On 16/09/13 09:32, Gleb Natapov wrote: > On Mon, Sep 16, 2013 at 09:09:27AM +0100, Marc Zyngier wrote: >> On 15/09/13 10:30, Gleb Natapov wrote: >>> On Sat, Sep 14, 2013 at 02:10:55PM +0200, Andrew Jones wrote: >>>> Drop the _ARM_ part of the name. We can then introduce a config option >>>> like this to aarch64 and other arches using the same name - allowing >>>> grep to show them all. Also update the help text to describe the option >>>> more completely. >>>> >>>> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx> >>>> --- >>>> arch/arm/include/asm/kvm_host.h | 4 ++-- >>>> arch/arm/kvm/Kconfig | 8 ++++---- >>>> 2 files changed, 6 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h >>>> index 7d22517d80711..c614d3eb176c6 100644 >>>> --- a/arch/arm/include/asm/kvm_host.h >>>> +++ b/arch/arm/include/asm/kvm_host.h >>>> @@ -25,8 +25,8 @@ >>>> #include <asm/fpstate.h> >>>> #include <kvm/arm_arch_timer.h> >>>> >>>> -#if defined(CONFIG_KVM_ARM_MAX_VCPUS) >>>> -#define KVM_MAX_VCPUS CONFIG_KVM_ARM_MAX_VCPUS >>>> +#if defined(CONFIG_KVM_MAX_VCPUS) >>>> +#define KVM_MAX_VCPUS CONFIG_KVM_MAX_VCPUS >>>> #else >>>> #define KVM_MAX_VCPUS 0 >>>> #endif >>>> diff --git a/arch/arm/kvm/Kconfig b/arch/arm/kvm/Kconfig >>>> index ebf5015508b52..de63bfccb3eb5 100644 >>>> --- a/arch/arm/kvm/Kconfig >>>> +++ b/arch/arm/kvm/Kconfig >>>> @@ -40,16 +40,16 @@ config KVM_ARM_HOST >>>> ---help--- >>>> Provides host support for ARM processors. >>>> >>>> -config KVM_ARM_MAX_VCPUS >>>> +config KVM_MAX_VCPUS >>>> int "Number maximum supported virtual CPUs per VM" >>>> depends on KVM_ARM_HOST >>>> default 4 >>>> help >>>> Static number of max supported virtual CPUs per VM. >>>> >>>> - If you choose a high number, the vcpu structures will be quite >>>> - large, so only choose a reasonable number that you expect to >>>> - actually use. >>> I do no see why on ARM vcpu structure size depends on KVM_ARM_MAX_VCPUS. >>> Can somebody point me to it. >> >> There's a number of indirections, but here you go: >> arch/arm/include/asm/kvm_host.h:#define KVM_MAX_VCPUS CONFIG_KVM_ARM_MAX_VCPUS >> >> include/kvm/arm_vgic.h:#define VGIC_MAX_CPUS KVM_MAX_VCPUS >> >> include/kvm/arm_vgic.h:#if (VGIC_MAX_CPUS > 8) >> include/kvm/arm_vgic.h: } percpu[VGIC_MAX_CPUS]; >> include/kvm/arm_vgic.h: u32 percpu[VGIC_MAX_CPUS][VGIC_NR_PRIVATE_IRQS / 4]; >> include/kvm/arm_vgic.h: u8 irq_sgi_sources[VGIC_MAX_CPUS][VGIC_NR_SGIS]; >> include/kvm/arm_vgic.h: struct vgic_bitmap irq_spi_target[VGIC_MAX_CPUS]; >> >> Basically, the GIC emulation data structures are sized on the number of VCPUs >> (as well as the number of supported interrupts). >> > But vgic is per VM though, not per cpu as far as I can see, so the > overhead is also per VM, no? Is VGIC_MAX_CPUS limit architectural or > juts an implementation detail? Indeed, the MAX_VCPU overhead is per VM. The MAX_IRQS overhead is both per-vm and per-vcpu. The GICv2 architecture has a limit of 8 CPUs - not at all an implementation detail. GICv3 remove this limitation. M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
