Re: [Qemu-devel] [PATCH v5] ppc: remove the idle_timer logic

[David Gibson]

On Wed, Jul 24, 2019 at 03:28:28AM -0500, Shivaprasad G Bhat wrote:
> The KVM_CAP_PPC_IRQ_LEVEL is part of the kernel now since 2.6.37.
> Drop the redundant logic which is not excercised on new the kernels anymore.
> 
> Signed-off-by: Shivaprasad G Bhat <address@hidden>

I don't think we want to support such ancient kernels any more, but it
would be good to print a useful error message just in case someoone
does.  So I'd suggest..

> ---
>  v4: https://lists.gnu.org/archive/html/qemu-devel/2019-07/msg04456.html
>  Changes from v4:
>    - it was discussed to drop the idle_timer logic instead of fixing the
>      leak and keeping the redundant logic around. So, the patch does that.
> 
>  target/ppc/kvm.c |   74 
> +-----------------------------------------------------
>  1 file changed, 2 insertions(+), 72 deletions(-)
> 
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 8a06d3171e..1c8f2319a0 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -56,7 +56,6 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
>  };
>  
>  static int cap_interrupt_unset;
> -static int cap_interrupt_level;
>  static int cap_segstate;
>  static int cap_booke_sregs;
>  static int cap_ppc_smt;
> @@ -87,25 +86,6 @@ static int cap_large_decr;
>  
>  static uint32_t debug_inst_opcode;
>  
> -/*
> - * XXX We have a race condition where we actually have a level triggered
> - *     interrupt, but the infrastructure can't expose that yet, so the guest
> - *     takes but ignores it, goes to sleep and never gets notified that 
> there's
> - *     still an interrupt pending.
> - *
> - *     As a quick workaround, let's just wake up again 20 ms after we 
> injected
> - *     an interrupt. That way we can assure that we're always reinjecting
> - *     interrupts in case the guest swallowed them.
> - */
> -static QEMUTimer *idle_timer;
> -
> -static void kvm_kick_cpu(void *opaque)
> -{
> -    PowerPCCPU *cpu = opaque;
> -
> -    qemu_cpu_kick(CPU(cpu));
> -}
> -
>  /*
>   * Check whether we are running with KVM-PR (instead of KVM-HV).  This
>   * should only be used for fallback tests - generally we should use
> @@ -125,7 +105,6 @@ static int kvmppc_get_dec_bits(void);
>  int kvm_arch_init(MachineState *ms, KVMState *s)
>  {
>      cap_interrupt_unset = kvm_check_extension(s, KVM_CAP_PPC_UNSET_IRQ);
> -    cap_interrupt_level = kvm_check_extension(s, KVM_CAP_PPC_IRQ_LEVEL);
>      cap_segstate = kvm_check_extension(s, KVM_CAP_PPC_SEGSTATE);
>      cap_booke_sregs = kvm_check_extension(s, KVM_CAP_PPC_BOOKE_SREGS);
>      cap_ppc_smt_possible = kvm_vm_check_extension(s, 
> KVM_CAP_PPC_SMT_POSSIBLE);
> @@ -161,11 +140,6 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>       */
>      cap_ppc_pvr_compat = false;
>  
> -    if (!cap_interrupt_level) {
> -        fprintf(stderr, "KVM: Couldn't find level irq capability. Expect the 
> "
> -                        "VM to stall at times!\n");
> -    }
> -

..changing this to print such an error and exit(1) if the extension
isn't found.

>      kvm_ppc_register_host_cpu_type(ms);
>  
>      return 0;
> @@ -491,8 +465,6 @@ int kvm_arch_init_vcpu(CPUState *cs)
>          return ret;
>      }
>  
> -    idle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, kvm_kick_cpu, cpu);
> -
>      switch (cenv->mmu_model) {
>      case POWERPC_MMU_BOOKE206:
>          /* This target supports access to KVM's guest TLB */
> @@ -1332,7 +1304,7 @@ int kvmppc_set_interrupt(PowerPCCPU *cpu, int irq, int 
> level)
>          return 0;
>      }
>  
> -    if (!kvm_enabled() || !cap_interrupt_unset || !cap_interrupt_level) {
> +    if (!kvm_enabled() || !cap_interrupt_unset) {
>          return 0;
>      }
>  
> @@ -1349,49 +1321,7 @@ int kvmppc_set_interrupt(PowerPCCPU *cpu, int irq, int 
> level)
>  
>  void kvm_arch_pre_run(CPUState *cs, struct kvm_run *run)
>  {
> -    PowerPCCPU *cpu = POWERPC_CPU(cs);
> -    CPUPPCState *env = &cpu->env;
> -    int r;
> -    unsigned irq;
> -
> -    qemu_mutex_lock_iothread();
> -
> -    /*
> -     * PowerPC QEMU tracks the various core input pins (interrupt,
> -     * critical interrupt, reset, etc) in PPC-specific
> -     * env->irq_input_state.
> -     */
> -    if (!cap_interrupt_level &&
> -        run->ready_for_interrupt_injection &&
> -        (cs->interrupt_request & CPU_INTERRUPT_HARD) &&
> -        (env->irq_input_state & (1 << PPC_INPUT_INT)))
> -    {
> -        /*
> -         * For now KVM disregards the 'irq' argument. However, in the
> -         * future KVM could cache it in-kernel to avoid a heavyweight
> -         * exit when reading the UIC.
> -         */
> -        irq = KVM_INTERRUPT_SET;
> -
> -        trace_kvm_injected_interrupt(irq);
> -        r = kvm_vcpu_ioctl(cs, KVM_INTERRUPT, &irq);
> -        if (r < 0) {
> -            printf("cpu %d fail inject %x\n", cs->cpu_index, irq);
> -        }
> -
> -        /* Always wake up soon in case the interrupt was level based */
> -        timer_mod(idle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
> -                       (NANOSECONDS_PER_SECOND / 50));
> -    }
> -
> -    /*
> -     * We don't know if there are more interrupts pending after
> -     * this. However, the guest will return to userspace in the course
> -     * of handling this one anyways, so we will get a chance to
> -     * deliver the rest.
> -     */
> -
> -    qemu_mutex_unlock_iothread();
> +    return;
>  }
>  
>  MemTxAttrs kvm_arch_post_run(CPUState *cs, struct kvm_run *run)
> 

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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