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Re: [Qemu-ppc] [PATCH v1] spapr.c: Update qemu's maxcpus for pseries mac

From: seeteena
Subject: Re: [Qemu-ppc] [PATCH v1] spapr.c: Update qemu's maxcpus for pseries machine.
Date: Mon, 4 Dec 2017 12:03:03 +0530
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0

Thanks David for the explanation.

I thought the changes been into upstream code for pseries to limit

maxcpus to 240 instead of 1024.

On 12/01/2017 06:07 PM, David Gibson wrote:
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

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)  \

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