| Message ID | 20240410175437.793508-1-coltonlewis@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] KVM: arm64: Add early_param to control WFx trapping | expand |
On Wed, 10 Apr 2024 18:54:37 +0100, Colton Lewis <coltonlewis@google.com> 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@google.com> > --- > 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@google.com/ > > v1: > https://lore.kernel.org/kvmarm/20240129213918.3124494-1-coltonlewis@google.com/ > > 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.
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, +}; + #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())) 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); + enum kvm_mode kvm_get_mode(void) { return kvm_mode;
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@google.com> --- 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@google.com/ v1: https://lore.kernel.org/kvmarm/20240129213918.3124494-1-coltonlewis@google.com/ arch/arm64/include/asm/kvm_host.h | 7 +++++++ arch/arm64/kvm/arm.c | 30 +++++++++++++++++++++++++++++- 2 files changed, 36 insertions(+), 1 deletion(-) -- 2.44.0.478.gd926399ef9-goog