Messages in this thread | | | Subject | Re: [PATCH] KVM: arm/arm64: vgic: Use a single IO device per redistributor | From | Zenghui Yu <> | Date | Tue, 27 Aug 2019 15:49:29 +0800 |
| |
Hi Eric,
Thanks for this patch!
On 2019/8/24 1:52, Auger Eric wrote: > Hi Zenghui, Marc, > > On 8/23/19 7:33 PM, Eric Auger wrote: >> At the moment we use 2 IO devices per GICv3 redistributor: one ^^^ >> one for the RD_base frame and one for the SGI_base frame. ^^^ >> >> Instead we can use a single IO device per redistributor (the 2 >> frames are contiguous). This saves slots on the KVM_MMIO_BUS >> which is currently limited to NR_IOBUS_DEVS (1000). >> >> This change allows to instantiate up to 512 redistributors and may >> speed the guest boot with a large number of VCPUs. >> >> Signed-off-by: Eric Auger <eric.auger@redhat.com> > > I tested this patch with below kernel and QEMU branches: > kernel: https://github.com/eauger/linux/tree/256fix-v1 > (Marc's patch + this patch) > https://github.com/eauger/qemu/tree/v4.1.0-256fix-rfc1-rc0 > (header update + kvm_arm_gic_set_irq modification)
I also tested these three changes on HiSi D05 (with 64 pcpus), and yes, I can get a 512U guest to boot properly now.
Tested-by: Zenghui Yu <yuzenghui@huawei.com>
> On a machine with 224 pcpus, I was able to boot a 512 vcpu guest. > > As expected, qemu outputs warnings: > > qemu-system-aarch64: warning: Number of SMP cpus requested (512) exceeds > the recommended cpus supported by KVM (224) > qemu-system-aarch64: warning: Number of hotpluggable cpus requested > (512) exceeds the recommended cpus supported by KVM (224) > > on the guest: getconf _NPROCESSORS_ONLN returns 512 > > Then I have no clue about what can be expected of such overcommit config > and I have not further exercised the guest at the moment. But at least > it seems to boot properly. I also tested without overcommit and it seems > to behave as before (boot, migration). > > I still need to look at the migration of > 256vcpu guest at qemu level.
Let us know if further tests are needed.
Thanks, zenghui
| |