From: Chenyi Qiang <chenyi.qiang@intel.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, Xiaoyao Li <xiaoyao.li@intel.com>
Subject: Re: [PATCH v4] i386: Add ratelimit for bus locks acquired in guest
Date: Mon, 31 May 2021 13:14:54 +0800 [thread overview]
Message-ID: <e9b152b8-daad-aaa4-c89d-35fd839f2ae4@intel.com> (raw)
In-Reply-To: <20210527211904.sjmkely4t4ragxva@habkost.net>
On 5/28/2021 5:19 AM, Eduardo Habkost wrote:
> On Fri, May 21, 2021 at 12:38:20PM +0800, Chenyi Qiang wrote:
> [...]
>> @@ -4222,6 +4247,15 @@ void kvm_arch_pre_run(CPUState *cpu, struct kvm_run *run)
>> }
>> }
>>
>> +static void kvm_rate_limit_on_bus_lock(void)
>> +{
>> + uint64_t delay_ns = ratelimit_calculate_delay(&bus_lock_ratelimit_ctrl, 1);
>> +
>> + if (delay_ns) {
>> + g_usleep(delay_ns / SCALE_US);
>> + }
>> +}
>> +
>> MemTxAttrs kvm_arch_post_run(CPUState *cpu, struct kvm_run *run)
>> {
>> X86CPU *x86_cpu = X86_CPU(cpu);
>> @@ -4237,6 +4271,9 @@ MemTxAttrs kvm_arch_post_run(CPUState *cpu, struct kvm_run *run)
>> } else {
>> env->eflags &= ~IF_MASK;
>> }
>> + if (run->flags & KVM_RUN_X86_BUS_LOCK) {
>
> Does the KVM API guarantee that KVM_RUN_X86_BUS_LOCK will never
> be set if KVM_BUS_LOCK_DETECTION_EXIT isn't enabled? (Otherwise
> we risk crashing in ratelimit_calculate_delay() above if rate
> limiting is disabled).
>
Yes. KVM_RUN_X86_BUS_LOCK flag is set when bus lock VM exit happens. Bus
lock VM exit is disabled by default and can only be enabled through the
KVM_BUS_LOCK_DETECTION_EXIT capability.
> If that's guaranteed, the patch looks good to me now.
>
>> + kvm_rate_limit_on_bus_lock();
>> + }
>>
>> /* We need to protect the apic state against concurrent accesses from
>> * different threads in case the userspace irqchip is used. */
>> @@ -4595,6 +4632,10 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
>> ioapic_eoi_broadcast(run->eoi.vector);
>> ret = 0;
>> break;
>> + case KVM_EXIT_X86_BUS_LOCK:
>> + /* already handled in kvm_arch_post_run */
>> + ret = 0;
>> + break;
>> default:
>> fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
>> ret = -1;
>> --
>> 2.17.1
>>
>
next prev parent reply other threads:[~2021-05-31 5:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-21 4:38 [PATCH v4] i386: Add ratelimit for bus locks acquired in guest Chenyi Qiang
2021-05-27 21:19 ` Eduardo Habkost
2021-05-31 5:14 ` Chenyi Qiang [this message]
2021-06-01 18:18 ` Eduardo Habkost
2021-06-01 20:10 ` Eduardo Habkost
2021-06-02 1:26 ` Chenyi Qiang
2021-07-27 8:28 ` Dr. David Alan Gilbert
2021-07-28 5:40 ` Chenyi Qiang
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