Re: [RFC] qemu: virtiofs can be used without NUMA nodes

[Michal Privoznik]

On 10/6/20 6:20 PM, Marc Hartmayer wrote:

...if a machine memory-backend using shared memory is configured for
the guest. This is especially important for QEMU machine types that
don't have NUMA but virtiofs support.

An example snippet:

   
 test
 2097152
 
   
 
 
   



   
   ...
 
 ...
   

and the corresponding QEMU command line:

   /usr/bin/qemu-system-s390x \
   -machine s390-ccw-virtio-5.2,memory-backend=s390.ram \
   -m 2048 \
   -object
   
memory-backend-file,id=s390.ram,mem-path=/var/lib/libvirt/qemu/ram/46-test/s390.ram,share=yes,size=2147483648
 \
   ...

Signed-off-by: Marc Hartmayer 
---
Note: There are still some TODOs left... e.g. adapt the virtiofs
documentation of libvirt.


Yep, but looks good.


---
  src/qemu/qemu_validate.c | 15 +++
  1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index a212605579d2..077a85b30802 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -3470,14 +3470,21 @@ qemuValidateDomainDeviceDefGraphics(const 
virDomainGraphicsDef *graphics,
  
  
  static int

-qemuValidateDomainDefVirtioFSSharedMemory(const virDomainDef *def)
+qemuValidateDomainDefVirtioFSSharedMemory(const virDomainDef *def,
+  virQEMUCapsPtr qemuCaps)
  {
+const char *defaultRAMId = virQEMUCapsGetMachineDefaultRAMid(qemuCaps,
+ def->virtType,
+ 
def->os.machine);
  size_t numa_nodes = virDomainNumaGetNodeCount(def->numa);
  size_t i;
  
-if (numa_nodes == 0) {

+if (numa_nodes == 0 &&
+!(defaultRAMId && def->mem.access == VIR_DOMAIN_MEMORY_ACCESS_SHARED)) 
{
+/* TODO do we need further checks here (e.g. check whether
+ * memory backend is supported by the QEMU binary)? */


I don't think we need that. memory backends can't be compiled out (well, 
unless a distro has a patch on the top of qemu which would do exactly 
that), can defaultRAMId exposed is strictly newer than memory backends.


I think this comment can be removed and the rest can be kept as is (plus 
 the docs).


Michal

Re: [RFC] qemu: virtiofs can be used without NUMA nodes

[Marc Hartmayer]

On Tue, Oct 06, 2020 at 06:20 PM +0200, Marc Hartmayer  
wrote:
> ...if a machine memory-backend using shared memory is configured for
> the guest. This is especially important for QEMU machine types that
> don't have NUMA but virtiofs support.
>
> An example snippet:
>
>   
> test
> 2097152
> 
>   
> 
> 
>   
>   
>   
>   
>   
>   ...
> 
> ...
>   
>
> and the corresponding QEMU command line:
>
>   /usr/bin/qemu-system-s390x \
>   -machine s390-ccw-virtio-5.2,memory-backend=s390.ram \
>   -m 2048 \
>   -object
>   
> memory-backend-file,id=s390.ram,mem-path=/var/lib/libvirt/qemu/ram/46-test/s390.ram,share=yes,size=2147483648
>  \
>   ...
>
> Signed-off-by: Marc Hartmayer 
> ---
> Note: There are still some TODOs left... e.g. adapt the virtiofs
> documentation of libvirt.
> ---
>  src/qemu/qemu_validate.c | 15 +++
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
> index a212605579d2..077a85b30802 100644
> --- a/src/qemu/qemu_validate.c
> +++ b/src/qemu/qemu_validate.c
> @@ -3470,14 +3470,21 @@ qemuValidateDomainDeviceDefGraphics(const 
> virDomainGraphicsDef *graphics,
>  
>  
>  static int
> -qemuValidateDomainDefVirtioFSSharedMemory(const virDomainDef *def)
> +qemuValidateDomainDefVirtioFSSharedMemory(const virDomainDef *def,
> +  virQEMUCapsPtr qemuCaps)
>  {
> +const char *defaultRAMId = virQEMUCapsGetMachineDefaultRAMid(qemuCaps,
> + 
> def->virtType,
> + 
> def->os.machine);
>  size_t numa_nodes = virDomainNumaGetNodeCount(def->numa);
>  size_t i;
>  
> -if (numa_nodes == 0) {
> +if (numa_nodes == 0 &&
> +!(defaultRAMId && def->mem.access == 
> VIR_DOMAIN_MEMORY_ACCESS_SHARED)) {
> +/* TODO do we need further checks here (e.g. check whether
> + * memory backend is supported by the QEMU binary)? */
>  virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> -   _("virtiofs requires one or more NUMA nodes"));
> +   _("virtiofs requires shared memory"));
>  return -1;
>  }
>  
> @@ -3591,7 +3598,7 @@ qemuValidateDomainDeviceDefFS(virDomainFSDefPtr fs,
> _("virtiofs does not support multidevs"));
>  return -1;
>  }
> -if (qemuValidateDomainDefVirtioFSSharedMemory(def) < 0)
> +if (qemuValidateDomainDefVirtioFSSharedMemory(def, qemuCaps) < 0)
>  return -1;
>  break;
>  
> -- 
> 2.25.4
>

Gentle ping :)

-- 
Kind regards / Beste Grüße
   Marc Hartmayer

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