Having a per-vcpu virtual offset is a pain. It needs to be synchronized on each update, and expands badly to a setup where different timers can have different offsets, or have composite offsets (as with NV). So let's start by replacing the use of the CNTVOFF_EL2 shadow register (which we want to reclaim for NV anyway), and make the virtual timer carry a pointer to a VM-wide offset. This simplifies the code significantly. It also addresses two terrible bugs: - The use of CNTVOFF_EL2 leads to some nice offset corruption when the sysreg gets reset, as reported by Joey. - The kvm mutex is taken from a vcpu ioctl, which goes against the locking rules... Reported-by: Joey Gouly <joey.gouly@xxxxxxx> Reviewed-by: Reiji Watanabe <reijiw@xxxxxxxxxx> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> Link: https://lore.kernel.org/r/20230224173915.GA17407@xxxxxxxxxxxxxxxxxxxxxxxxx --- arch/arm64/include/asm/kvm_host.h | 3 +++ arch/arm64/kvm/arch_timer.c | 45 +++++++------------------------ arch/arm64/kvm/hypercalls.c | 2 +- include/kvm/arm_arch_timer.h | 15 +++++++++++ 4 files changed, 29 insertions(+), 36 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index a1892a8f6032..bcd774d74f34 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -193,6 +193,9 @@ struct kvm_arch { /* Interrupt controller */ struct vgic_dist vgic; + /* Timers */ + struct arch_timer_vm_data timer_data; + /* Mandated version of PSCI */ u32 psci_version; diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c index 00610477ec7b..e1af4301b913 100644 --- a/arch/arm64/kvm/arch_timer.c +++ b/arch/arm64/kvm/arch_timer.c @@ -84,14 +84,10 @@ 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; + if (ctxt->offset.vm_offset) + return *ctxt->offset.vm_offset; - switch(arch_timer_ctx_index(ctxt)) { - case TIMER_VTIMER: - return __vcpu_sys_reg(vcpu, CNTVOFF_EL2); - default: - return 0; - } + return 0; } static void timer_set_ctl(struct arch_timer_context *ctxt, u32 ctl) @@ -128,15 +124,12 @@ static void timer_set_cval(struct arch_timer_context *ctxt, u64 cval) static void timer_set_offset(struct arch_timer_context *ctxt, u64 offset) { - struct kvm_vcpu *vcpu = ctxt->vcpu; - - switch(arch_timer_ctx_index(ctxt)) { - case TIMER_VTIMER: - __vcpu_sys_reg(vcpu, CNTVOFF_EL2) = offset; - break; - default: + if (!ctxt->offset.vm_offset) { WARN(offset, "timer %ld\n", arch_timer_ctx_index(ctxt)); + return; } + + WRITE_ONCE(*ctxt->offset.vm_offset, offset); } u64 kvm_phys_timer_read(void) @@ -765,25 +758,6 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu) return 0; } -/* Make the updates of cntvoff for all vtimer contexts atomic */ -static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff) -{ - unsigned long i; - struct kvm *kvm = vcpu->kvm; - struct kvm_vcpu *tmp; - - mutex_lock(&kvm->lock); - kvm_for_each_vcpu(i, tmp, kvm) - timer_set_offset(vcpu_vtimer(tmp), cntvoff); - - /* - * When called from the vcpu create path, the CPU being created is not - * included in the loop above, so we just set it here as well. - */ - timer_set_offset(vcpu_vtimer(vcpu), cntvoff); - mutex_unlock(&kvm->lock); -} - void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu) { struct arch_timer_cpu *timer = vcpu_timer(vcpu); @@ -791,10 +765,11 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu) struct arch_timer_context *ptimer = vcpu_ptimer(vcpu); vtimer->vcpu = vcpu; + vtimer->offset.vm_offset = &vcpu->kvm->arch.timer_data.voffset; ptimer->vcpu = vcpu; /* Synchronize cntvoff across all vtimers of a VM. */ - update_vtimer_cntvoff(vcpu, kvm_phys_timer_read()); + timer_set_offset(vtimer, kvm_phys_timer_read()); timer_set_offset(ptimer, 0); hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD); @@ -840,7 +815,7 @@ int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value) break; case KVM_REG_ARM_TIMER_CNT: timer = vcpu_vtimer(vcpu); - update_vtimer_cntvoff(vcpu, kvm_phys_timer_read() - value); + timer_set_offset(timer, kvm_phys_timer_read() - value); break; case KVM_REG_ARM_TIMER_CVAL: timer = vcpu_vtimer(vcpu); diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c index 64c086c02c60..5da884e11337 100644 --- a/arch/arm64/kvm/hypercalls.c +++ b/arch/arm64/kvm/hypercalls.c @@ -44,7 +44,7 @@ static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val) feature = smccc_get_arg1(vcpu); switch (feature) { case KVM_PTP_VIRT_COUNTER: - cycles = systime_snapshot.cycles - vcpu_read_sys_reg(vcpu, CNTVOFF_EL2); + cycles = systime_snapshot.cycles - vcpu->kvm->arch.timer_data.voffset; break; case KVM_PTP_PHYS_COUNTER: cycles = systime_snapshot.cycles; diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h index 71916de7c6c4..c52a6e6839da 100644 --- a/include/kvm/arm_arch_timer.h +++ b/include/kvm/arm_arch_timer.h @@ -23,6 +23,19 @@ enum kvm_arch_timer_regs { TIMER_REG_CTL, }; +struct arch_timer_offset { + /* + * If set, pointer to one of the offsets in the kvm's offset + * structure. If NULL, assume a zero offset. + */ + u64 *vm_offset; +}; + +struct arch_timer_vm_data { + /* Offset applied to the virtual timer/counter */ + u64 voffset; +}; + struct arch_timer_context { struct kvm_vcpu *vcpu; @@ -32,6 +45,8 @@ struct arch_timer_context { /* Emulated Timer (may be unused) */ struct hrtimer hrtimer; + /* Offset for this counter/timer */ + struct arch_timer_offset offset; /* * We have multiple paths which can save/restore the timer state onto * the hardware, so we need some way of keeping track of where the -- 2.34.1
