On 05/02/2016 09:14 AM, Shivaprasad G Bhat wrote:
> On PPC64, the KVM_MAX_VCPUS is defined to be 1024 where as qemu has
> MAX_CPUMASK_BITS defined at 255 in include/sysemu/sysemu.h.
>
> virsh domacapabilities and virsh maxvcpus --type kvm return different
> maxvcpus values and is confusing as to know what actually works.
>
> Signed-off-by: Shivaprasad G Bhat <sb...@linux.vnet.ibm.com>
> ---
> src/qemu/qemu_driver.c | 28 ++++++++++++++++++++++++++--
> 1 file changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 3d0c7c8..d84fc47 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -1255,10 +1255,34 @@ static int qemuConnectIsAlive(virConnectPtr conn
> ATTRIBUTE_UNUSED)
>
>
> static int
> -kvmGetMaxVCPUs(void)
> +kvmGetMaxVCPUs(virConnectPtr conn)
> {
> int fd;
> int ret;
> + virArch arch = virArchFromHost();
> + virQEMUCapsPtr qemuCaps = NULL;
> + virQEMUDriverPtr driver = conn->privateData;
> +
> + const char *machine;
> +
> + if (ARCH_IS_PPC64(arch)) {
> + if (!(qemuCaps = virQEMUCapsCacheLookupByArch(driver->qemuCapsCache,
> + arch))) {
> + virReportError(VIR_ERR_INVALID_ARG,
> + _("unable to find any emulator to serve '%s' "
> + "architecture"), virArchToString(arch));
> + return -1;
> + }
> +
> + if (!(machine = virQEMUCapsGetDefaultMachine(qemuCaps))) {
> + virObjectUnref(qemuCaps);
> + return -1;
> + }
> +
> + ret = virQEMUCapsGetMachineMaxCpus(qemuCaps, machine);
> + virObjectUnref(qemuCaps);
> + return ret;
> + }
>
I don't really like this.
The MaxVCPUs API sucks: it doesn't take enough parameters to give an accurate
picture of what the max VCPUs supported for your desired config is. And that's
basically unfixable.
Hacking in a one off fix for PPC64 here doesn't seem like a good idea. If you
really want to 'fix' this I'd suggest one or more of:
- Reflect /dev/kvm maxvcpus in the capabilities XML somehow
- Extend 'virsh maxvcpus' to take os_type+virt_type+emulator+machine_type,
look up the capabilities XML, correlate that with maxvcpus output/new
capabilities XML, and give a real value for the desired config
- Change the maxvcpus API to consistently to return capabilities output, or
cap the return value to the largest reported in capabilities output, and do it
consistently for all architectures
- Cole
> if ((fd = open(KVM_DEVICE, O_RDONLY)) < 0) {
> virReportSystemError(errno, _("Unable to open %s"), KVM_DEVICE);
> @@ -1323,7 +1347,7 @@ qemuConnectGetMaxVcpus(virConnectPtr conn
> ATTRIBUTE_UNUSED, const char *type)
> return 16;
>
> if (STRCASEEQ(type, "kvm"))
> - return kvmGetMaxVCPUs();
> + return kvmGetMaxVCPUs(conn);
>
> if (STRCASEEQ(type, "kqemu"))
> return 1;
>
--
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