state='off'/>
  </features>
  <cpu mode='host-model' check='partial'>
    <model fallback='allow'/>
  </cpu>
  <clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/vm2-f30.qcow2'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='sda' bus='sata'/>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <controller type='usb' index='0' model='qemu-xhci' ports='15'>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
    </controller>
    <controller type='sata' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pcie-root'/>
    <controller type='pci' index='1' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='1' port='0x10'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0' multifunction='on'/>
    </controller>
    <controller type='pci' index='2' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='2' port='0x11'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x1'/>
    </controller>
    <controller type='pci' index='3' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='3' port='0x12'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x2'/>
    </controller>
    <controller type='pci' index='4' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='4' port='0x13'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x3'/>
    </controller>
    <controller type='pci' index='5' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='5' port='0x14'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x4'/>
    </controller>
    <controller type='pci' index='6' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='6' port='0x15'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x5'/>
    </controller>
    <controller type='pci' index='7' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='7' port='0x16'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x6'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:51:b6:34'/>
      <source network='default'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>
    <serial type='pty'>
      <target type='isa-serial' port='0'>
        <model name='isa-serial'/>
      </target>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>
    <channel type='unix'>
      <target type='virtio' name='org.qemu.guest_agent.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <channel type='spicevmc'>
      <target type='virtio' name='com.redhat.spice.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='2'/>
    </channel>
    <input type='tablet' bus='usb'>
      <address type='usb' bus='0' port='1'/>
    </input>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='spice' autoport='yes'>
      <listen type='address'/>
      <image compression='off'/>
    </graphics>
    <sound model='ich9'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1b' function='0x0'/>
    </sound>
    <video>
      <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </video>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='2'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='3'/>
    </redirdev>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
    </memballoon>
    <rng model='virtio'>
      <backend model='random'>/dev/urandom</backend>
      <address type='pci' domain='0x0000' bus='0x06' slot='0x00' function='0x0'/>
    </rng>
  </devices>
  <qemu:commandline>
    <qemu:arg value='-fsdev'/>
    <qemu:arg value='local,id=extra1,path=/mnt/virtio-9p-dir,security_model=none'/>
    <qemu:arg value='-device'/>
    <qemu:arg value='virtio-9p-pci,fsdev=extra1,mount_tag=hostShared'/>
    <qemu:arg value='-object'/>
    <qemu:arg value='memory-backend-file,id=mem,size=64G,mem-path=/dev/shm,share=on'/>
    <qemu:arg value='-numa'/>
    <qemu:arg value='node,memdev=mem'/>
    <qemu:arg value='-chardev'/>
    <qemu:arg value='socket,id=char0,path=/tmp/vhostqemu'/>
    <qemu:arg value='-device'/>
    <qemu:arg value='vhost-user-fs-pci,id=myvirtiofs,chardev=char0,tag=myfs,cache-size=64G,queue-size=1024'/>
    <qemu:arg value='-object'/>
    <qemu:arg value='memory-backend-file,id=pmem1,mem-path=/var/lib/libvirt/images/pmem-vm2-f30.img,share=on,size=4G'/>
    <qemu:arg value='-device'/>
    <qemu:arg value='virtio-pmem-pci,memdev=pmem1,id=nv1'/>
  </qemu:commandline>
</domain>

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[David Hildenbrand]

On 26.05.20 15:28, Vivek Goyal wrote:
> On Mon, May 25, 2020 at 10:45:11AM +0200, David Hildenbrand wrote:
>> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
>> results in
>>     "virtio-pmem-pci not supported on this bus"
>>
>> Reasons is, that the bus does not support hotplug and, therefore, does
>> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
>> on such buses. The hotplug order is only relevant for virtio-pmem-pci
>> when the guest is already alive and the device is visible before
>> memory_device_plug() wired up the memory device bits.
>>
>> Hotplug attempts will still fail with:
>>     "Error: Bus 'pcie.0' does not support hotplugging"
>>
>> Hotunplug attempts will still fail with:
>>     "Error: Bus 'pcie.0' does not support hotplugging"
>>
>> Reported-by: Vivek Goyal <vgoyal@redhat.com>
>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>> Cc: Igor Mammedov <imammedo@redhat.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Richard Henderson <rth@twiddle.net>
>> Cc: Eduardo Habkost <ehabkost@redhat.com>
>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>  hw/i386/pc.c | 18 ++++++++++--------
>>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> Thanks for the patch David. I still seem to face a different error though.
> 
> 2020-05-26T13:26:05.720617Z qemu-system-x86_64: -device virtio-pmem-pci,memdev=pmem1,id=nv1: memory devices (e.g. for memory hotplug) are not enabled, please specify the maxmem option
> 
> Following is my domain xml file.
> 
> Vivek

Hi Vivek,

you have to declare the maxMemory option. Memory devices like
virtio-pmem-pci reside in RAM like a pc-dimm or a nvdimm. If your
virtio-pmem device will be 4GB, you have to add that to maxMemory.

  <memory unit='GiB'>64</memory>
  <maxMemory unit='GiB'>68</maxMemory>
  <currentMemory unit='GiB'>64</currentMemory>

(you might have to add "slots='0'" or "slots='1'" to maxMemory to make
libvirt happy)

@Pankaj, do we have a virtio-pmem doc somewhere describing how to set it up?

-- 
Thanks,

David / dhildenb

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[Vivek Goyal]

On Tue, May 26, 2020 at 03:44:10PM +0200, David Hildenbrand wrote:
> On 26.05.20 15:28, Vivek Goyal wrote:
> > On Mon, May 25, 2020 at 10:45:11AM +0200, David Hildenbrand wrote:
> >> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
> >> results in
> >>     "virtio-pmem-pci not supported on this bus"
> >>
> >> Reasons is, that the bus does not support hotplug and, therefore, does
> >> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
> >> on such buses. The hotplug order is only relevant for virtio-pmem-pci
> >> when the guest is already alive and the device is visible before
> >> memory_device_plug() wired up the memory device bits.
> >>
> >> Hotplug attempts will still fail with:
> >>     "Error: Bus 'pcie.0' does not support hotplugging"
> >>
> >> Hotunplug attempts will still fail with:
> >>     "Error: Bus 'pcie.0' does not support hotplugging"
> >>
> >> Reported-by: Vivek Goyal <vgoyal@redhat.com>
> >> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> >> Cc: Igor Mammedov <imammedo@redhat.com>
> >> Cc: Paolo Bonzini <pbonzini@redhat.com>
> >> Cc: Richard Henderson <rth@twiddle.net>
> >> Cc: Eduardo Habkost <ehabkost@redhat.com>
> >> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> >> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> >> Signed-off-by: David Hildenbrand <david@redhat.com>
> >> ---
> >>  hw/i386/pc.c | 18 ++++++++++--------
> >>  1 file changed, 10 insertions(+), 8 deletions(-)
> > 
> > Thanks for the patch David. I still seem to face a different error though.
> > 
> > 2020-05-26T13:26:05.720617Z qemu-system-x86_64: -device virtio-pmem-pci,memdev=pmem1,id=nv1: memory devices (e.g. for memory hotplug) are not enabled, please specify the maxmem option
> > 
> > Following is my domain xml file.
> > 
> > Vivek
> 
> Hi Vivek,
> 
> you have to declare the maxMemory option. Memory devices like
> virtio-pmem-pci reside in RAM like a pc-dimm or a nvdimm. If your
> virtio-pmem device will be 4GB, you have to add that to maxMemory.
> 
>   <memory unit='GiB'>64</memory>
>   <maxMemory unit='GiB'>68</maxMemory>
>   <currentMemory unit='GiB'>64</currentMemory>
> 
> (you might have to add "slots='0'" or "slots='1'" to maxMemory to make
> libvirt happy)

Ok, tried that.

<maxMemory slots='1' unit='KiB'>134217728</maxMemory>

And now it complains about.

error: unsupported configuration: At least one numa node has to be configured when enabling memory hotplug

So ultimately it seems to be wanting me to somehow enable memory hotplug
to be able to use virtio-pmem?

Thanks
Vivek

> 
> @Pankaj, do we have a virtio-pmem doc somewhere describing how to set it up?
> 
> -- 
> Thanks,
> 
> David / dhildenb

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[David Hildenbrand]

On 26.05.20 16:22, Vivek Goyal wrote:
> On Tue, May 26, 2020 at 03:44:10PM +0200, David Hildenbrand wrote:
>> On 26.05.20 15:28, Vivek Goyal wrote:
>>> On Mon, May 25, 2020 at 10:45:11AM +0200, David Hildenbrand wrote:
>>>> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
>>>> results in
>>>>     "virtio-pmem-pci not supported on this bus"
>>>>
>>>> Reasons is, that the bus does not support hotplug and, therefore, does
>>>> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
>>>> on such buses. The hotplug order is only relevant for virtio-pmem-pci
>>>> when the guest is already alive and the device is visible before
>>>> memory_device_plug() wired up the memory device bits.
>>>>
>>>> Hotplug attempts will still fail with:
>>>>     "Error: Bus 'pcie.0' does not support hotplugging"
>>>>
>>>> Hotunplug attempts will still fail with:
>>>>     "Error: Bus 'pcie.0' does not support hotplugging"
>>>>
>>>> Reported-by: Vivek Goyal <vgoyal@redhat.com>
>>>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>>>> Cc: Igor Mammedov <imammedo@redhat.com>
>>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>>>> Cc: Richard Henderson <rth@twiddle.net>
>>>> Cc: Eduardo Habkost <ehabkost@redhat.com>
>>>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>>>> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
>>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>>> ---
>>>>  hw/i386/pc.c | 18 ++++++++++--------
>>>>  1 file changed, 10 insertions(+), 8 deletions(-)
>>>
>>> Thanks for the patch David. I still seem to face a different error though.
>>>
>>> 2020-05-26T13:26:05.720617Z qemu-system-x86_64: -device virtio-pmem-pci,memdev=pmem1,id=nv1: memory devices (e.g. for memory hotplug) are not enabled, please specify the maxmem option
>>>
>>> Following is my domain xml file.
>>>
>>> Vivek
>>
>> Hi Vivek,
>>
>> you have to declare the maxMemory option. Memory devices like
>> virtio-pmem-pci reside in RAM like a pc-dimm or a nvdimm. If your
>> virtio-pmem device will be 4GB, you have to add that to maxMemory.
>>
>>   <memory unit='GiB'>64</memory>
>>   <maxMemory unit='GiB'>68</maxMemory>
>>   <currentMemory unit='GiB'>64</currentMemory>
>>
>> (you might have to add "slots='0'" or "slots='1'" to maxMemory to make
>> libvirt happy)
> 
> Ok, tried that.
> 
> <maxMemory slots='1' unit='KiB'>134217728</maxMemory>
> 
> And now it complains about.
> 
> error: unsupported configuration: At least one numa node has to be configured when enabling memory hotplug
> 
> So ultimately it seems to be wanting me to somehow enable memory hotplug
> to be able to use virtio-pmem?

That's a libvirt error message. Maybe I am confused how libvirt maps
these parameters to QEMU ...

NVDIMMs under libvirt seem to be easy:

https://www.redhat.com/archives/libvir-list/2016-August/msg00055.html

Maybe the issue is that virtio-pmem has not been properly integrated
into libvirt yet:

https://www.redhat.com/archives/libvir-list/2019-August/msg00007.html

And you attempts to force virtio-pmem in via qemu args does not work
properly.

Maybe maxMemory in libvirt does not directly map to the QEMU variant to
define the maximum physical address space reserved also for any memory
devices (DIMMs, NVDIMMs, virtio-pmem, ...). Any libvirt experts that can
help?

@Pankaj, did you ever get it to run with libvirt?

> 
> Thanks
> Vivek


-- 
Thanks,

David / dhildenb

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[Daniel P. Berrangé]

On Tue, May 26, 2020 at 04:43:35PM +0200, David Hildenbrand wrote:
> On 26.05.20 16:22, Vivek Goyal wrote:
> > On Tue, May 26, 2020 at 03:44:10PM +0200, David Hildenbrand wrote:
> >> On 26.05.20 15:28, Vivek Goyal wrote:
> >>> On Mon, May 25, 2020 at 10:45:11AM +0200, David Hildenbrand wrote:
> >>>> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
> >>>> results in
> >>>>     "virtio-pmem-pci not supported on this bus"
> >>>>
> >>>> Reasons is, that the bus does not support hotplug and, therefore, does
> >>>> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
> >>>> on such buses. The hotplug order is only relevant for virtio-pmem-pci
> >>>> when the guest is already alive and the device is visible before
> >>>> memory_device_plug() wired up the memory device bits.
> >>>>
> >>>> Hotplug attempts will still fail with:
> >>>>     "Error: Bus 'pcie.0' does not support hotplugging"
> >>>>
> >>>> Hotunplug attempts will still fail with:
> >>>>     "Error: Bus 'pcie.0' does not support hotplugging"
> >>>>
> >>>> Reported-by: Vivek Goyal <vgoyal@redhat.com>
> >>>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> >>>> Cc: Igor Mammedov <imammedo@redhat.com>
> >>>> Cc: Paolo Bonzini <pbonzini@redhat.com>
> >>>> Cc: Richard Henderson <rth@twiddle.net>
> >>>> Cc: Eduardo Habkost <ehabkost@redhat.com>
> >>>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> >>>> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> >>>> Signed-off-by: David Hildenbrand <david@redhat.com>
> >>>> ---
> >>>>  hw/i386/pc.c | 18 ++++++++++--------
> >>>>  1 file changed, 10 insertions(+), 8 deletions(-)
> >>>
> >>> Thanks for the patch David. I still seem to face a different error though.
> >>>
> >>> 2020-05-26T13:26:05.720617Z qemu-system-x86_64: -device virtio-pmem-pci,memdev=pmem1,id=nv1: memory devices (e.g. for memory hotplug) are not enabled, please specify the maxmem option
> >>>
> >>> Following is my domain xml file.
> >>>
> >>> Vivek
> >>
> >> Hi Vivek,
> >>
> >> you have to declare the maxMemory option. Memory devices like
> >> virtio-pmem-pci reside in RAM like a pc-dimm or a nvdimm. If your
> >> virtio-pmem device will be 4GB, you have to add that to maxMemory.
> >>
> >>   <memory unit='GiB'>64</memory>
> >>   <maxMemory unit='GiB'>68</maxMemory>
> >>   <currentMemory unit='GiB'>64</currentMemory>
> >>
> >> (you might have to add "slots='0'" or "slots='1'" to maxMemory to make
> >> libvirt happy)
> > 
> > Ok, tried that.
> > 
> > <maxMemory slots='1' unit='KiB'>134217728</maxMemory>
> > 
> > And now it complains about.
> > 
> > error: unsupported configuration: At least one numa node has to be configured when enabling memory hotplug
> > 
> > So ultimately it seems to be wanting me to somehow enable memory hotplug
> > to be able to use virtio-pmem?
> 
> That's a libvirt error message. Maybe I am confused how libvirt maps
> these parameters to QEMU ...
> 
> NVDIMMs under libvirt seem to be easy:
> 
> https://www.redhat.com/archives/libvir-list/2016-August/msg00055.html
> 
> Maybe the issue is that virtio-pmem has not been properly integrated
> into libvirt yet:
> 
> https://www.redhat.com/archives/libvir-list/2019-August/msg00007.html

While libvirt has generic pmem support, it doesn't have virtio-pmem:

https://libvirt.org/formatdomain.html#elementsMemory

eg

  <memory model='nvdimm' access='shared'>
    <uuid>
    <source>
      <path>/dev/dax0.0</path>
      <alignsize unit='KiB'>2048</alignsize>
      <pmem/>
    </source>
    <target>
      <size unit='KiB'>524288</size>
      <node>1</node>
      <label>
        <size unit='KiB'>128</size>
      </label>
    </target>
  </memory>

> Maybe maxMemory in libvirt does not directly map to the QEMU variant to
> define the maximum physical address space reserved also for any memory
> devices (DIMMs, NVDIMMs, virtio-pmem, ...). Any libvirt experts that can
> help?

<maxMemory> reflects the upper limit on what you can hot-plug at
runtime:

   https://libvirt.org/formatdomain.html#elementsMemoryAllocation


Regards,
Daniel
-- 
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Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[Pankaj Gupta]

Hi David, Vivek,
s
> >> Hi Vivek,
> >>
> >> you have to declare the maxMemory option. Memory devices like
> >> virtio-pmem-pci reside in RAM like a pc-dimm or a nvdimm. If your
> >> virtio-pmem device will be 4GB, you have to add that to maxMemory.
> >>
> >>   <memory unit='GiB'>64</memory>
> >>   <maxMemory unit='GiB'>68</maxMemory>
> >>   <currentMemory unit='GiB'>64</currentMemory>
> >>
> >> (you might have to add "slots='0'" or "slots='1'" to maxMemory to make
> >> libvirt happy)
> >
> > Ok, tried that.
> >
> > <maxMemory slots='1' unit='KiB'>134217728</maxMemory>
> >
> > And now it complains about.
> >
> > error: unsupported configuration: At least one numa node has to be configured when enabling memory hotplug
> >
> > So ultimately it seems to be wanting me to somehow enable memory hotplug
> > to be able to use virtio-pmem?
>
> That's a libvirt error message. Maybe I am confused how libvirt maps
> these parameters to QEMU ...
>
> NVDIMMs under libvirt seem to be easy:
>
> https://www.redhat.com/archives/libvir-list/2016-August/msg00055.html
>
> Maybe the issue is that virtio-pmem has not been properly integrated
> into libvirt yet:
>
> https://www.redhat.com/archives/libvir-list/2019-August/msg00007.html
>
> And you attempts to force virtio-pmem in via qemu args does not work
> properly.
>
> Maybe maxMemory in libvirt does not directly map to the QEMU variant to
> define the maximum physical address space reserved also for any memory
> devices (DIMMs, NVDIMMs, virtio-pmem, ...). Any libvirt experts that can
> help?
>
> @Pankaj, did you ever get it to run with libvirt?

I did not run virtio-pmem with libvirt. That requires work at libvirt side.
Created [1] document to run from Qemu command line.

[1] https://github.com/qemu/qemu/blob/master/docs/virtio-pmem.rst

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[Michael S. Tsirkin]

On Mon, May 25, 2020 at 10:45:11AM +0200, David Hildenbrand wrote:
> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
> results in
>     "virtio-pmem-pci not supported on this bus"
> 
> Reasons is, that the bus does not support hotplug and, therefore, does
> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
> on such buses. The hotplug order is only relevant for virtio-pmem-pci
> when the guest is already alive and the device is visible before
> memory_device_plug() wired up the memory device bits.
> 
> Hotplug attempts will still fail with:
>     "Error: Bus 'pcie.0' does not support hotplugging"
> 
> Hotunplug attempts will still fail with:
>     "Error: Bus 'pcie.0' does not support hotplugging"
> 
> Reported-by: Vivek Goyal <vgoyal@redhat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

I assume you are still debugging Vivek's issues, right?
Let me know when you feel it's time to merge this ...

> ---
>  hw/i386/pc.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 2128f3d6fe..c740495eb6 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1663,13 +1663,13 @@ static void pc_virtio_pmem_pci_pre_plug(HotplugHandler *hotplug_dev,
>      HotplugHandler *hotplug_dev2 = qdev_get_bus_hotplug_handler(dev);
>      Error *local_err = NULL;
>  
> -    if (!hotplug_dev2) {
> +    if (!hotplug_dev2 && dev->hotplugged) {
>          /*
>           * Without a bus hotplug handler, we cannot control the plug/unplug
> -         * order. This should never be the case on x86, however better add
> -         * a safety net.
> +         * order. We should never reach this point when hotplugging on x86,
> +         * however, better add a safety net.
>           */
> -        error_setg(errp, "virtio-pmem-pci not supported on this bus.");
> +        error_setg(errp, "virtio-pmem-pci hotplug not supported on this bus.");
>          return;
>      }
>      /*
> @@ -1678,7 +1678,7 @@ static void pc_virtio_pmem_pci_pre_plug(HotplugHandler *hotplug_dev,
>       */
>      memory_device_pre_plug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev), NULL,
>                             &local_err);
> -    if (!local_err) {
> +    if (!local_err && hotplug_dev2) {
>          hotplug_handler_pre_plug(hotplug_dev2, dev, &local_err);
>      }
>      error_propagate(errp, local_err);
> @@ -1696,9 +1696,11 @@ static void pc_virtio_pmem_pci_plug(HotplugHandler *hotplug_dev,
>       * device bits.
>       */
>      memory_device_plug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
> -    hotplug_handler_plug(hotplug_dev2, dev, &local_err);
> -    if (local_err) {
> -        memory_device_unplug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
> +    if (hotplug_dev2) {
> +        hotplug_handler_plug(hotplug_dev2, dev, &local_err);
> +        if (local_err) {
> +            memory_device_unplug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev));
> +        }
>      }
>      error_propagate(errp, local_err);
>  }
> -- 
> 2.25.4

Re: [PATCH v1] pc: Support coldplugging of virtio-pmem-pci devices on all buses

[David Hildenbrand]

On 09.06.20 17:47, Michael S. Tsirkin wrote:
> On Mon, May 25, 2020 at 10:45:11AM +0200, David Hildenbrand wrote:
>> E.g., with "pc-q35-4.2", trying to coldplug a virtio-pmem-pci devices
>> results in
>>     "virtio-pmem-pci not supported on this bus"
>>
>> Reasons is, that the bus does not support hotplug and, therefore, does
>> not have a hotplug handler. Let's allow coldplugging virtio-pmem devices
>> on such buses. The hotplug order is only relevant for virtio-pmem-pci
>> when the guest is already alive and the device is visible before
>> memory_device_plug() wired up the memory device bits.
>>
>> Hotplug attempts will still fail with:
>>     "Error: Bus 'pcie.0' does not support hotplugging"
>>
>> Hotunplug attempts will still fail with:
>>     "Error: Bus 'pcie.0' does not support hotplugging"
>>
>> Reported-by: Vivek Goyal <vgoyal@redhat.com>
>> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>> Cc: Igor Mammedov <imammedo@redhat.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Richard Henderson <rth@twiddle.net>
>> Cc: Eduardo Habkost <ehabkost@redhat.com>
>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>> Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> I assume you are still debugging Vivek's issues, right?
> Let me know when you feel it's time to merge this ...

The remain issue is lack of libvirt support. This is good to be merged
from my point of view.

Thanks!


-- 
Thanks,

David / dhildenb