Re: [PATCH v4] i386: Add ratelimit for bus locks acquired in guest

[Chenyi Qiang <chenyi.qiang@intel.com>]

On 6/2/2021 4:10 AM, Eduardo Habkost wrote:
> On Tue, Jun 01, 2021 at 02:18:37PM -0400, Eduardo Habkost wrote:
>> On Mon, May 31, 2021 at 01:14:54PM +0800, Chenyi Qiang wrote:
>>>
>>>
>>> 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.
>>
>> I'm queueing on x86-next, thanks!
> 
> This breaks the build.  Is there a linux-headers update patch I've missed?
> 

Thanks for the queue and sorry for forgetting to submit the 
linux-headers update patch.

> ../target/i386/kvm/kvm.c: In function 'kvm_arch_init':
> ../target/i386/kvm/kvm.c:2322:42: error: 'KVM_CAP_X86_BUS_LOCK_EXIT' undeclared (first use in this function); did you mean 'KVM_CAP_X86_DISABLE_EXITS'?
>               ret = kvm_check_extension(s, KVM_CAP_X86_BUS_LOCK_EXIT);
>                                            ^~~~~~~~~~~~~~~~~~~~~~~~~
>                                            KVM_CAP_X86_DISABLE_EXITS
>