[PATCH] KVM: PPC: Implement extension to report number of memslots

[PATCH] KVM: PPC: Implement extension to report number of memslots

[Nikunj A Dadhania]

QEMU assumes 32 memslots if this extension is not implemented. Although,
current value of KVM_USER_MEM_SLOTS is 32, once KVM_USER_MEM_SLOTS
changes QEMU would take a wrong value.

Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
---
 arch/powerpc/kvm/powerpc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 2e51289..6fd2405 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -559,6 +559,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		else
 			r = num_online_cpus();
 		break;
+	case KVM_CAP_NR_MEMSLOTS:
+		r = KVM_USER_MEM_SLOTS;
+		break;
 	case KVM_CAP_MAX_VCPUS:
 		r = KVM_MAX_VCPUS;
 		break;
-- 
2.4.3

Re: [PATCH] KVM: PPC: Implement extension to report number of memslots

[Thomas Huth]

On 16/10/15 06:57, Nikunj A Dadhania wrote:
> QEMU assumes 32 memslots if this extension is not implemented. Although,
> current value of KVM_USER_MEM_SLOTS is 32, once KVM_USER_MEM_SLOTS
> changes QEMU would take a wrong value.
> 
> Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
> ---
>  arch/powerpc/kvm/powerpc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2e51289..6fd2405 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -559,6 +559,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  		else
>  			r = num_online_cpus();
>  		break;
> +	case KVM_CAP_NR_MEMSLOTS:
> +		r = KVM_USER_MEM_SLOTS;
> +		break;
>  	case KVM_CAP_MAX_VCPUS:
>  		r = KVM_MAX_VCPUS;
>  		break;

Yes, we'll likely need this soon! 32 slots are not enough...

Reviewed-by: Thomas Huth <thuth@redhat.com>

Re: [PATCH] KVM: PPC: Implement extension to report number of memslots

[Paul Mackerras]

On Fri, Oct 16, 2015 at 08:41:31AM +0200, Thomas Huth wrote:
> Yes, we'll likely need this soon! 32 slots are not enough...

Would anyone object if I raised the limit for PPC to 512 slots?
Would that cause problems on embedded PPC, for instance?

Paul.

Re: [PATCH] KVM: PPC: Implement extension to report number of memslots

[Scott Wood]

On Mon, 2015-10-26 at 16:15 +1100, Paul Mackerras wrote:
> On Fri, Oct 16, 2015 at 08:41:31AM +0200, Thomas Huth wrote:
> > Yes, we'll likely need this soon! 32 slots are not enough...
> 
> Would anyone object if I raised the limit for PPC to 512 slots?
> Would that cause problems on embedded PPC, for instance?

I can't think of any reason why it would cause problems.

-Scott

Re: [PATCH] KVM: PPC: Implement extension to report number of memslots

[Thomas Huth]

On 26/10/15 06:15, Paul Mackerras wrote:
> On Fri, Oct 16, 2015 at 08:41:31AM +0200, Thomas Huth wrote:
>> Yes, we'll likely need this soon! 32 slots are not enough...
> 
> Would anyone object if I raised the limit for PPC to 512 slots?

In the long run we should really make this somehow dynamically instead.
But as a first step, that should IMHO be fine. Question is whether we
immediately need 512 on PPC, too? QEMU for x86 features 256 pluggable
memory DIMM slots ("#define ACPI_MAX_RAM_SLOTS 256"), while PPC only has
32 ("#define SPAPR_MAX_RAM_SLOTS 32"). So maybe we are fine with less
memory slots on PPC, e.g. 300 or so?

 Thomas