| Message ID | 1396262773-7723-12-git-send-email-anup.patel@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Mon, Mar 31, 2014 at 04:16:12PM +0530, Anup Patel wrote: > This patch adds emulation of PSCI v0.2 CPU_SUSPEND function call for > KVM ARM/ARM64. This is a CPU-level function call which can suspend > current CPU or current CPU cluster. We don't have VCPU clusters in > KVM so for KVM we simply suspend the current VCPU. > > The CPU_SUSPEND emulation is not tested much because currently there > is no CPUIDLE driver in Linux kernel that uses PSCI CPU_SUSPEND. The > PSCI CPU_SUSPEND implementation in ARM64 kernel was tested using a > Simple CPUIDLE driver which is not published due to unstable DT-bindings > for PSCI. > (For more info, http://lwn.net/Articles/574950/) > > Even if we had stable DT-bindings for PSCI and CPUIDLE driver that > uses PSCI CPU_SUSPEND then still we need to define SUSPEND states > and WAKEUP events for KVM ARM/ARM64. > > Due to this, we implement CPU_SUSPEND emulation similar to WFI > (Wait-for-interrupt) emulation. > > Signed-off-by: Anup Patel <anup.patel@linaro.org> > Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org> > --- > arch/arm/kvm/psci.c | 29 +++++++++++++++++++++++++---- > 1 file changed, 25 insertions(+), 4 deletions(-) > > diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c > index 85bf896..f414fd3 100644 > --- a/arch/arm/kvm/psci.c > +++ b/arch/arm/kvm/psci.c > @@ -52,6 +52,27 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level) > return affinity_mask; > } > > +static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu) > +{ > + /* > + * NOTE: Currently, we don't have any wakeup events for KVM > + * so for simplicity we make VCPU suspend emulation same-as > + * WFI (Wait-for-interrupt) emulation. If you implement it like WFI, we do have wake-up events: Namely interrupts. > + * > + * To do this we simply update VCPU registers as-per state > + * info provided via r1 - r3 (or x1 - x3) and block the > + * VCPU for irqs. > + */ > + if (*vcpu_reg(vcpu, 1) & (0x1UL << 16)) { > + /* Update return pc and r0 for power-down state. */ > + *vcpu_pc(vcpu) = *vcpu_reg(vcpu, 2); > + *vcpu_reg(vcpu, 0) = *vcpu_reg(vcpu, 3); > + } Hmm, this looks wrong. This looks like you're respecting the power-down state request but not resetting the CPU. What I was saying before was that if you implement this as kvm_vcpu_block(), just like WFI, then you need to preserve all state, ignore power-down state requests and treat them as suspend states, implement them as WFI, and put a big fat comment here explaining why this is architecturally valid (by referring to the PSCI 0.2 spec) and what the semantics of doing that is. -Christoffer > + kvm_vcpu_block(vcpu); > + > + return PSCI_RET_SUCCESS; > +} > + > static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu) > { > vcpu->arch.pause = true; > @@ -195,6 +216,10 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) > */ > val = 2; > break; > + case PSCI_0_2_FN_CPU_SUSPEND: > + case PSCI_0_2_FN64_CPU_SUSPEND: > + val = kvm_psci_vcpu_suspend(vcpu); > + break; > case PSCI_0_2_FN_CPU_OFF: > kvm_psci_vcpu_off(vcpu); > val = PSCI_RET_SUCCESS; > @@ -232,10 +257,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) > val = PSCI_RET_SUCCESS; > ret = 0; > break; > - case PSCI_0_2_FN_CPU_SUSPEND: > - case PSCI_0_2_FN64_CPU_SUSPEND: > - val = PSCI_RET_NOT_SUPPORTED; > - break; > default: > return -EINVAL; > } > -- > 1.7.9.5 >
On Mon, Mar 31, 2014 at 11:10 PM, Christoffer Dall <christoffer.dall@linaro.org> wrote: > On Mon, Mar 31, 2014 at 04:16:12PM +0530, Anup Patel wrote: >> This patch adds emulation of PSCI v0.2 CPU_SUSPEND function call for >> KVM ARM/ARM64. This is a CPU-level function call which can suspend >> current CPU or current CPU cluster. We don't have VCPU clusters in >> KVM so for KVM we simply suspend the current VCPU. >> >> The CPU_SUSPEND emulation is not tested much because currently there >> is no CPUIDLE driver in Linux kernel that uses PSCI CPU_SUSPEND. The >> PSCI CPU_SUSPEND implementation in ARM64 kernel was tested using a >> Simple CPUIDLE driver which is not published due to unstable DT-bindings >> for PSCI. >> (For more info, http://lwn.net/Articles/574950/) >> >> Even if we had stable DT-bindings for PSCI and CPUIDLE driver that >> uses PSCI CPU_SUSPEND then still we need to define SUSPEND states >> and WAKEUP events for KVM ARM/ARM64. >> >> Due to this, we implement CPU_SUSPEND emulation similar to WFI >> (Wait-for-interrupt) emulation. >> >> Signed-off-by: Anup Patel <anup.patel@linaro.org> >> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org> >> --- >> arch/arm/kvm/psci.c | 29 +++++++++++++++++++++++++---- >> 1 file changed, 25 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c >> index 85bf896..f414fd3 100644 >> --- a/arch/arm/kvm/psci.c >> +++ b/arch/arm/kvm/psci.c >> @@ -52,6 +52,27 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level) >> return affinity_mask; >> } >> >> +static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu) >> +{ >> + /* >> + * NOTE: Currently, we don't have any wakeup events for KVM >> + * so for simplicity we make VCPU suspend emulation same-as >> + * WFI (Wait-for-interrupt) emulation. > > If you implement it like WFI, we do have wake-up events: Namely > interrupts. > >> + * >> + * To do this we simply update VCPU registers as-per state >> + * info provided via r1 - r3 (or x1 - x3) and block the >> + * VCPU for irqs. >> + */ >> + if (*vcpu_reg(vcpu, 1) & (0x1UL << 16)) { >> + /* Update return pc and r0 for power-down state. */ >> + *vcpu_pc(vcpu) = *vcpu_reg(vcpu, 2); >> + *vcpu_reg(vcpu, 0) = *vcpu_reg(vcpu, 3); >> + } > > > Hmm, this looks wrong. This looks like you're respecting the power-down > state request but not resetting the CPU. What I was saying before was > that if you implement this as kvm_vcpu_block(), just like WFI, then you > need to preserve all state, ignore power-down state requests and treat > them as suspend states, implement them as WFI, and put a big fat comment > here explaining why this is architecturally valid (by referring to the > PSCI 0.2 spec) and what the semantics of doing that is. Actually, I was more inclined towards preserving the VCPU context for power-down request but as-per section 5.4.2 clause 3 we can treat power-down request to be same as suspend request. I update this patch accordingly. Regards, Anup > > -Christoffer > > >> + kvm_vcpu_block(vcpu); >> + >> + return PSCI_RET_SUCCESS; >> +} >> + >> static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu) >> { >> vcpu->arch.pause = true; >> @@ -195,6 +216,10 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) >> */ >> val = 2; >> break; >> + case PSCI_0_2_FN_CPU_SUSPEND: >> + case PSCI_0_2_FN64_CPU_SUSPEND: >> + val = kvm_psci_vcpu_suspend(vcpu); >> + break; >> case PSCI_0_2_FN_CPU_OFF: >> kvm_psci_vcpu_off(vcpu); >> val = PSCI_RET_SUCCESS; >> @@ -232,10 +257,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) >> val = PSCI_RET_SUCCESS; >> ret = 0; >> break; >> - case PSCI_0_2_FN_CPU_SUSPEND: >> - case PSCI_0_2_FN64_CPU_SUSPEND: >> - val = PSCI_RET_NOT_SUPPORTED; >> - break; >> default: >> return -EINVAL; >> } >> -- >> 1.7.9.5 >> > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c index 85bf896..f414fd3 100644 --- a/arch/arm/kvm/psci.c +++ b/arch/arm/kvm/psci.c @@ -52,6 +52,27 @@ static unsigned long psci_affinity_mask(unsigned long affinity_level) return affinity_mask; } +static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu) +{ + /* + * NOTE: Currently, we don't have any wakeup events for KVM + * so for simplicity we make VCPU suspend emulation same-as + * WFI (Wait-for-interrupt) emulation. + * + * To do this we simply update VCPU registers as-per state + * info provided via r1 - r3 (or x1 - x3) and block the + * VCPU for irqs. + */ + if (*vcpu_reg(vcpu, 1) & (0x1UL << 16)) { + /* Update return pc and r0 for power-down state. */ + *vcpu_pc(vcpu) = *vcpu_reg(vcpu, 2); + *vcpu_reg(vcpu, 0) = *vcpu_reg(vcpu, 3); + } + kvm_vcpu_block(vcpu); + + return PSCI_RET_SUCCESS; +} + static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu) { vcpu->arch.pause = true; @@ -195,6 +216,10 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) */ val = 2; break; + case PSCI_0_2_FN_CPU_SUSPEND: + case PSCI_0_2_FN64_CPU_SUSPEND: + val = kvm_psci_vcpu_suspend(vcpu); + break; case PSCI_0_2_FN_CPU_OFF: kvm_psci_vcpu_off(vcpu); val = PSCI_RET_SUCCESS; @@ -232,10 +257,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) val = PSCI_RET_SUCCESS; ret = 0; break; - case PSCI_0_2_FN_CPU_SUSPEND: - case PSCI_0_2_FN64_CPU_SUSPEND: - val = PSCI_RET_NOT_SUPPORTED; - break; default: return -EINVAL; }