[PATCH] arm64: KVM: Increase max VCPUs per-Guest to 8

[Andrew Jones]

On Fri, Sep 13, 2013 at 01:46:59PM +0100, Marc Zyngier wrote:
> On 11/09/13 14:02, Anup Patel wrote:
> > Current max VCPUs per-Guest is set to 4 which is preventing
> > us from creating a Guest (or VM) with 8 VCPUs on Host (e.g.
> > X-Gene Storm SOC) with 8 Host CPUs.
> > 
> > The correct value of max VCPUs per-Guest should be same as
> > the max CPUs supported by GICv2 which is 8 hence this patch
> > increases KVM_MAX_VCPUS to 8.
> 
> If anything, please make it configurable just like we have on 32bit. No
> reason to impose the extra overhead on everyone.

What type of overhead are we talking about? Memory, right? as
kvm_for_each_vcpu is almost always used when iterating. But Anup says in
his v2 of this patch "can make things slower". If it's memory, then is so
much consumed by each vcpu that we shouldn't always set KVM_MAX_VCPUS
to at least the highest number that current hardware supports? Particularly
for aarch64 I think we should always be considering multi-platform with the
kernel configs.

drew

> 
> Thanks,
> 
> 	M.
> 
> > Signed-off-by: Anup Patel <anup.patel at linaro.org>
> > Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar at linaro.org>
> > ---
> >  arch/arm64/include/asm/kvm_host.h |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index 0859a4d..60ef29e 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -26,7 +26,7 @@
> >  #include <asm/kvm_asm.h>
> >  #include <asm/kvm_mmio.h>
> >  
> > -#define KVM_MAX_VCPUS 4
> > +#define KVM_MAX_VCPUS 8
> >  #define KVM_USER_MEM_SLOTS 32
> >  #define KVM_PRIVATE_MEM_SLOTS 4
> >  #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
> > 
> 
> 
> -- 
> Jazz is not dead. It just smells funny...
> 
> 
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