Re: [PATCH 0/3] KVM: PPC: Book3S HV: XIVE: assorted fixes on vCPU and RAM limits

Cédric Le Goater
2019-05-23T06:06:53Z

On 5/23/19 1:30 AM, David Gibson wrote:
> On Mon, May 20, 2019 at 09:15:11AM +0200, Cédric Le Goater wrote:
>> Hello,
>>
>> Here are a couple of fixes for issues in the XIVE KVM device when
>> testing the limits : RAM size and number of vCPUS.

This summary is wrong. RAM size was fixed in QEMU.

> How serious are the problems these patches fix? I'm wondering if I
> need to make a backport for RHEL8.1.

Patch 1 is a cleanup patch. It does not fix any critical issues.

Patch 2 fixes CPU hotplug. The test on the EQ flag is at the wrong
place :/ This is important I think.

Patch 3 fixes the maximum number of vCPUS supported. This one is
less important maybe, unless we want to run a guest with 1024 vCPUs.
Which is quite slow to run on most P9 systems.

QEMU emits a warning :

warning: Number of SMP cpus requested (1024) exceeds the recommended cpus supported by KVM (120)

May be we should refuse to run QEMU when that number is above a
certain threshold ?

C.

>>
>> Based on 5.2-rc1.
>>
>> Available on GitHub:
>>
>> https://github.com/legoater/linux/commits/xive-5.2
>>
>> Thanks,
>>
>> C.
>>
>> Cédric Le Goater (3):
>> KVM: PPC: Book3S HV: XIVE: clear file mapping when device is released
>> KVM: PPC: Book3S HV: XIVE: do not test the EQ flag validity when
>> reseting
>> KVM: PPC: Book3S HV: XIVE: fix the enforced limit on the vCPU
>> identifier
>>
>> arch/powerpc/kvm/book3s_xive_native.c | 46 ++++++++++++++++-----------
>> 1 file changed, 27 insertions(+), 19 deletions(-)
>>
>