On Wed, Aug 04, 2021 at 08:58:15AM +0000, Oliver Upton wrote:
> Presently, KVM provides no facilities for correctly migrating a guest
> that depends on the physical counter-timer. Whie most guests (barring
> NV, of course) should not depend on the physical counter-timer, an
> operator may wish to provide a consistent view of the physical
> counter-timer across migrations.
>
> Provide userspace with a new vCPU attribute to modify the guest
> counter-timer offset. Unlike KVM_REG_ARM_TIMER_OFFSET, this attribute is
> hidden from the guest's architectural state. The value offsets *both*
> the virtual and physical counter-timer views for the guest. Only support
> this attribute on ECV systems as ECV is required for hardware offsetting
> of the physical counter-timer.
>
> Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
> ---
> Documentation/virt/kvm/devices/vcpu.rst | 28 ++++++
> arch/arm64/include/asm/kvm_asm.h | 2 +
> arch/arm64/include/asm/sysreg.h | 2 +
> arch/arm64/include/uapi/asm/kvm.h | 1 +
> arch/arm64/kvm/arch_timer.c | 122 +++++++++++++++++++++++-
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 6 ++
> arch/arm64/kvm/hyp/nvhe/timer-sr.c | 5 +
> arch/arm64/kvm/hyp/vhe/timer-sr.c | 5 +
> include/clocksource/arm_arch_timer.h | 1 +
> 9 files changed, 169 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst
> index 3b399d727c11..3ba35b9d9d03 100644
> --- a/Documentation/virt/kvm/devices/vcpu.rst
> +++ b/Documentation/virt/kvm/devices/vcpu.rst
> @@ -139,6 +139,34 @@ configured values on other VCPUs. Userspace should configure the interrupt
> numbers on at least one VCPU after creating all VCPUs and before running any
> VCPUs.
>
> +2.2. ATTRIBUTE: KVM_ARM_VCPU_TIMER_OFFSET
> +-----------------------------------------
> +
> +:Parameters: in kvm_device_attr.addr the address for the timer offset is a
> + pointer to a __u64
> +
> +Returns:
> +
> + ======= ==================================
> + -EFAULT Error reading/writing the provided
> + parameter address
> + -ENXIO Timer offsetting not implemented
> + ======= ==================================
> +
> +Specifies the guest's counter-timer offset from the host's virtual counter.
> +The guest's physical counter value is then derived by the following
> +equation:
> +
> + guest_cntpct = host_cntvct - KVM_ARM_VCPU_TIMER_OFFSET
> +
> +The guest's virtual counter value is derived by the following equation:
> +
> + guest_cntvct = host_cntvct - KVM_REG_ARM_TIMER_OFFSET
> + - KVM_ARM_VCPU_TIMER_OFFSET
> +
> +KVM does not allow the use of varying offset values for different vCPUs;
> +the last written offset value will be broadcasted to all vCPUs in a VM.
> +
> 3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL
> ==================================
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 9f0bf2109be7..ab1c8fdb0177 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -65,6 +65,7 @@
> #define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19
> #define __KVM_HOST_SMCCC_FUNC___pkvm_mark_hyp 20
> #define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc 21
> +#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntpoff 22
>
> #ifndef __ASSEMBLY__
>
> @@ -200,6 +201,7 @@ extern void __kvm_tlb_flush_vmid_ipa(struct kvm_s2_mmu *mmu, phys_addr_t ipa,
> extern void __kvm_tlb_flush_vmid(struct kvm_s2_mmu *mmu);
>
> extern void __kvm_timer_set_cntvoff(u64 cntvoff);
> +extern void __kvm_timer_set_cntpoff(u64 cntpoff);
>
> extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
>
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 4dfc44066dfb..c34672aa65b9 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -586,6 +586,8 @@
> #define SYS_ICH_LR14_EL2 __SYS__LR8_EL2(6)
> #define SYS_ICH_LR15_EL2 __SYS__LR8_EL2(7)
>
> +#define SYS_CNTPOFF_EL2 sys_reg(3, 4, 14, 0, 6)
> +
> /* VHE encodings for architectural EL0/1 system registers */
> #define SYS_SCTLR_EL12 sys_reg(3, 5, 1, 0, 0)
> #define SYS_CPACR_EL12 sys_reg(3, 5, 1, 0, 2)
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 949a31bc10f0..15150f8224a1 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -366,6 +366,7 @@ struct kvm_arm_copy_mte_tags {
> #define KVM_ARM_VCPU_TIMER_CTRL 1
> #define KVM_ARM_VCPU_TIMER_IRQ_VTIMER 0
> #define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1
> +#define KVM_ARM_VCPU_TIMER_OFFSET 2
> #define KVM_ARM_VCPU_PVTIME_CTRL 2
> #define KVM_ARM_VCPU_PVTIME_IPA 0
>
> diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
> index a8815b09da3e..f15058612994 100644
> --- a/arch/arm64/kvm/arch_timer.c
> +++ b/arch/arm64/kvm/arch_timer.c
> @@ -85,11 +85,15 @@ u64 timer_get_cval(struct arch_timer_context *ctxt)
> static u64 timer_get_offset(struct arch_timer_context *ctxt)
> {
> struct kvm_vcpu *vcpu = ctxt->vcpu;
> + struct arch_timer_cpu *timer = vcpu_timer(vcpu);
This new timer variable doesn't appear to get used.
>
> switch(arch_timer_ctx_index(ctxt)) {
> case TIMER_VTIMER:
> + case TIMER_PTIMER:
> return ctxt->host_offset;
> default:
> + WARN_ONCE(1, "unrecognized timer %ld\n",
> + arch_timer_ctx_index(ctxt));
> return 0;
> }
> }
> @@ -144,6 +148,7 @@ static void timer_set_offset(struct arch_timer_context *ctxt, u64 offset)
>
> switch(arch_timer_ctx_index(ctxt)) {
> case TIMER_VTIMER:
> + case TIMER_PTIMER:
> ctxt->host_offset = offset;
> break;
> default:
> @@ -572,6 +577,11 @@ static void set_cntvoff(u64 cntvoff)
> kvm_call_hyp(__kvm_timer_set_cntvoff, cntvoff);
> }
>
> +static void set_cntpoff(u64 cntpoff)
> +{
> + kvm_call_hyp(__kvm_timer_set_cntpoff, cntpoff);
> +}
> +
> static inline void set_timer_irq_phys_active(struct arch_timer_context *ctx, bool active)
> {
> int r;
> @@ -647,6 +657,8 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
> }
>
> set_cntvoff(timer_get_offset(map.direct_vtimer));
> + if (cpus_have_const_cap(ARM64_ECV))
> + set_cntpoff(timer_get_offset(vcpu_ptimer(vcpu)));
>
> kvm_timer_unblocking(vcpu);
>
> @@ -814,6 +826,22 @@ static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
> mutex_unlock(&kvm->lock);
> }
>
> +static void update_ptimer_cntpoff(struct kvm_vcpu *vcpu, u64 cntpoff)
> +{
> + struct kvm *kvm = vcpu->kvm;
> + u64 cntvoff;
> +
> + mutex_lock(&kvm->lock);
> +
> + /* adjustments to the physical offset also affect vtimer */
> + cntvoff = timer_get_offset(vcpu_vtimer(vcpu));
> + cntvoff += cntpoff - timer_get_offset(vcpu_ptimer(vcpu));
> +
> + update_timer_offset(vcpu, TIMER_PTIMER, cntpoff, false);
> + update_timer_offset(vcpu, TIMER_VTIMER, cntvoff, false);
> + mutex_unlock(&kvm->lock);
> +}
> +
> void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
> {
> struct arch_timer_cpu *timer = vcpu_timer(vcpu);
> @@ -932,6 +960,29 @@ u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
> return (u64)-1;
> }
>
> +/**
> + * kvm_arm_timer_read_offset - returns the guest value of CNTVOFF_EL2.
> + * @vcpu: the vcpu pointer
> + *
> + * Computes the guest value of CNTVOFF_EL2 by subtracting the physical
> + * counter offset. Note that KVM defines CNTVOFF_EL2 as the offset from the
> + * guest's physical counter-timer, not the host's.
> + *
> + * Returns: the guest value for CNTVOFF_EL2
> + */
> +static u64 kvm_arm_timer_read_offset(struct kvm_vcpu *vcpu)
> +{
> + struct kvm *kvm = vcpu->kvm;
> + u64 offset;
> +
> + mutex_lock(&kvm->lock);
> + offset = timer_get_offset(vcpu_vtimer(vcpu)) -
> + timer_get_offset(vcpu_ptimer(vcpu));
> + mutex_unlock(&kvm->lock);
> +
> + return offset;
> +}
> +
> static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu,
> struct arch_timer_context *timer,
> enum kvm_arch_timer_regs treg)
> @@ -957,7 +1008,7 @@ static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu,
> break;
>
> case TIMER_REG_OFFSET:
> - val = timer_get_offset(timer);
> + val = kvm_arm_timer_read_offset(vcpu);
> break;
>
> default:
> @@ -1350,6 +1401,9 @@ void kvm_timer_init_vhe(void)
> val = read_sysreg(cnthctl_el2);
> val |= (CNTHCTL_EL1PCEN << cnthctl_shift);
> val |= (CNTHCTL_EL1PCTEN << cnthctl_shift);
> +
> + if (cpus_have_const_cap(ARM64_ECV))
> + val |= CNTHCTL_ECV;
> write_sysreg(val, cnthctl_el2);
> }
>
> @@ -1364,7 +1418,8 @@ static void set_timer_irqs(struct kvm *kvm, int vtimer_irq, int ptimer_irq)
> }
> }
>
> -int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> +static int kvm_arm_timer_set_attr_irq(struct kvm_vcpu *vcpu,
> + struct kvm_device_attr *attr)
> {
> int __user *uaddr = (int __user *)(long)attr->addr;
> struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
> @@ -1397,7 +1452,37 @@ int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> return 0;
> }
>
> -int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> +static int kvm_arm_timer_set_attr_offset(struct kvm_vcpu *vcpu,
> + struct kvm_device_attr *attr)
> +{
> + u64 __user *uaddr = (u64 __user *)(long)attr->addr;
> + u64 offset;
> +
> + if (!cpus_have_const_cap(ARM64_ECV))
> + return -ENXIO;
> +
> + if (get_user(offset, uaddr))
> + return -EFAULT;
> +
> + update_ptimer_cntpoff(vcpu, offset);
> + return 0;
> +}
> +
> +int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> +{
> + switch (attr->attr) {
> + case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
> + case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
> + return kvm_arm_timer_set_attr_irq(vcpu, attr);
> + case KVM_ARM_VCPU_TIMER_OFFSET:
> + return kvm_arm_timer_set_attr_offset(vcpu, attr);
> + default:
> + return -ENXIO;
> + }
> +}
> +
> +static int kvm_arm_timer_get_attr_irq(struct kvm_vcpu *vcpu,
> + struct kvm_device_attr *attr)
> {
> int __user *uaddr = (int __user *)(long)attr->addr;
> struct arch_timer_context *timer;
> @@ -1418,12 +1503,43 @@ int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> return put_user(irq, uaddr);
> }
>
> +static int kvm_arm_timer_get_attr_offset(struct kvm_vcpu *vcpu,
> + struct kvm_device_attr *attr)
> +{
> + u64 __user *uaddr = (u64 __user *)(long)attr->addr;
> + u64 offset;
> +
> + if (!cpus_have_const_cap(ARM64_ECV))
> + return -ENXIO;
> +
> + offset = timer_get_offset(vcpu_ptimer(vcpu));
> + return put_user(offset, uaddr);
> +}
> +
> +int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu,
> + struct kvm_device_attr *attr)
> +{
> + switch (attr->attr) {
> + case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
> + case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
> + return kvm_arm_timer_get_attr_irq(vcpu, attr);
> + case KVM_ARM_VCPU_TIMER_OFFSET:
> + return kvm_arm_timer_get_attr_offset(vcpu, attr);
> + default:
> + return -ENXIO;
> + }
> +}
> +
> int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
> {
> switch (attr->attr) {
> case KVM_ARM_VCPU_TIMER_IRQ_VTIMER:
> case KVM_ARM_VCPU_TIMER_IRQ_PTIMER:
> return 0;
> + case KVM_ARM_VCPU_TIMER_OFFSET:
> + if (cpus_have_const_cap(ARM64_ECV))
> + return 0;
> + break;
> }
>
> return -ENXIO;
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index 1632f001f4ed..cfa923df3af6 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -68,6 +68,11 @@ static void handle___kvm_timer_set_cntvoff(struct kvm_cpu_context *host_ctxt)
> __kvm_timer_set_cntvoff(cpu_reg(host_ctxt, 1));
> }
>
> +static void handle___kvm_timer_set_cntpoff(struct kvm_cpu_context *host_ctxt)
> +{
> + __kvm_timer_set_cntpoff(cpu_reg(host_ctxt, 1));
> +}
> +
> static void handle___kvm_enable_ssbs(struct kvm_cpu_context *host_ctxt)
> {
> u64 tmp;
> @@ -197,6 +202,7 @@ static const hcall_t host_hcall[] = {
> HANDLE_FUNC(__pkvm_create_private_mapping),
> HANDLE_FUNC(__pkvm_prot_finalize),
> HANDLE_FUNC(__pkvm_mark_hyp),
> + HANDLE_FUNC(__kvm_timer_set_cntpoff),
> };
>
> static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
> diff --git a/arch/arm64/kvm/hyp/nvhe/timer-sr.c b/arch/arm64/kvm/hyp/nvhe/timer-sr.c
> index 9072e71693ba..5b8b4cd02506 100644
> --- a/arch/arm64/kvm/hyp/nvhe/timer-sr.c
> +++ b/arch/arm64/kvm/hyp/nvhe/timer-sr.c
> @@ -15,6 +15,11 @@ void __kvm_timer_set_cntvoff(u64 cntvoff)
> write_sysreg(cntvoff, cntvoff_el2);
> }
>
> +void __kvm_timer_set_cntpoff(u64 cntpoff)
> +{
> + write_sysreg_s(cntpoff, SYS_CNTPOFF_EL2);
> +}
> +
> /*
> * Should only be called on non-VHE systems.
> * VHE systems use EL2 timers and configure EL1 timers in kvm_timer_init_vhe().
> diff --git a/arch/arm64/kvm/hyp/vhe/timer-sr.c b/arch/arm64/kvm/hyp/vhe/timer-sr.c
> index 4cda674a8be6..231e16a071a5 100644
> --- a/arch/arm64/kvm/hyp/vhe/timer-sr.c
> +++ b/arch/arm64/kvm/hyp/vhe/timer-sr.c
> @@ -10,3 +10,8 @@ void __kvm_timer_set_cntvoff(u64 cntvoff)
> {
> write_sysreg(cntvoff, cntvoff_el2);
> }
> +
> +void __kvm_timer_set_cntpoff(u64 cntpoff)
> +{
> + write_sysreg_s(cntpoff, SYS_CNTPOFF_EL2);
> +}
> diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
> index 73c7139c866f..7252ffa3d675 100644
> --- a/include/clocksource/arm_arch_timer.h
> +++ b/include/clocksource/arm_arch_timer.h
> @@ -21,6 +21,7 @@
> #define CNTHCTL_EVNTEN (1 << 2)
> #define CNTHCTL_EVNTDIR (1 << 3)
> #define CNTHCTL_EVNTI (0xF << 4)
> +#define CNTHCTL_ECV (1 << 12)
>
> enum arch_timer_reg {
> ARCH_TIMER_REG_CTRL,
> --
> 2.32.0.605.g8dce9f2422-goog
>
Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
