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From: Oliver Upton To: Colton Lewis Cc: kvm@vger.kernel.org, Jonathan Corbet , Marc Zyngier , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v6] KVM: arm64: Add early_param to control WFx trapping Message-ID: References: <20240523174056.1565133-1-coltonlewis@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240523174056.1565133-1-coltonlewis@google.com> X-Migadu-Flow: FLOW_OUT On Thu, May 23, 2024 at 05:40:55PM +0000, Colton Lewis wrote: > Add an early_params to control WFI and WFE trapping. This is to > control the degree guests can wait for interrupts on their own without > being trapped by KVM. Options for each param are trap and notrap. trap > enables the trap. notrap disables the trap. Note that when enabled, > traps are allowed but not guaranteed by the CPU architecture. Absent > an explicitly set policy, default to current behavior: disabling the > trap if only a single task is running and enabling otherwise. > > Signed-off-by: Colton Lewis > --- > v6: > * Rebase to v6.9.1 As in from the stable tree? Please base your patches on an -rc tag, and especially one from this release cycle. > +static bool kvm_vcpu_should_clear_twi(struct kvm_vcpu *vcpu) > +{ > + if (likely(kvm_wfi_trap_policy == KVM_WFX_NOTRAP_SINGLE_TASK)) > + return single_task_running() && > + (atomic_read(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count) || > + vcpu->kvm->arch.vgic.nassgireq); > + > + return kvm_wfi_trap_policy == KVM_WFX_NOTRAP; > +} Generally, it is more readable to organize your code in such a way that multiline statements are unnested as much as possible. So if you were to invert the if condition it'd become a bit cleaner. Here is what I plan on squashing into this patch, kvm_vcpu_should_clear_twe() got the same treatment for the sake of consistency. diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 9cddd1096b0a..53e23528d2cf 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -557,20 +557,20 @@ static void vcpu_set_pauth_traps(struct kvm_vcpu *vcpu) static bool kvm_vcpu_should_clear_twi(struct kvm_vcpu *vcpu) { - if (likely(kvm_wfi_trap_policy == KVM_WFX_NOTRAP_SINGLE_TASK)) - return single_task_running() && - (atomic_read(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count) || - vcpu->kvm->arch.vgic.nassgireq); + if (unlikely(kvm_wfi_trap_policy != KVM_WFX_NOTRAP_SINGLE_TASK)) + return kvm_wfi_trap_policy == KVM_WFX_NOTRAP; - return kvm_wfi_trap_policy == KVM_WFX_NOTRAP; + return single_task_running() && + (atomic_read(&vcpu->arch.vgic_cpu.vgic_v3.its_vpe.vlpi_count) || + vcpu->kvm->arch.vgic.nassgireq); } static bool kvm_vcpu_should_clear_twe(struct kvm_vcpu *vcpu) { - if (likely(kvm_wfe_trap_policy == KVM_WFX_NOTRAP_SINGLE_TASK)) - return single_task_running(); + if (unlikely(kvm_wfe_trap_policy != KVM_WFX_NOTRAP_SINGLE_TASK)) + return kvm_wfe_trap_policy == KVM_WFX_NOTRAP; - return kvm_wfe_trap_policy == KVM_WFX_NOTRAP; + return single_task_running(); } void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) -- Thanks, Oliver