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    SubjectRe: [PATCH v3 05/10] KVM: arm64: Support stolen time reporting via shared structure
    On Wed, 21 Aug 2019 16:36:51 +0100
    Steven Price <steven.price@arm.com> wrote:

    > Implement the service call for configuring a shared structure between a
    > VCPU and the hypervisor in which the hypervisor can write the time
    > stolen from the VCPU's execution time by other tasks on the host.
    >
    > The hypervisor allocates memory which is placed at an IPA chosen by user
    > space. The hypervisor then updates the shared structure using
    > kvm_put_guest() to ensure single copy atomicity of the 64-bit value
    > reporting the stolen time in nanoseconds.
    >
    > Whenever stolen time is enabled by the guest, the stolen time counter is
    > reset.
    >
    > The stolen time itself is retrieved from the sched_info structure
    > maintained by the Linux scheduler code. We enable SCHEDSTATS when
    > selecting KVM Kconfig to ensure this value is meaningful.
    >
    > Signed-off-by: Steven Price <steven.price@arm.com>

    One totally trivial comment inline... Feel free to ignore :)

    > ---
    > arch/arm/include/asm/kvm_host.h | 20 +++++++++
    > arch/arm64/include/asm/kvm_host.h | 25 +++++++++++-
    > arch/arm64/kvm/Kconfig | 1 +
    > include/linux/kvm_types.h | 2 +
    > virt/kvm/arm/arm.c | 10 +++++
    > virt/kvm/arm/hypercalls.c | 3 ++
    > virt/kvm/arm/pvtime.c | 67 +++++++++++++++++++++++++++++++
    > 7 files changed, 127 insertions(+), 1 deletion(-)
    >
    > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
    > index 369b5d2d54bf..47d2ced99421 100644
    > --- a/arch/arm/include/asm/kvm_host.h
    > +++ b/arch/arm/include/asm/kvm_host.h
    > @@ -39,6 +39,7 @@
    > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
    > #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1)
    > #define KVM_REQ_VCPU_RESET KVM_ARCH_REQ(2)
    > +#define KVM_REQ_RECORD_STEAL KVM_ARCH_REQ(3)
    >
    > DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
    >
    > @@ -329,6 +330,25 @@ static inline int kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
    > return SMCCC_RET_NOT_SUPPORTED;
    > }
    >
    > +static inline int kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu)
    > +{
    > + return SMCCC_RET_NOT_SUPPORTED;
    > +}
    > +
    > +static inline int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
    > +{
    > + return -ENOTSUPP;
    > +}
    > +
    > +static inline void kvm_pvtime_init_vm(struct kvm_arch *kvm_arch)
    > +{
    > +}
    > +
    > +static inline bool kvm_is_pvtime_enabled(struct kvm_arch *kvm_arch)
    > +{
    > + return false;
    > +}
    > +
    > void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
    >
    > struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
    > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
    > index 583b3639062a..b6fa7beffd8a 100644
    > --- a/arch/arm64/include/asm/kvm_host.h
    > +++ b/arch/arm64/include/asm/kvm_host.h
    > @@ -44,6 +44,7 @@
    > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
    > #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1)
    > #define KVM_REQ_VCPU_RESET KVM_ARCH_REQ(2)
    > +#define KVM_REQ_RECORD_STEAL KVM_ARCH_REQ(3)
    >
    > DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
    >
    > @@ -83,6 +84,11 @@ struct kvm_arch {
    >
    > /* Mandated version of PSCI */
    > u32 psci_version;
    > +
    > + struct kvm_arch_pvtime {
    > + gpa_t st_base;
    > + u64 st_size;
    > + } pvtime;
    > };
    >
    > #define KVM_NR_MEM_OBJS 40
    > @@ -338,8 +344,13 @@ struct kvm_vcpu_arch {
    > /* True when deferrable sysregs are loaded on the physical CPU,
    > * see kvm_vcpu_load_sysregs and kvm_vcpu_put_sysregs. */
    > bool sysregs_loaded_on_cpu;
    > -};
    >
    > + /* Guest PV state */
    > + struct {
    > + u64 steal;
    > + u64 last_steal;
    > + } steal;
    > +};
    > /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
    > #define vcpu_sve_pffr(vcpu) ((void *)((char *)((vcpu)->arch.sve_state) + \
    > sve_ffr_offset((vcpu)->arch.sve_max_vl)))
    > @@ -479,6 +490,18 @@ int kvm_perf_init(void);
    > int kvm_perf_teardown(void);
    >
    > int kvm_hypercall_pv_features(struct kvm_vcpu *vcpu);
    > +int kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu);
    > +int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init);
    > +
    > +static inline void kvm_pvtime_init_vm(struct kvm_arch *kvm_arch)
    > +{
    > + kvm_arch->pvtime.st_base = GPA_INVALID;
    > +}
    > +
    > +static inline bool kvm_is_pvtime_enabled(struct kvm_arch *kvm_arch)
    > +{
    > + return (kvm_arch->pvtime.st_base != GPA_INVALID);
    > +}
    >
    > void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
    >
    > diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
    > index a67121d419a2..d8b88e40d223 100644
    > --- a/arch/arm64/kvm/Kconfig
    > +++ b/arch/arm64/kvm/Kconfig
    > @@ -39,6 +39,7 @@ config KVM
    > select IRQ_BYPASS_MANAGER
    > select HAVE_KVM_IRQ_BYPASS
    > select HAVE_KVM_VCPU_RUN_PID_CHANGE
    > + select SCHEDSTATS
    > ---help---
    > Support hosting virtualized guest machines.
    > We don't support KVM with 16K page tables yet, due to the multiple
    > diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
    > index bde5374ae021..1c88e69db3d9 100644
    > --- a/include/linux/kvm_types.h
    > +++ b/include/linux/kvm_types.h
    > @@ -35,6 +35,8 @@ typedef unsigned long gva_t;
    > typedef u64 gpa_t;
    > typedef u64 gfn_t;
    >
    > +#define GPA_INVALID (~(gpa_t)0)
    > +
    > typedef unsigned long hva_t;
    > typedef u64 hpa_t;
    > typedef u64 hfn_t;
    > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
    > index 35a069815baf..5e8343e2dd62 100644
    > --- a/virt/kvm/arm/arm.c
    > +++ b/virt/kvm/arm/arm.c
    > @@ -40,6 +40,10 @@
    > #include <asm/kvm_coproc.h>
    > #include <asm/sections.h>
    >
    > +#include <kvm/arm_hypercalls.h>
    > +#include <kvm/arm_pmu.h>
    > +#include <kvm/arm_psci.h>
    > +
    > #ifdef REQUIRES_VIRT
    > __asm__(".arch_extension virt");
    > #endif
    > @@ -135,6 +139,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
    > kvm->arch.max_vcpus = vgic_present ?
    > kvm_vgic_get_max_vcpus() : KVM_MAX_VCPUS;
    >
    > + kvm_pvtime_init_vm(&kvm->arch);
    > return ret;
    > out_free_stage2_pgd:
    > kvm_free_stage2_pgd(kvm);
    > @@ -379,6 +384,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
    > kvm_vcpu_load_sysregs(vcpu);
    > kvm_arch_vcpu_load_fp(vcpu);
    > kvm_vcpu_pmu_restore_guest(vcpu);
    > + if (kvm_is_pvtime_enabled(&vcpu->kvm->arch))
    > + kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu);
    >
    > if (single_task_running())
    > vcpu_clear_wfe_traps(vcpu);
    > @@ -644,6 +651,9 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
    > * that a VCPU sees new virtual interrupts.
    > */
    > kvm_check_request(KVM_REQ_IRQ_PENDING, vcpu);
    > +
    > + if (kvm_check_request(KVM_REQ_RECORD_STEAL, vcpu))
    > + kvm_update_stolen_time(vcpu, false);
    > }
    > }
    >
    > diff --git a/virt/kvm/arm/hypercalls.c b/virt/kvm/arm/hypercalls.c
    > index 63ae629c466a..ac678eabf15f 100644
    > --- a/virt/kvm/arm/hypercalls.c
    > +++ b/virt/kvm/arm/hypercalls.c
    > @@ -56,6 +56,9 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
    > case ARM_SMCCC_HV_PV_FEATURES:
    > val = kvm_hypercall_pv_features(vcpu);
    > break;
    > + case ARM_SMCCC_HV_PV_TIME_ST:
    > + val = kvm_hypercall_stolen_time(vcpu);
    > + break;
    > default:
    > return kvm_psci_call(vcpu);
    > }
    > diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
    > index 6201d71cb1f8..28603689f6e0 100644
    > --- a/virt/kvm/arm/pvtime.c
    > +++ b/virt/kvm/arm/pvtime.c
    > @@ -3,8 +3,51 @@
    >
    > #include <linux/arm-smccc.h>
    >
    > +#include <asm/pvclock-abi.h>
    > +
    > #include <kvm/arm_hypercalls.h>
    >
    > +int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
    > +{
    > + struct kvm *kvm = vcpu->kvm;
    > + struct kvm_arch_pvtime *pvtime = &kvm->arch.pvtime;
    > + u64 steal;
    > + u64 steal_le;
    > + u64 offset;
    > + int idx;
    > + const int stride = sizeof(struct pvclock_vcpu_stolen_time);
    > +
    > + if (pvtime->st_base == GPA_INVALID)
    > + return -ENOTSUPP;
    > +
    > + /* Let's do the local bookkeeping */
    > + steal = vcpu->arch.steal.steal;
    > + steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
    > + vcpu->arch.steal.last_steal = current->sched_info.run_delay;
    > + vcpu->arch.steal.steal = steal;
    > +
    > + offset = stride * kvm_vcpu_get_idx(vcpu);
    > +
    > + if (unlikely(offset + stride > pvtime->st_size))
    > + return -EINVAL;
    > +
    > + steal_le = cpu_to_le64(steal);
    > + idx = srcu_read_lock(&kvm->srcu);
    > + if (init) {
    > + struct pvclock_vcpu_stolen_time init_values = {
    > + .revision = 0,
    > + .attributes = 0
    > + };
    > + kvm_write_guest(kvm, pvtime->st_base + offset, &init_values,
    > + sizeof(init_values));
    > + }
    > + offset += offsetof(struct pvclock_vcpu_stolen_time, stolen_time);
    > + kvm_put_guest(kvm, pvtime->st_base + offset, steal_le, u64);
    > + srcu_read_unlock(&kvm->srcu, idx);
    > +
    > + return 0;
    > +}
    > +
    > int kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
    > {
    > u32 feature = smccc_get_arg1(vcpu);
    > @@ -12,6 +55,7 @@ int kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
    >
    > switch (feature) {
    > case ARM_SMCCC_HV_PV_FEATURES:
    > + case ARM_SMCCC_HV_PV_TIME_ST:
    > val = SMCCC_RET_SUCCESS;
    > break;
    > }
    > @@ -19,3 +63,26 @@ int kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
    > return val;
    > }
    >
    > +int kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu)
    > +{
    > + u64 ret;
    > + int err;
    > +
    > + /*
    > + * Start counting stolen time from the time the guest requests
    > + * the feature enabled.
    > + */
    > + vcpu->arch.steal.steal = 0;
    > + vcpu->arch.steal.last_steal = current->sched_info.run_delay;
    > +
    > + err = kvm_update_stolen_time(vcpu, true);
    > +
    > + if (err)
    > + ret = SMCCC_RET_NOT_SUPPORTED;

    Trivial by why not
    return SMCCC_RET_NOT_SUPPORTED;

    return vcpu->kvm->arch.pvtime.st_base +
    ...
    Drops the indentation a bit and puts the error handling out of
    line which is slightly nicer to read (to my eyes).

    > + else
    > + ret = vcpu->kvm->arch.pvtime.st_base +
    > + (sizeof(struct pvclock_vcpu_stolen_time) *
    > + kvm_vcpu_get_idx(vcpu));
    > +
    > + return ret;
    > +}


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