Re: [PATCH v2 4/9] KVM: arm/arm64: replace vcpu->arch.pause with a vcpu request

[Marc Zyngier <marc.zyngier@arm.com>]

On 31/03/17 17:06, Andrew Jones wrote:
> This not only ensures visibility of changes to pause by using
> atomic ops, but also plugs a small race where a vcpu could get its
> pause state enabled just after its last check before entering the
> guest. With this patch, while the vcpu will still initially enter
> the guest, it will exit immediately due to the IPI sent by the vcpu
> kick issued after making the vcpu request.
> 
> We use bitops, rather than kvm_make/check_request(), because we
> don't need the barriers they provide, nor do we want the side-effect
> of kvm_check_request() clearing the request. For pause, only the
> requester should do the clearing.
> 
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
>  arch/arm/include/asm/kvm_host.h   |  5 +----
>  arch/arm/kvm/arm.c                | 45 +++++++++++++++++++++++++++------------
>  arch/arm64/include/asm/kvm_host.h |  5 +----
>  3 files changed, 33 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 31ee468ce667..52c25536d254 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -45,7 +45,7 @@
>  #define KVM_MAX_VCPUS VGIC_V2_MAX_CPUS
>  #endif
>  
> -#define KVM_REQ_VCPU_EXIT	8
> +#define KVM_REQ_PAUSE		8

Small nit: can we have a #define for this 8? KVM_REQ_ARCH_BASE, or
something along those lines?

I've otherwise started hammering this series over a number of systems,
looking good so far.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...