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

[Eduardo Habkost]

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?

../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

-- 
Eduardo