On Wed, 10 Apr 2024 18:54:37 +0100, Colton Lewis <coltonlewis@xxxxxxxxxx> wrote: > > Add an early_param to control WFx (WFI or WFE) trapping. This is so > interrupts can be passed through if the CPU has support for direct > interrupt injection, a feature of GICv4. This is described as an > enumeration with three possible behaviors, always passthrough (never > trap), never passthrough (always trap), or default (trap if more than > one task is running. Default matches the current behavior. > > Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx> > --- > v3: > * Changed control mechanism to an early_param on Marc's advice this should be > a system level decision and not exposed via uapi > * Reduced behavior to an enum from an integer as there are only a few options > that make logical sense > * Limit option for always passthrough to systems with GICv4 since the primary > case for always passthrough is systems with direct interrupt injection > > v2: > https://lore.kernel.org/kvmarm/20240319164341.1674863-1-coltonlewis@xxxxxxxxxx/ > > v1: > https://lore.kernel.org/kvmarm/20240129213918.3124494-1-coltonlewis@xxxxxxxxxx/ > > arch/arm64/include/asm/kvm_host.h | 7 +++++++ > arch/arm64/kvm/arm.c | 30 +++++++++++++++++++++++++++++- > 2 files changed, 36 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 21c57b812569..e9225b1d0e9b 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -67,6 +67,13 @@ enum kvm_mode { > KVM_MODE_NV, > KVM_MODE_NONE, > }; > + > +enum kvm_interrupt_passthrough { > + KVM_INTERRUPT_PASSTHROUGH_DEFAULT, > + KVM_INTERRUPT_PASSTHROUGH_ALWAYS, > + KVM_INTERRUPT_PASSTHROUGH_NEVER, What does this mean? This is not dealing with interrupts, this is supposed to deal with the behaviour of specific instructions (WFI/WFE). The notion of "passthrough" is really odd as well. Finally, both ALWAYS and NEVER are wrong -- the architecture makes no such guarantee. > +}; > + > #ifdef CONFIG_KVM > enum kvm_mode kvm_get_mode(void); > #else > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index a25265aca432..5d0ea6b2c652 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -46,6 +46,7 @@ > #include <kvm/arm_psci.h> > > static enum kvm_mode kvm_mode = KVM_MODE_DEFAULT; > +static enum kvm_interrupt_passthrough kvm_interrupt_passthrough = KVM_INTERRUPT_PASSTHROUGH_DEFAULT; > > DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector); > > @@ -456,7 +457,10 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > if (kvm_arm_is_pvtime_enabled(&vcpu->arch)) > kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu); > > - if (single_task_running()) > + if ((kvm_interrupt_passthrough == KVM_INTERRUPT_PASSTHROUGH_ALWAYS > + && kvm_vgic_global_state.has_gicv4) || > + (kvm_interrupt_passthrough == KVM_INTERRUPT_PASSTHROUGH_DEFAULT > + && single_task_running())) Why is this affecting both WFI and WFE? They are very different and lumping them together makes little sense. > vcpu_clear_wfx_traps(vcpu); > else > vcpu_set_wfx_traps(vcpu); > @@ -2654,6 +2658,30 @@ static int __init early_kvm_mode_cfg(char *arg) > } > early_param("kvm-arm.mode", early_kvm_mode_cfg); > > +static int __init early_kvm_interrupt_passthrough_cfg(char *arg) > +{ > + if (!arg) > + return -EINVAL; > + > + if (strcmp(arg, "always") == 0) { > + kvm_interrupt_passthrough = KVM_INTERRUPT_PASSTHROUGH_ALWAYS; > + return 0; > + } > + > + if (strcmp(arg, "never") == 0) { > + kvm_interrupt_passthrough = KVM_INTERRUPT_PASSTHROUGH_NEVER; > + return 0; > + } > + > + if (strcmp(arg, "default") == 0) { > + kvm_interrupt_passthrough = KVM_INTERRUPT_PASSTHROUGH_DEFAULT; > + return 0; > + } > + > + return -EINVAL; > +} > +early_param("kvm-arm.interrupt-passthrough", early_kvm_interrupt_passthrough_cfg); > + Again, this is not dealing with interrupts. This is dealing with the *potential* trapping of instructions in certain circumstances. > enum kvm_mode kvm_get_mode(void) > { > return kvm_mode; Finally, this needs to be documented. Thanks, M. -- Without deviation from the norm, progress is not possible.
