Re: [PATCH v8 05/14] KVM: Allow range-based TLB invalidation from common code

[Raghavendra Rao Ananta]

On Tue, Aug 8, 2023 at 11:09 PM Gavin Shan <gshan@xxxxxxxxxx> wrote:
>
> On 8/9/23 09:13, Raghavendra Rao Ananta wrote:
> > From: David Matlack <dmatlack@xxxxxxxxxx>
> >
> > Make kvm_flush_remote_tlbs_range() visible in common code and create a
> > default implementation that just invalidates the whole TLB.
> >
> > This paves the way for several future features/cleanups:
> >
> >   - Introduction of range-based TLBI on ARM.
> >   - Eliminating kvm_arch_flush_remote_tlbs_memslot()
> >   - Moving the KVM/x86 TDP MMU to common code.
> >
> > No functional change intended.
> >
> > Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
> > Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> > Reviewed-by: Gavin Shan <gshan@xxxxxxxxxx>
> > Reviewed-by: Shaoqin Huang <shahuang@xxxxxxxxxx>
> > Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
> > ---
> >   arch/x86/include/asm/kvm_host.h |  2 ++
> >   arch/x86/kvm/mmu/mmu.c          |  8 ++++----
> >   arch/x86/kvm/mmu/mmu_internal.h |  3 ---
> >   include/linux/kvm_host.h        | 12 ++++++++++++
> >   virt/kvm/kvm_main.c             | 13 +++++++++++++
> >   5 files changed, 31 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index a2d3cfc2eb75c..b547d17c58f63 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -1804,6 +1804,8 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
> >               return -ENOTSUPP;
> >   }
> >
> > +#define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
> > +
> >   #define kvm_arch_pmi_in_guest(vcpu) \
> >       ((vcpu) && (vcpu)->arch.handling_intr_from_guest)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index ec169f5c7dce2..6adbe6c870982 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -278,16 +278,16 @@ static inline bool kvm_available_flush_remote_tlbs_range(void)
> >       return kvm_x86_ops.flush_remote_tlbs_range;
> >   }
> >
> > -void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
> > -                              gfn_t nr_pages)
> > +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
> > +                                   u64 nr_pages)
> >   {
> >       int ret = -EOPNOTSUPP;
> >
> >       if (kvm_x86_ops.flush_remote_tlbs_range)
> >               ret = static_call(kvm_x86_flush_remote_tlbs_range)(kvm, start_gfn,
> >                                                                  nr_pages);
> > -     if (ret)
> > -             kvm_flush_remote_tlbs(kvm);
> > +
> > +     return ret;
> >   }
> >
>
> I guess @start_gfn can be renamed to @gfn, to be consistent with its declaration
> in include/linux/kvm_host.h and struct kvm_x86_ops::flush_remote_tlbs_range()
>
Oh, yes. I'll consider this change for v9 (if there are enough changes
and we plan to push one).

Thank you.
Raghavendra

> >   static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index);
> > diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> > index d39af5639ce97..86cb83bb34804 100644
> > --- a/arch/x86/kvm/mmu/mmu_internal.h
> > +++ b/arch/x86/kvm/mmu/mmu_internal.h
> > @@ -170,9 +170,6 @@ bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
> >                                   struct kvm_memory_slot *slot, u64 gfn,
> >                                   int min_level);
> >
> > -void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t start_gfn,
> > -                              gfn_t nr_pages);
> > -
> >   /* Flush the given page (huge or not) of guest memory. */
> >   static inline void kvm_flush_remote_tlbs_gfn(struct kvm *kvm, gfn_t gfn, int level)
> >   {
> > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> > index ade5d4500c2ce..f0be5d9c37dd1 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -1359,6 +1359,7 @@ int kvm_vcpu_yield_to(struct kvm_vcpu *target);
> >   void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu, bool yield_to_kernel_mode);
> >
> >   void kvm_flush_remote_tlbs(struct kvm *kvm);
> > +void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages);
> >
> >   #ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE
> >   int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min);
> > @@ -1488,6 +1489,17 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
> >   int kvm_arch_flush_remote_tlbs(struct kvm *kvm);
> >   #endif
> >
> > +#ifndef __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
> > +static inline int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm,
> > +                                                 gfn_t gfn, u64 nr_pages)
> > +{
> > +     return -EOPNOTSUPP;
> > +}
> > +#else
> > +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm,
> > +                                   gfn_t gfn, u64 nr_pages);
> > +#endif
> > +
> >   #ifdef __KVM_HAVE_ARCH_NONCOHERENT_DMA
> >   void kvm_arch_register_noncoherent_dma(struct kvm *kvm);
> >   void kvm_arch_unregister_noncoherent_dma(struct kvm *kvm);
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index d6b0507861550..26e91000f579d 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -366,6 +366,19 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
> >   }
> >   EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);
> >
> > +void kvm_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages)
> > +{
> > +     if (!kvm_arch_flush_remote_tlbs_range(kvm, gfn, nr_pages))
> > +             return;
> > +
> > +     /*
> > +      * Fall back to a flushing entire TLBs if the architecture range-based
> > +      * TLB invalidation is unsupported or can't be performed for whatever
> > +      * reason.
> > +      */
> > +     kvm_flush_remote_tlbs(kvm);
> > +}
> > +
> >   static void kvm_flush_shadow_all(struct kvm *kvm)
> >   {
> >       kvm_arch_flush_shadow_all(kvm);
>
> Thanks,
> Gavin
>