RE: [PATCH v3] KVM: x86: enable dirty log gradually in small chunks

["Zhoujian (jay)" <jianjay.zhou@huawei.com>]

> -----Original Message-----
> From: Peter Xu [mailto:peterx@redhat.com]

[...]

> > > > > @@ -3320,6 +3326,10 @@ static long
> > > > kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
> > > > >  	case KVM_CAP_COALESCED_PIO:
> > > > >  		return 1;
> > > > >  #endif
> > > > > +#ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
> > > > > +	case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2:
> > > > > +		return KVM_DIRTY_LOG_MANUAL_CAPS;
> > > >
> > > > We probably can only return the new feature bit when with CONFIG_X86?

Since the meaning of KVM_DIRTY_LOG_MANUAL_CAPS will change accordingly in
different archs, we can use it in kvm_vm_ioctl_enable_cap_generic, how about:

@@ -3347,11 +3351,17 @@ static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
 {
        switch (cap->cap) {
 #ifdef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
-       case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2:
-               if (cap->flags || (cap->args[0] & ~1))
+       case KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2: {
+               u64 allowed_options = KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE;
+
+               if (cap->args[0] & KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE)
+                       allowed_options = KVM_DIRTY_LOG_MANUAL_CAPS;
+
+               if (cap->flags || (cap->args[0] & ~allowed_options))
                        return -EINVAL;
                kvm->manual_dirty_log_protect = cap->args[0];
                return 0;
+       }

[...]

>> How about:
> >
> > ==========
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h
> > b/arch/x86/include/asm/kvm_host.h index 40a0c0fd95ca..fcffaf8a6964
> > 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1697,4 +1697,7 @@ static inline int kvm_cpu_get_apicid(int mps_cpu)
> >  #define GET_SMSTATE(type, buf, offset)         \
> >         (*(type *)((buf) + (offset) - 0x7e00))
> >
> > +#define KVM_DIRTY_LOG_MANUAL_CAPS
> (KVM_DIRTY_LOG_MANUAL_PROTECT | \
> > +
> KVM_DIRTY_LOG_INITIALLY_SET)
> > +
> >  #endif /* _ASM_X86_KVM_HOST_H */
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index
> > e89eb67356cb..39d49802ee87 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -1410,4 +1410,8 @@ int kvm_vm_create_worker_thread(struct kvm *kvm,
> kvm_vm_thread_fn_t thread_fn,
> >                                 uintptr_t data, const char *name,
> >                                 struct task_struct **thread_ptr);
> >
> > +#ifndef KVM_DIRTY_LOG_MANUAL_CAPS
> > +#define KVM_DIRTY_LOG_MANUAL_CAPS
> KVM_DIRTY_LOG_MANUAL_PROTECT
> > +#endif
> > +
> 
> Hmm... Maybe this won't work, because I saw that asm/kvm_host.h and
> linux/kvm_host.h has no dependency between each other (which I thought they
> had).  Right now in most cases linux/ header can be included earlier than the
> asm/ header in C files.  So intead, maybe we can move these lines into
> kvm_main.c directly.

I did some tests on x86, and it works. Looks good to me.

> 
> (I'm thinking ideally linux/kvm_host.h should include asm/kvm_host.h  within
> itself, then C files should not include asm/kvm_host.h  directly. However I dare
> not try that right now without being able to  test compile on all archs...)
> 
But, I see include/linux/kvm_host.h has already included asm/kvm_host.h in the
upstream. Do I understand your meaning correctly?

Regards,
Jay Zhou