Re: [PATCH v2 3/9] KVM: arm/arm64: prepare to use vcpu requests

[Christoffer Dall <cdall@linaro.org>]

On Fri, Mar 31, 2017 at 06:06:52PM +0200, Andrew Jones wrote:
> Make sure we don't leave vcpu requests we don't intend to
> handle later set in the request bitmap. If we don't clear
> them, then kvm_request_pending() may return true when we
> don't want it to.
> 
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> Acked-by: Christoffer Dall <cdall@linaro.org>
> ---
>  arch/arm/kvm/handle_exit.c   | 1 +
>  arch/arm/kvm/psci.c          | 1 +
>  arch/arm64/kvm/handle_exit.c | 1 +
>  3 files changed, 3 insertions(+)
> 
> diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
> index 96af65a30d78..ffb2406e5905 100644
> --- a/arch/arm/kvm/handle_exit.c
> +++ b/arch/arm/kvm/handle_exit.c
> @@ -72,6 +72,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		trace_kvm_wfx(*vcpu_pc(vcpu), false);
>  		vcpu->stat.wfi_exit_stat++;
>  		kvm_vcpu_block(vcpu);
> +		clear_bit(KVM_REQ_UNHALT, &vcpu->requests);

I actually don't understand the idea behind KVM_REQ_UNHALT?

It seems there's a semantic difference that architectures should adhere
by when returning from kvm_vcpu_block() with or without KVM_REQ_UNHALT
set (i.e. if the vcpu was runnable when kvm_vcpu_check_blocK() was
called?) - can you explain what the deal is?  Perhaps that belongs in
the documentation patch.

>  	}
>  
>  	kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
> index c2b131527a64..82fe7eb5b6a7 100644
> --- a/arch/arm/kvm/psci.c
> +++ b/arch/arm/kvm/psci.c
> @@ -57,6 +57,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
>  	 * for KVM will preserve the register state.
>  	 */
>  	kvm_vcpu_block(vcpu);
> +	clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
>  
>  	return PSCI_RET_SUCCESS;
>  }
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index fa1b18e364fc..e4937fb2fb89 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -89,6 +89,7 @@ static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
>  		vcpu->stat.wfi_exit_stat++;
>  		kvm_vcpu_block(vcpu);
> +		clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
>  	}
>  
>  	kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
> -- 
> 2.9.3
> 

Ignoring my comment above, for the content of this patch:

Acked-by: Christoffer Dall <cdall@linaro.org>