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

[Chenyi Qiang]

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