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Re: [Qemu-devel] [PATCH v1] spapr.c: Update qemu's maxcpus for pseries m
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH v1] spapr.c: Update qemu's maxcpus for pseries machine. |
Date: |
Fri, 1 Dec 2017 23:37:13 +1100 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Fri, Dec 01, 2017 at 04:54:09PM +0530, Seeteena Thoufeek wrote:
> Need to adjust the max cpus supported number from error message since
> it was conflicting with KVM's.
>
> Steps to Reproduce:
> 1.boot up with
> "-smp 64,maxcpus=102464,cores=8,threads=1,sockets=8"
>
> qemu-kvm: Number of SMP CPUs requested (102464) exceeds max CPUs
> supported by machine 'pseries-rhel7.4.0alt' (1024)
>
> 2. On KVM machine it shows
>
> boot up with
> "-m 6G,maxmem=300G,slots=256 -smp 64,maxcpus=1024,cores=8,threads=1
> ,sockets=128"
>
> Number of hotpluggable cpus requested (1024) exceeds the maximum cpus
> supported by KVM (240)
>
> It seemed that 1024 was useless since KVM only support 240 so far.
> Hence,we need to adjust it to an reasonable value 240.
>
> Signed-off-by: Seeteena Thoufeek <address@hidden>
This has been written without adequate thought and investigation.
First, in upstream code there's nothing wrong with having different
limits in qemu and kernel - the can both vary depending on various
factors. Secondly, the 240 limit doesn't come from the kernel
upstream - only in RHEL.
Third, it doesn't even come from the kernel in RHEL - the downstream
qemu lies about the kernel limit.
I'm in the process of fixing this correctly, I expect to have
something on Monday.
> ---
> hw/ppc/spapr.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 9efddea..c753254 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -3691,6 +3691,7 @@ static const TypeInfo spapr_machine_info = {
> if (latest) { \
> mc->alias = "pseries"; \
> mc->is_default = 1; \
> + mc->max_cpus = 240; \
> } \
> } \
> static void spapr_machine_##suffix##_instance_init(Object *obj) \
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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