Subject: [PATCH v2 2/2] ARM/ARM64: KVM: Forward PSCI SYSTEM_OFF and SYSTEM_RESET to user space

From: [email-masked] (Christoffer Dall)
Date: Sat, 14 Dec 2013 11:28:43 -0800

On Sat, Dec 14, 2013 at 06:54:58PM +0530, Anup Patel wrote:
> On Sat, Dec 14, 2013 at 1:38 AM, Christoffer Dall
> <[email-masked]> wrote:
> > On Thu, Dec 12, 2013 at 09:42:27PM +0530, Anup Patel wrote:
> >> The PSCI SYSTEM_OFF and SYSTEM_RESET functions are system-level
> >> functions hence cannot be fully emulated by the in-kernel PSCI
> >> emulation code.
> >>
> >> To tackle this, we forward PSCI SYSTEM_OFF and SYSTEM_RESET function
> >> calls from vcpu to user space (i.e. QEMU or KVMTOOL) via kvm_run
> >> structure using KVM_EXIT_SYSTEM_EVENT exit reasons.
> >>
> >> Signed-off-by: Anup Patel <[email-masked]>
> >> Signed-off-by: Pranavkumar Sawargaonkar <[email-masked]>
> >> ---
> >>  arch/arm/include/asm/kvm_psci.h   |    2 +-
> >>  arch/arm/include/uapi/asm/kvm.h   |    2 ++
> >>  arch/arm/kvm/handle_exit.c        |   13 +++++++---
> >>  arch/arm/kvm/psci.c               |   48 ++++++++++++++++++++++++++++++-------
> >>  arch/arm64/include/asm/kvm_psci.h |    2 +-
> >>  arch/arm64/include/uapi/asm/kvm.h |    2 ++
> >>  arch/arm64/kvm/handle_exit.c      |   12 +++++++---
> >>  7 files changed, 65 insertions(+), 16 deletions(-)
> >>
> >> diff --git a/arch/arm/include/asm/kvm_psci.h b/arch/arm/include/asm/kvm_psci.h
> >> index 9a83d98..992d7f1 100644
> >> --- a/arch/arm/include/asm/kvm_psci.h
> >> +++ b/arch/arm/include/asm/kvm_psci.h
> >> @@ -18,6 +18,6 @@
> >>  #ifndef __ARM_KVM_PSCI_H__
> >>  #define __ARM_KVM_PSCI_H__
> >>
> >> -bool kvm_psci_call(struct kvm_vcpu *vcpu);
> >> +int 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 c498b60..f4de20c 100644
> >> --- a/arch/arm/include/uapi/asm/kvm.h
> >> +++ b/arch/arm/include/uapi/asm/kvm.h
> >> @@ -172,6 +172,8 @@ struct kvm_arch_memory_slot {
> >>  #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_FN_SYSTEM_OFF               KVM_PSCI_FN(4)
> >> +#define KVM_PSCI_FN_SYSTEM_RESET     KVM_PSCI_FN(5)
> >>
> >>  #define KVM_PSCI_RET_SUCCESS         0
> >>  #define KVM_PSCI_RET_NI                      ((unsigned long)-1)
> >> diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
> >> index a920790..c3f0e72 100644
> >> --- a/arch/arm/kvm/handle_exit.c
> >> +++ b/arch/arm/kvm/handle_exit.c
> >> @@ -40,14 +40,21 @@ static int handle_svc_hyp(struct kvm_vcpu *vcpu, struct kvm_run *run)
> >>
> >>  static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
> >>  {
> >> +     int ret;
> >> +
> >>       trace_kvm_hvc(*vcpu_pc(vcpu), *vcpu_reg(vcpu, 0),
> >>                     kvm_vcpu_hvc_get_imm(vcpu));
> >>
> >> -     if (kvm_psci_call(vcpu))
> >> +     ret = kvm_psci_call(vcpu);
> >> +     if (ret >= 0)
> >> +             return ret;
> >> +     else if (ret == -EINVAL) {
> >> +             kvm_inject_undefined(vcpu);
> >>               return 1;
> >> +     }
> >> +
> >> +     return ret;
> >
> > Wouldn't
> >
> > ret = kvm_psci_call(vcpu);
> > if (ret == -EINVAL) {
> >         kvm_inject_undefined(vcpu);
> >         return 1;
> > }
> >
> > return ret;
> >
> > be simpler?
> 
> Yes, I will make this simpler.
> 
> >
> > also, minor nit, but I think according to the CodingStyle if you have
> > single statements in if cases, but they are part of a larger if
> > statement with alternative clauses that use curly-brackets to
> > encapsulate multiple statements, then you should use curly braces around
> > the single-line statement as well...
> >
> >>
> >> -     kvm_inject_undefined(vcpu);
> >> -     return 1;
> >>  }
> >>
> >>  static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
> >> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
> >> index 0881bf1..8e246d6 100644
> >> --- a/arch/arm/kvm/psci.c
> >> +++ b/arch/arm/kvm/psci.c
> >> @@ -84,18 +84,41 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> >>       return KVM_PSCI_RET_SUCCESS;
> >>  }
> >>
> >> +static inline void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
> >> +{
> >> +     memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
> >> +     vcpu->run->system_event.type = type;
> >> +     vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
> >> +}
> >> +
> >> +static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
> >> +{
> >> +     kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN);
> >> +}
> >> +
> >> +static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
> >> +{
> >> +     kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
> >> +}
> >> +
> >>  /**
> >>   * kvm_psci_call - handle PSCI call if r0 value is in range
> >>   * @vcpu: Pointer to the VCPU struct
> >>   *
> >>   * Handle PSCI calls from guests through traps from HVC instructions.
> >> - * The calling convention is similar to SMC calls to the secure world where
> >> - * the function number is placed in r0 and this function returns true if the
> >> - * function number specified in r0 is withing the PSCI range, and false
> >> - * otherwise.
> >> + * The calling convention is similar to SMC calls to the secure world
> >> + * where the function number is placed in r0 and function number
> >
> > the function number
> >
> >> + * specified in r0 is withing the PSCI range.
> >
> > this reads a little funny now.  I think you can get rid of everything
> > after the first mention of r0 (cut from "and function number...") since
> > you explain that in the error codes below.
> 
> Sure, I will update this comment.
> 
> >
> >> + *
> >> + * This function returns: > 0 (success), 0 (success but exit to user
> >> + * space), and < 0 (errors)
> >
> > you could use @return: instead of "This function returns", but I'm not
> > sure if anyone actually cares.
> 
> Actually, "@returns" is correct way to specify as-per doxygen
> comment style for C but I have seen "Returns:" or "Returns" being
> used commonly in other parts of kernel. I will replace "The function
> returns:" with "Returns:".
> 

Yes, but it doesn't seem that's what the kernel preferred style is
following:

$ grep -sInR '@return' * | wc -l
583
$ grep -sInR '@returns' * | wc -l
82
$ grep -sInR '@Returns' * | wc -l
1
$ grep -sInR '@Return' * | wc -l
1

Anyway, it's not a big deal in any case.

[...]

-Christoffer