Re: [PATCH v2 1/3] kvm: x86: Add a hook for arch specific dirty logging emulation

["Huang, Kai" <kai.huang@xxxxxxxxxxxxxxx>]

On 5/11/2017 3:53 AM, Bandan Das wrote:
> Hi Kai,
>
> "Huang, Kai" <kai.huang@xxxxxxxxxxxxxxx> writes:
>
> > On 5/6/2017 7:25 AM, Bandan Das wrote:
> > > When KVM updates accessed/dirty bits, this hook can be used
> > > to invoke an arch specific function that implements/emulates
> > > dirty logging such as PML.
> > >
> > > Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
> > > ---
> > >  arch/x86/include/asm/kvm_host.h |  2 ++
> > >  arch/x86/kvm/mmu.c              | 15 +++++++++++++++
> > >  arch/x86/kvm/mmu.h              |  1 +
> > >  arch/x86/kvm/paging_tmpl.h      |  4 ++++
> > >  4 files changed, 22 insertions(+)
> > >
> > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > > index f5bddf92..9c761fe 100644
> > > --- a/arch/x86/include/asm/kvm_host.h
> > > +++ b/arch/x86/include/asm/kvm_host.h
> > > @@ -1020,6 +1020,8 @@ struct kvm_x86_ops {
> > >  	void (*enable_log_dirty_pt_masked)(struct kvm *kvm,
> > >  					   struct kvm_memory_slot *slot,
> > >  					   gfn_t offset, unsigned long mask);
> > > +	int (*write_log_dirty)(struct kvm_vcpu *vcpu);
> >
> > Hi,
> >
> > Thanks for adding PML to nested support!
> >
> > IMHO this callback is only used for write L2's dirty gpa to L1's PML
> > buffer, so probably it's better to change the name to something like:
> > nested_write_log_dirty.
>
> The name was meant more to signify what it does: i.e. write dirty log rather
> than where in the hierarchy it's being used :) But I guess, a nested_ prefix
> doesn't hurt either.

Hi Bandan,

I was just suggesting. You and Paolo still make the decision :)

Thanks,
-Kai
> Bandan
>
> > Thanks,
> > -Kai
> >
> > > +
> > >  	/* pmu operations of sub-arch */
> > >  	const struct kvm_pmu_ops *pmu_ops;
> > >
> > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > > index 5586765..5d3376f 100644
> > > --- a/arch/x86/kvm/mmu.c
> > > +++ b/arch/x86/kvm/mmu.c
> > > @@ -1498,6 +1498,21 @@ void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
> > >  		kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask);
> > >  }
> > >
> > > +/**
> > > + * kvm_arch_write_log_dirty - emulate dirty page logging
> > > + * @vcpu: Guest mode vcpu
> > > + *
> > > + * Emulate arch specific page modification logging for the
> > > + * nested hypervisor
> > > + */
> > > +int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu)
> > > +{
> > > +	if (kvm_x86_ops->write_log_dirty)
> > > +		return kvm_x86_ops->write_log_dirty(vcpu);
> > > +
> > > +	return 0;
> > > +}
> >
> > kvm_nested_arch_write_log_dirty?
> >
> > > +
> > >  bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
> > >  				    struct kvm_memory_slot *slot, u64 gfn)
> > >  {
> > > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> > > index d8ccb32..2797580 100644
> > > --- a/arch/x86/kvm/mmu.h
> > > +++ b/arch/x86/kvm/mmu.h
> > > @@ -202,4 +202,5 @@ void kvm_mmu_gfn_disallow_lpage(struct kvm_memory_slot *slot, gfn_t gfn);
> > >  void kvm_mmu_gfn_allow_lpage(struct kvm_memory_slot *slot, gfn_t gfn);
> > >  bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
> > >  				    struct kvm_memory_slot *slot, u64 gfn);
> > > +int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);
> > >  #endif
> > > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> > > index 314d207..5624174 100644
> > > --- a/arch/x86/kvm/paging_tmpl.h
> > > +++ b/arch/x86/kvm/paging_tmpl.h
> > > @@ -226,6 +226,10 @@ static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
> > >  		if (level == walker->level && write_fault &&
> > >  				!(pte & PT_GUEST_DIRTY_MASK)) {
> > >  			trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));
> > > +#if PTTYPE == PTTYPE_EPT
> > > +			if (kvm_arch_write_log_dirty(vcpu))
> > > +				return -EINVAL;
> > > +#endif
> > >  			pte |= PT_GUEST_DIRTY_MASK;
> > >  		}
> > >  		if (pte == orig_pte)