[RFC PATCH 2/5] ARM/ARM64: KVM: Forward PSCI SYSTEM_OFF and SYSTEM_RESET to user space
Anup Patel
anup at brainfault.org
Thu Oct 17 01:52:21 EDT 2013
On Thu, Oct 17, 2013 at 3:52 AM, Christoffer Dall
<christoffer.dall at linaro.org> wrote:
> On Wed, Oct 16, 2013 at 10:32:31PM +0530, Anup Patel wrote:
>> The PSCI SYSTEM_OFF and SYSTEM_RESET functions are VM or Guest level
>> functions hence cannot be 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 with KVM_EXIT_PSCI exit reason.
>>
>> 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 | 25 +++++++++++++++-
>> arch/arm/include/uapi/asm/kvm.h | 2 ++
>> arch/arm/kvm/arm.c | 12 ++++++--
>> arch/arm/kvm/handle_exit.c | 12 ++++++--
>> arch/arm/kvm/psci.c | 57 ++++++++++++++++++++++++++++++++++---
>> arch/arm64/include/asm/kvm_psci.h | 25 +++++++++++++++-
>> arch/arm64/include/uapi/asm/kvm.h | 2 ++
>> arch/arm64/kvm/handle_exit.c | 24 ++++++++++++----
>> 8 files changed, 141 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/kvm_psci.h b/arch/arm/include/asm/kvm_psci.h
>> index 9a83d98..783566f 100644
>> --- a/arch/arm/include/asm/kvm_psci.h
>> +++ b/arch/arm/include/asm/kvm_psci.h
>> @@ -18,6 +18,29 @@
>> #ifndef __ARM_KVM_PSCI_H__
>> #define __ARM_KVM_PSCI_H__
>>
>> -bool kvm_psci_call(struct kvm_vcpu *vcpu);
>> +#include <linux/kvm_host.h>
>> +#include <asm/kvm_asm.h>
>> +#include <asm/kvm_arm.h>
>> +
>> +/*
>> + * The in-kernel PSCI emulation code wants to use a copy of run->psci,
>> + * which is an anonymous type. Use our own type instead.
>> + */
>> +struct kvm_exit_psci {
>> + u32 fn;
>> + u64 args[7];
>> +};
>> +
>> +static inline void kvm_prepare_psci(struct kvm_run *run,
>> + struct kvm_exit_psci *psci)
>> +{
>> + run->psci.fn = psci->fn;
>> + memcpy(&run->psci.args, &psci->args, sizeof(run->psci.args));
>> + memset(&run->psci.ret, 0, sizeof(run->psci.ret));
>> + run->exit_reason = KVM_EXIT_PSCI;
>> +}
>> +
>> +int kvm_handle_psci_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
>> +int kvm_psci_call(struct kvm_vcpu *vcpu, struct kvm_run *run);
>>
>> #endif /* __ARM_KVM_PSCI_H__ */
>> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
>> index c1ee007..205cf0e 100644
>> --- a/arch/arm/include/uapi/asm/kvm.h
>> +++ b/arch/arm/include/uapi/asm/kvm.h
>> @@ -171,6 +171,8 @@ 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/arm.c b/arch/arm/kvm/arm.c
>> index cc5adb9..5ffd9a3 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -459,7 +459,7 @@ static void update_vttbr(struct kvm *kvm)
>> spin_unlock(&kvm_vmid_lock);
>> }
>>
>> -static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
>> +static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu, struct kvm_run *run)
>
> why this change? run can always be derived from vcpu->run.
Because thats how kvm_handle_mmio_return() and handle_exit() are
implemented.
If you think this is inappropriate then function prototypes for
kvm_handle_mmio_return() and handle_exit() should also change.
IMHO, we should be consistent in usage of vcpu->run.
>
>> {
>> if (likely(vcpu->arch.has_run_once))
>> return 0;
>> @@ -483,7 +483,7 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu)
>> */
>> if (test_and_clear_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features)) {
>> *vcpu_reg(vcpu, 0) = KVM_PSCI_FN_CPU_OFF;
>> - kvm_psci_call(vcpu);
>> + kvm_psci_call(vcpu, run);
>> }
>>
>> return 0;
>> @@ -520,7 +520,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> if (unlikely(!kvm_vcpu_initialized(vcpu)))
>> return -ENOEXEC;
>>
>> - ret = kvm_vcpu_first_run_init(vcpu);
>> + ret = kvm_vcpu_first_run_init(vcpu, vcpu->run);
>> if (ret)
>> return ret;
>>
>> @@ -530,6 +530,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> return ret;
>> }
>>
>> + if (run->exit_reason == KVM_EXIT_PSCI) {
>> + ret = kvm_handle_psci_return(vcpu, vcpu->run);
>> + if (ret)
>> + return ret;
>> + }
>> +
>> if (vcpu->sigset_active)
>> sigprocmask(SIG_SETMASK, &vcpu->sigset, &sigsaved);
>>
>> diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
>> index df4c82d..1a12e6c 100644
>> --- a/arch/arm/kvm/handle_exit.c
>> +++ b/arch/arm/kvm/handle_exit.c
>> @@ -40,14 +40,20 @@ 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, run);
>> + if (!ret)
>> + return 1;
>> + else if (ret == -EINVAL) {
>> + kvm_inject_undefined(vcpu);
>> return 1;
>> + }
>>
>> - kvm_inject_undefined(vcpu);
>> - return 1;
>> + return 0;
>> }
>>
>> 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 86a693a..72c23a7 100644
>> --- a/arch/arm/kvm/psci.c
>> +++ b/arch/arm/kvm/psci.c
>> @@ -71,6 +71,45 @@ 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, struct kvm_run *run)
>> +{
>> + struct kvm_exit_psci psci;
>> +
>> + psci.fn = KVM_PSCI_FN_SYSTEM_OFF;
>> + memset(&psci.args, 0, sizeof(psci.args));
>> + kvm_prepare_psci(run, &psci);
>> +}
>> +
>> +static void kvm_psci_system_reset(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> +{
>> + struct kvm_exit_psci psci;
>> +
>> + psci.fn = KVM_PSCI_FN_SYSTEM_RESET;
>> + memset(&psci.args, 0, sizeof(psci.args));
>> + kvm_prepare_psci(run, &psci);
>> +}
>> +
>> +/**
>> + * kvm_handle_psci_return -- Handle PSCI after user space emulation
>> + * @vcpu: The VCPU pointer
>> + * @run: The VCPU run struct containing the psci data
>> + *
>> + * This should only be called after returning from userspace for
>> + * PSCI emulation.
>> + */
>> +int kvm_handle_psci_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> +{
>> + /*
>> + * Currently, the PSCI functions passed to user space for emulation
>> + * are SYSTEM_OFF and SYSTEM_RESET. These PSCI functions are not
>> + * expected to return back after emulating in user space hence by
>> + * default we return -EINVAL to avoid user space from doing RUN ioctl
>> + * after handling KVM_EXIT_PSCI.
>> + */
>> +
>> + return -EINVAL;
>> +}
>> +
>
> why would reset not return back after emulation?
>
> also, do we need to impose this check or can we get rid of this all
> together, if user space messes up, it's up to user space...
Yes, I think we should allow SYSTEM_RESET to return. I'll update this
with a check.
Actually, when we reach here we also need to update X0-X3 (for ARM R0-R3)
with return values in run->psci. I'll add this in subsequent revision.
>
> Are there any of the other PSCI functions that need specific handling in
> the kernel on the return path?
So far only SYSTEM_RESET and SYSTEM_OFF as per current PSCI spec.
I think people might be also be interested in emulating vendor specific PSCI
calls in user space (QEMU or KVMTOOL or Some proprietary software).
>
>> /**
>> * kvm_psci_call - handle PSCI call if r0 value is in range
>> * @vcpu: Pointer to the VCPU struct
>> @@ -81,8 +120,9 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
>> * function number specified in r0 is withing the PSCI range, and false
>> * otherwise.
>> */
>> -bool kvm_psci_call(struct kvm_vcpu *vcpu)
>> +int kvm_psci_call(struct kvm_vcpu *vcpu, struct kvm_run *run)
>
> why add run here as well?
Please see my previous comments.
--
Anup
>
>> {
>> + int ret = 0;
>> unsigned long psci_fn = *vcpu_reg(vcpu, 0) & ~((u32) 0);
>> unsigned long val;
>>
>> @@ -98,11 +138,20 @@ 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, run);
>> + val = KVM_PSCI_RET_SUCCESS;
>> + ret = -EINTR;
>> + break;
>> + case KVM_PSCI_FN_SYSTEM_RESET:
>> + kvm_psci_system_reset(vcpu, run);
>> + val = KVM_PSCI_RET_SUCCESS;
>> + ret = -EINTR;
>> + 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..db90649 100644
>> --- a/arch/arm64/include/asm/kvm_psci.h
>> +++ b/arch/arm64/include/asm/kvm_psci.h
>> @@ -18,6 +18,29 @@
>> #ifndef __ARM64_KVM_PSCI_H__
>> #define __ARM64_KVM_PSCI_H__
>>
>> -bool kvm_psci_call(struct kvm_vcpu *vcpu);
>> +#include <linux/kvm_host.h>
>> +#include <asm/kvm_asm.h>
>> +#include <asm/kvm_arm.h>
>> +
>> +/*
>> + * The in-kernel PSCI emulation code wants to use a copy of run->psci,
>> + * which is an anonymous type. Use our own type instead.
>> + */
>> +struct kvm_exit_psci {
>> + u32 fn;
>> + u64 args[7];
>> +};
>> +
>> +static inline void kvm_prepare_psci(struct kvm_run *run,
>> + struct kvm_exit_psci *psci)
>> +{
>> + run->psci.fn = psci->fn;
>> + memcpy(&run->psci.args, &psci->args, sizeof(run->psci.args));
>> + memset(&run->psci.ret, 0, sizeof(run->psci.ret));
>> + run->exit_reason = KVM_EXIT_PSCI;
>> +}
>> +
>> +int kvm_handle_psci_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
>> +int kvm_psci_call(struct kvm_vcpu *vcpu, struct kvm_run *run);
>>
>> #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 9beaca0..28e20bb 100644
>> --- a/arch/arm64/kvm/handle_exit.c
>> +++ b/arch/arm64/kvm/handle_exit.c
>> @@ -30,20 +30,32 @@ 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, run);
>> + if (!ret)
>> + return 1;
>> + else if (ret == -EINVAL) {
>> + kvm_inject_undefined(vcpu);
>> return 1;
>> + }
>>
>> - kvm_inject_undefined(vcpu);
>> - return 1;
>> + return 0;
>> }
>>
>> static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> {
>> - if (kvm_psci_call(vcpu))
>> + int ret;
>> +
>> + ret = kvm_psci_call(vcpu, run);
>> + if (!ret)
>> + return 1;
>> + else if (ret == -EINVAL) {
>> + kvm_inject_undefined(vcpu);
>> return 1;
>> + }
>>
>> - kvm_inject_undefined(vcpu);
>> - return 1;
>> + return 0;
>> }
>>
>> /**
>> --
>> 1.7.9.5
>>
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