Re: [PATCH v6 14/15] KVM: ARM: Power State Coordination Interface implementation

Gleb Natapov
2013-01-21T13:53:12Z

On Sun, Jan 20, 2013 at 06:35:51PM -0500, Christoffer Dall wrote:
> On Thu, Jan 17, 2013 at 10:55 AM, Marc Zyngier <marc.zyngier@arm.com> wrote:
> > On 16/01/13 17:59, Christoffer Dall wrote:
> >> From: Marc Zyngier <marc.zyngier@arm.com>
> >>
> >> Implement the PSCI specification (ARM DEN 0022A) to control
> >> virtual CPUs being "powered" on or off.
> >>
> >> PSCI/KVM is detected using the KVM_CAP_ARM_PSCI capability.
> >>
> >> A virtual CPU can now be initialized in a "powered off" state,
> >> using the KVM_ARM_VCPU_POWER_OFF feature flag.
> >>
> >> The guest can use either SMC or HVC to execute a PSCI function.
> >>
> >> Reviewed-by: Will Deacon <will.deacon@arm.com>
> >> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> >> Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
> >
> > A few bits went wrong when you reworked this patch. See below.
> >
> >> ---
> >> Documentation/virtual/kvm/api.txt | 4 +
> >> arch/arm/include/asm/kvm_emulate.h | 5 ++
> >> arch/arm/include/asm/kvm_host.h | 5 +-
> >> arch/arm/include/asm/kvm_psci.h | 23 ++++++++
> >> arch/arm/include/uapi/asm/kvm.h | 16 +++++
> >> arch/arm/kvm/Makefile | 2 -
> >> arch/arm/kvm/arm.c | 28 +++++++++-
> >> arch/arm/kvm/psci.c | 105 ++++++++++++++++++++++++++++++++++++
> >> include/uapi/linux/kvm.h | 1
> >> 9 files changed, 184 insertions(+), 5 deletions(-)
> >> create mode 100644 arch/arm/include/asm/kvm_psci.h
> >> create mode 100644 arch/arm/kvm/psci.c
> >>
> >> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> >> index 38066a7a..c25439a 100644
> >> --- a/Documentation/virtual/kvm/api.txt
> >> +++ b/Documentation/virtual/kvm/api.txt
> >> @@ -2185,6 +2185,10 @@ return ENOEXEC for that vcpu.
> >> Note that because some registers reflect machine topology, all vcpus
> >> should be created before this ioctl is invoked.
> >>
> >> +Possible features:
> >> + - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
> >> + Depends on KVM_CAP_ARM_PSCI.
> >> +
> >>
> >> 4.78 KVM_GET_REG_LIST
> >>
> >> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
> >> index 4c1a073..ba07de9 100644
> >> --- a/arch/arm/include/asm/kvm_emulate.h
> >> +++ b/arch/arm/include/asm/kvm_emulate.h
> >> @@ -32,6 +32,11 @@ void kvm_inject_undefined(struct kvm_vcpu *vcpu);
> >> void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
> >> void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
> >>
> >> +static inline bool vcpu_mode_is_32bit(struct kvm_vcpu *vcpu)
> >> +{
> >> + return 1;
> >> +}
> >> +
> >> static inline u32 *vcpu_pc(struct kvm_vcpu *vcpu)
> >> {
> >> return (u32 *)&vcpu->arch.regs.usr_regs.ARM_pc;
> >> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> >> index e65fc96..c9ba918 100644
> >> --- a/arch/arm/include/asm/kvm_host.h
> >> +++ b/arch/arm/include/asm/kvm_host.h
> >> @@ -30,7 +30,7 @@
> >> #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
> >> #define KVM_HAVE_ONE_REG
> >>
> >> -#define KVM_VCPU_MAX_FEATURES 0
> >> +#define KVM_VCPU_MAX_FEATURES 1
> >>
> >> /* We don't currently support large pages. */
> >> #define KVM_HPAGE_GFN_SHIFT(x) 0
> >> @@ -100,6 +100,9 @@ struct kvm_vcpu_arch {
> >> int last_pcpu;
> >> cpumask_t require_dcache_flush;
> >>
> >> + /* Don't run the guest: see copy_current_insn() */
> >
> > Now that you made this field PSCI-specific, how about rewording the comment?
> >
>
> yeah, that would work. And actually it's kind of broken, because if we
> sent a paused VCPU a signal and that VCPU is never woken up using the
> PSCI call we'll busy spin in the kernel, which is sad :(
>
> This should eventually be moved to the vcpu requests infrastructure,
> but I'll send some preparatory patches to the kvm first, so let's fix
> it in the right way later on (requires reworking the run loop quite a
> bit), and for now simply fix the pause clause, see patch below.
>
> >> + bool pause;
> >> +
> >> /* IO related fields */
> >> struct kvm_decode mmio_decode;
> >>
> >> diff --git a/arch/arm/include/asm/kvm_psci.h b/arch/arm/include/asm/kvm_psci.h
> >> new file mode 100644
> >> index 0000000..9a83d98
> >> --- /dev/null
> >> +++ b/arch/arm/include/asm/kvm_psci.h
> >> @@ -0,0 +1,23 @@
> >> +/*
> >> + * Copyright (C) 2012 - ARM Ltd
> >> + * Author: Marc Zyngier <marc.zyngier@arm.com>
> >> + *
> >> + * This program is free software; you can redistribute it and/or modify
> >> + * it under the terms of the GNU General Public License version 2 as
> >> + * published by the Free Software Foundation.
> >> + *
> >> + * This program is distributed in the hope that it will be useful,
> >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> >> + * GNU General Public License for more details.
> >> + *
> >> + * You should have received a copy of the GNU General Public License
> >> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> >> + */
> >> +
> >> +#ifndef __ARM_KVM_PSCI_H__
> >> +#define __ARM_KVM_PSCI_H__
> >> +
> >> +bool kvm_psci_call(struct kvm_vcpu *vcpu);
> >> +
> >> +#endif /* __ARM_KVM_PSCI_H__ */
> >> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
> >> index bbb6b23..3303ff5 100644
> >> --- a/arch/arm/include/uapi/asm/kvm.h
> >> +++ b/arch/arm/include/uapi/asm/kvm.h
> >> @@ -65,6 +65,8 @@ struct kvm_regs {
> >> #define KVM_ARM_TARGET_CORTEX_A15 0
> >> #define KVM_ARM_NUM_TARGETS 1
> >>
> >> +#define KVM_ARM_VCPU_POWER_OFF 0 /* CPU is started in OFF state */
> >> +
> >> struct kvm_vcpu_init {
> >> __u32 target;
> >> __u32 features[7];
> >> @@ -145,4 +147,18 @@ struct kvm_arch_memory_slot {
> >> /* Highest supported SPI, from VGIC_NR_IRQS */
> >> #define KVM_ARM_IRQ_GIC_MAX 127
> >>
> >> +/* PSCI interface */
> >> +#define KVM_PSCI_FN_BASE 0x95c1ba5e
> >> +#define KVM_PSCI_FN(n) (KVM_PSCI_FN_BASE + (n))
> >> +
> >> +#define KVM_PSCI_FN_CPU_SUSPEND KVM_PSCI_FN(0)
> >> +#define KVM_PSCI_FN_CPU_OFF KVM_PSCI_FN(1)
> >> +#define KVM_PSCI_FN_CPU_ON KVM_PSCI_FN(2)
> >> +#define KVM_PSCI_FN_MIGRATE KVM_PSCI_FN(3)
> >> +
> >> +#define KVM_PSCI_RET_SUCCESS 0
> >> +#define KVM_PSCI_RET_NI ((unsigned long)-1)
> >> +#define KVM_PSCI_RET_INVAL ((unsigned long)-2)
> >> +#define KVM_PSCI_RET_DENIED ((unsigned long)-3)
> >> +
> >> #endif /* __ARM_KVM_H__ */
> >> diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
> >> index 1e45cd9..ea27987 100644
> >> --- a/arch/arm/kvm/Makefile
> >> +++ b/arch/arm/kvm/Makefile
> >> @@ -18,4 +18,4 @@ kvm-arm-y = $(addprefix ../../../virt/kvm/, kvm_main.o coalesced_mmio.o)
> >>
> >> obj-y += kvm-arm.o init.o interrupts.o
> >> obj-y += arm.o guest.o mmu.o emulate.o reset.o
> >> -obj-y += coproc.o coproc_a15.o mmio.o
> >> +obj-y += coproc.o coproc_a15.o mmio.o psci.o
> >> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> >> index 3168b9d..6ff5337 100644
> >> --- a/arch/arm/kvm/arm.c
> >> +++ b/arch/arm/kvm/arm.c
> >> @@ -43,6 +43,7 @@
> >> #include <asm/kvm_mmu.h>
> >> #include <asm/kvm_emulate.h>
> >> #include <asm/kvm_coproc.h>
> >> +#include <asm/kvm_psci.h>
> >> #include <asm/opcodes.h>
> >>
> >> #ifdef REQUIRES_VIRT
> >> @@ -160,6 +161,7 @@ int kvm_dev_ioctl_check_extension(long ext)
> >> case KVM_CAP_SYNC_MMU:
> >> case KVM_CAP_DESTROY_MEMORY_REGION_WORKS:
> >> case KVM_CAP_ONE_REG:
> >> + case KVM_CAP_ARM_PSCI:
> >> r = 1;
> >> break;
> >> case KVM_CAP_COALESCED_MMIO:
> >> @@ -443,13 +445,17 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
> >> trace_kvm_hvc(*vcpu_pc(vcpu), *vcpu_reg(vcpu, 0),
> >> vcpu->arch.hsr & HSR_HVC_IMM_MASK);
> >>
> >> + if (kvm_psci_call(vcpu))
> >> + return 1;
> >> +
> >> return 1;
> >
> > No undef injection if there is no PSCI match?
> >
> >> }
> >>
> >> static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
> >> {
> >> - /* We don't support SMC; don't do that. */
> >> - kvm_debug("smc: at %08x", *vcpu_pc(vcpu));
> >> + if (!kvm_psci_call(vcpu))
> >
> > Looks like you got the return value backward here.
> >
>
> yeah, I missed that call completely.
>
> >> + return 1;
> >> +
> >> kvm_inject_undefined(vcpu);
> >> return 1;
> >> }
> >
> Thanks, see this patch:
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 751aa86..d1736a5 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -113,7 +113,7 @@ struct kvm_vcpu_arch {
> int last_pcpu;
> cpumask_t require_dcache_flush;
>
> - /* Don't run the guest: see copy_current_insn() */
> + /* Don't run the guest on this vcpu */
> bool pause;
>
> /* IO related fields */
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index a67392a..2819575 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -502,7 +502,7 @@ static int handle_hvc(struct kvm_vcpu *vcpu,
> struct kvm_run *run)
>
> static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
> {
> - if (!kvm_psci_call(vcpu))
> + if (kvm_psci_call(vcpu))
> return 1;
>
> kvm_inject_undefined(vcpu);
> @@ -667,6 +667,13 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> +static void vcpu_pause(struct kvm_vcpu *vcpu)
> +{
> + wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
> +
> + wait_event_interruptible(*wq, !vcpu->arch.pause);
> +}
> +
> /**
> * kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
> * @vcpu: The VCPU pointer
> @@ -710,6 +717,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu,
> struct kvm_run *run)
>
> update_vttbr(vcpu->kvm);
>
> + if (vcpu->arch.pause)
> + vcpu_pause(vcpu);
> +
If you check vcpu->arch.pause in kvm_arch_vcpu_runnable() you can use
kvm_vcpu_block() here.

> kvm_vgic_flush_hwstate(vcpu);
> kvm_timer_flush_hwstate(vcpu);
>
> @@ -737,13 +747,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu
> *vcpu, struct kvm_run *run)
> kvm_guest_enter();
> vcpu->mode = IN_GUEST_MODE;
>
> - smp_mb(); /* set mode before reading vcpu->arch.pause */
> - if (unlikely(vcpu->arch.pause)) {
> - /* This means ignore, try again. */
> - ret = ARM_EXCEPTION_IRQ;
> - } else {
> - ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
> - }
> + ret = kvm_call_hyp(__kvm_vcpu_run, vcpu);
>
> vcpu->mode = OUTSIDE_GUEST_MODE;
> vcpu->arch.last_pcpu = smp_processor_id();
> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
> index 6be3687..d833604 100644
> --- a/arch/arm/kvm/psci.c
> +++ b/arch/arm/kvm/psci.c
> @@ -28,11 +28,7 @@
>
> static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
> {
> - wait_queue_head_t *wq = kvm_arch_vcpu_wq(vcpu);
> -
> vcpu->arch.pause = true;
> -
> - wait_event_interruptible(*wq, !vcpu->arch.pause);
> }
>
> static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> --
> 1.7.9.5
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--
Gleb.