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Re: [Qemu-devel] [PATCH v4] ppc: make idle_timer a per-cpu variable
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH v4] ppc: make idle_timer a per-cpu variable |
Date: |
Mon, 22 Jul 2019 18:44:24 +1000 |
User-agent: |
Mutt/1.12.0 (2019-05-25) |
On Fri, Jul 19, 2019 at 03:51:26AM -0500, Shivaprasad G Bhat wrote:
> The current code is broken for more than vcpu as
> each thread would overwrite idle_timer and there were
> memory leaks.
>
> Make it part of PowerPCCPU so that every thread has a
> separate one. Avoid using the timer_new_ns which is
> not the preferred way to create timers.
>
> Signed-off-by: Shivaprasad G Bhat <address@hidden>
> Reviewed-by: Greg Kurz <address@hidden>
So, this looks correct, but..
..the whole idle_timer logic is used only in the case that we're
running with a KVM that doesn't support KVM_CAP_PPC_IRQ_LEVEL. That
support appears to have been in since around v2.6.36 some 9 years
ago. We could probably just drop support for such old kernels in qemu
instead.
> ---
> v3: https://lists.gnu.org/archive/html/qemu-devel/2019-07/msg04375.html
> Changes from v3:
> - Calling timer_del() before timer_deinit()
>
> target/ppc/cpu.h | 1 +
> target/ppc/kvm.c | 32 +++++++++++++++++---------------
> 2 files changed, 18 insertions(+), 15 deletions(-)
>
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index c9beba2a5c..521086d91a 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -1190,6 +1190,7 @@ struct PowerPCCPU {
> void *machine_data;
> int32_t node_id; /* NUMA node this CPU belongs to */
> PPCHash64Options *hash64_opts;
> + QEMUTimer idle_timer;
>
> /* Fields related to migration compatibility hacks */
> bool pre_2_8_migration;
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 8a06d3171e..52d3292f45 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -87,18 +87,6 @@ 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;
> @@ -491,7 +479,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
> return ret;
> }
>
> - idle_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, kvm_kick_cpu, cpu);
> + timer_init_ns(&cpu->idle_timer, QEMU_CLOCK_VIRTUAL, kvm_kick_cpu, cpu);
>
> switch (cenv->mmu_model) {
> case POWERPC_MMU_BOOKE206:
> @@ -523,6 +511,11 @@ int kvm_arch_init_vcpu(CPUState *cs)
>
> int kvm_arch_destroy_vcpu(CPUState *cs)
> {
> + PowerPCCPU *cpu = POWERPC_CPU(cs);
> +
> + timer_del(&cpu->idle_timer);
> + timer_deinit(&cpu->idle_timer);
> +
> return 0;
> }
>
> @@ -1379,8 +1372,17 @@ void kvm_arch_pre_run(CPUState *cs, struct kvm_run
> *run)
> 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) +
> + /*
> + * 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.
> + */
> + timer_mod(&cpu->idle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
> (NANOSECONDS_PER_SECOND / 50));
> }
>
>
--
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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