[PATCH 2/2] ARM/ARM64: KVM: Forward PSCI SYSTEM_OFF and SYSTEM_RESET to user space
Anup Patel
anup at brainfault.org
Tue Dec 10 00:05:21 EST 2013
On Tue, Dec 10, 2013 at 4:21 AM, Christoffer Dall
<christoffer.dall at linaro.org> wrote:
> On Mon, Nov 25, 2013 at 09:19:59PM +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 guest to user space (i.e. QEMU or KVMTOOL) via KVM run
>> structure using KVM_EXIT_SHUTDOWN and KVM_EXIT_RESET exit reasons.
>>
>> Signed-off-by: Anup Patel <anup.patel at linaro.org>
>> Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar at linaro.org>
>> ---
>> arch/arm/include/asm/kvm_psci.h | 2 +-
>> arch/arm/include/uapi/asm/kvm.h | 2 ++
>> arch/arm/kvm/handle_exit.c | 7 ++++++-
>> arch/arm/kvm/psci.c | 38 +++++++++++++++++++++++++++++--------
>> arch/arm64/include/asm/kvm_psci.h | 2 +-
>> arch/arm64/include/uapi/asm/kvm.h | 2 ++
>> arch/arm64/kvm/handle_exit.c | 10 ++++++----
>> 7 files changed, 48 insertions(+), 15 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..c96c7e8 100644
>> --- a/arch/arm/kvm/handle_exit.c
>> +++ b/arch/arm/kvm/handle_exit.c
>> @@ -40,11 +40,16 @@ 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 1;
>> + else if (ret > 0)
>> + return 0;
>>
>> kvm_inject_undefined(vcpu);
>> return 1;
>> diff --git a/arch/arm/kvm/psci.c b/arch/arm/kvm/psci.c
>> index 0881bf1..c8d3fcd 100644
>> --- a/arch/arm/kvm/psci.c
>> +++ b/arch/arm/kvm/psci.c
>> @@ -84,18 +84,31 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>> return KVM_PSCI_RET_SUCCESS;
>> }
>>
>> +static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
>> +{
>> + vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
>> +}
>> +
>> +static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
>> +{
>> + vcpu->run->exit_reason = KVM_EXIT_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
>> + * specified in r0 is withing the PSCI range.
>> + *
>> + * This function returns: 0 (success), > 0 (success but exit to user
>> + * space), and < 0 (failure)
>
> Hmmm, I think this is a bit confusing because it essentially does the
> reverse of all the other kvm internal return convention. Wouldn't it
> make more sense to have 0 (success, but exit to user space), 1 (success,
> resume VM), and < 0 (failure).
OK, I will change kvm_psci_call() return convention as-per your suggestion.
>
> Also note that you are general-casing all error codes that may happen to
> mean that it did not match the PSCI function to anything well-known.
> In this case, that's sort of ok, because we don't expect the PSCI code
> to randomly fail (if it does, it reports it to the caller in the return
> register), but not fail, as in, I'm out of memory or anything like that.
> But I think you can clarify this in the comment, by saying something
> like:
>
> Errors:
> -EINVAL: Unrecognized PSCI function
Sure, I will update the comments.
>
> in the comment for the function.
>
>> */
>> -bool kvm_psci_call(struct kvm_vcpu *vcpu)
>> +int kvm_psci_call(struct kvm_vcpu *vcpu)
>> {
>> + int ret = 0;
>> unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
>> unsigned long val;
>>
>> @@ -111,11 +124,20 @@ bool kvm_psci_call(struct kvm_vcpu *vcpu)
>> case KVM_PSCI_FN_MIGRATE:
>> val = KVM_PSCI_RET_NI;
>> break;
>> -
>> + case KVM_PSCI_FN_SYSTEM_OFF:
>> + kvm_psci_system_off(vcpu);
>> + val = KVM_PSCI_RET_SUCCESS;
>> + ret = 1;
>> + break;
>> + case KVM_PSCI_FN_SYSTEM_RESET:
>> + kvm_psci_system_reset(vcpu);
>> + val = KVM_PSCI_RET_SUCCESS;
>> + ret = 1;
>> + break;
>> default:
>> - return false;
>> + return -EINVAL;
>> }
>>
>> *vcpu_reg(vcpu, 0) = val;
>> - return true;
>> + return ret;
>> }
>> diff --git a/arch/arm64/include/asm/kvm_psci.h b/arch/arm64/include/asm/kvm_psci.h
>> index e301a48..9bd0ee8 100644
>> --- a/arch/arm64/include/asm/kvm_psci.h
>> +++ b/arch/arm64/include/asm/kvm_psci.h
>> @@ -18,6 +18,6 @@
>> #ifndef __ARM64_KVM_PSCI_H__
>> #define __ARM64_KVM_PSCI_H__
>>
>> -bool kvm_psci_call(struct kvm_vcpu *vcpu);
>> +int kvm_psci_call(struct kvm_vcpu *vcpu);
>>
>> #endif /* __ARM64_KVM_PSCI_H__ */
>> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
>> index d9f026b..f678902 100644
>> --- a/arch/arm64/include/uapi/asm/kvm.h
>> +++ b/arch/arm64/include/uapi/asm/kvm.h
>> @@ -158,6 +158,8 @@ 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/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
>> index 8da5606..a5b5b6a 100644
>> --- a/arch/arm64/kvm/handle_exit.c
>> +++ b/arch/arm64/kvm/handle_exit.c
>> @@ -30,8 +30,13 @@ typedef int (*exit_handle_fn)(struct kvm_vcpu *, struct kvm_run *);
>>
>> static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> {
>> - if (kvm_psci_call(vcpu))
>> + int ret;
>> +
>> + ret = kvm_psci_call(vcpu);
>> + if (ret == 0)
>> return 1;
>> + else if (ret > 0)
>> + return 0;
>>
>> kvm_inject_undefined(vcpu);
>> return 1;
>> @@ -39,9 +44,6 @@ 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))
>> - return 1;
>> -
>
> Isn't this an unrelated change, which should go in a separate patch with
> some justification text for the change?
Actually, handle_smc() was already using kvm_psci_call() so I had to change
it anyway because of changes in kvm_psic_call(). Also, user space emulation
of SMC-based PSCI is going to be different from in-kernel HVC-based PSCI
emulation hence, for now it seemed more appropriate to inject undefined
exception for KVM arm64 (just like KVM arm).
--
Anup
>
>> kvm_inject_undefined(vcpu);
>> return 1;
>> }
>> --
>> 1.7.9.5
>>
>
> Otherwise, it looks overall to go in the right direction.
>
> -Christoffer
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