Re: [PATCH v2 2/5] KVM: MMU: Convert remote flushes to kvm_mark_tlb_dirty() and a conditional flush

[Takuya Yoshikawa]

On Thu, 17 May 2012 13:24:41 +0300
Avi Kivity  wrote:

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2256f51..a2149d8 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3130,7 +3130,9 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, struct 
> kvm_dirty_log *log)
>   kvm_mmu_write_protect_pt_masked(kvm, memslot, offset, mask);
>   }
>   if (is_dirty)
> - kvm_flush_remote_tlbs(kvm);
> + kvm_mark_tlb_dirty(kvm);
> +
> + kvm_cond_flush_remote_tlbs(kvm);
>  
>   spin_unlock(&kvm->mmu_lock);

Any reason not to move this flush outside of the mmu_lock in this
patch series?

Unlike other rmap write protections, this one seems to be simple.

Takuya
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Re: [PATCH v2 2/5] KVM: MMU: Convert remote flushes to kvm_mark_tlb_dirty() and a conditional flush

[Marcelo Tosatti]

On Thu, May 17, 2012 at 01:24:41PM +0300, Avi Kivity wrote:
> This allows us to later move the actual flush out of protection of the
> mmu spinlock, provided there are no additional dependencies.
> 
> Constructs of the form
> 
> if (pred)
> kvm_flush_remote_tlbs(kvm)
> 
> are converted to
> 
> if (pred)
> kvm_mark_tlb_dirty(kvm)
> 
> kvm_cond_flush_remote_tlbs(kvm)
> 
> so that if another thread caused pred to transition from true to false,
> but has not yet flushed the tlb, we notice it and flush it before proceeding.
> 
> Signed-off-by: Avi Kivity 
> ---
>  arch/ia64/kvm/kvm-ia64.c   |6 --
>  arch/x86/kvm/mmu.c |   45 
> +++-
>  arch/x86/kvm/paging_tmpl.h |4 +++-
>  arch/x86/kvm/x86.c |4 +++-
>  virt/kvm/kvm_main.c|4 +++-
>  5 files changed, 41 insertions(+), 22 deletions(-)
> 
> diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
> index bd77cb5..a4a92d8 100644
> --- a/arch/ia64/kvm/kvm-ia64.c
> +++ b/arch/ia64/kvm/kvm-ia64.c
> @@ -1628,7 +1628,8 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>  
>  void kvm_arch_flush_shadow(struct kvm *kvm)
>  {
> - kvm_flush_remote_tlbs(kvm);
> + kvm_mark_tlb_dirty(kvm);
> + kvm_cond_flush_remote_tlbs(kvm);
>  }
>  
>  long kvm_arch_dev_ioctl(struct file *filp,
> @@ -1853,10 +1854,11 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
>  
>   /* If nothing is dirty, don't bother messing with page tables. */
>   if (is_dirty) {
> - kvm_flush_remote_tlbs(kvm);
> + kvm_mark_tlb_dirty(kvm);
>   n = kvm_dirty_bitmap_bytes(memslot);
>   memset(memslot->dirty_bitmap, 0, n);
>   }
> + kvm_cond_flush_remote_tlbs(kvm);
>   r = 0;
>  out:
>   mutex_unlock(&kvm->slots_lock);
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 07424cf..03a9c80 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1170,7 +1170,9 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned 
> long *rmapp,
>   }
>  
>   if (need_flush)
> - kvm_flush_remote_tlbs(kvm);
> + kvm_mark_tlb_dirty(kvm);
> +
> + kvm_cond_flush_remote_tlbs(kvm);
>  
>   return 0;
>  }
> @@ -1294,7 +1296,8 @@ static void rmap_recycle(struct kvm_vcpu *vcpu, u64 
> *spte, gfn_t gfn)
>   rmapp = gfn_to_rmap(vcpu->kvm, gfn, sp->role.level);
>  
>   kvm_unmap_rmapp(vcpu->kvm, rmapp, 0);
> - kvm_flush_remote_tlbs(vcpu->kvm);
> + kvm_mark_tlb_dirty(vcpu->kvm);
> + kvm_cond_flush_remote_tlbs(vcpu->kvm);
>  }
>  
>  int kvm_age_hva(struct kvm *kvm, unsigned long hva)
> @@ -1697,7 +1700,9 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
>   protected |= rmap_write_protect(vcpu->kvm, sp->gfn);
>  
>   if (protected)
> - kvm_flush_remote_tlbs(vcpu->kvm);
> + kvm_mark_tlb_dirty(vcpu->kvm);
> +
> + kvm_cond_flush_remote_tlbs(vcpu->kvm);
>  
>   for_each_sp(pages, sp, parents, i) {
>   kvm_sync_page(vcpu, sp, &invalid_list);
> @@ -1786,7 +1791,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct 
> kvm_vcpu *vcpu,
>   &vcpu->kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)]);
>   if (!direct) {
>   if (rmap_write_protect(vcpu->kvm, gfn))
> - kvm_flush_remote_tlbs(vcpu->kvm);
> + kvm_mark_tlb_dirty(vcpu->kvm);
> + kvm_cond_flush_remote_tlbs(vcpu->kvm);
>   if (level > PT_PAGE_TABLE_LEVEL && need_sync)
>   kvm_sync_pages(vcpu, gfn);
>  
> @@ -1861,7 +1867,8 @@ static void drop_large_spte(struct kvm_vcpu *vcpu, u64 
> *sptep)
>   if (is_large_pte(*sptep)) {
>   drop_spte(vcpu->kvm, sptep);
>   --vcpu->kvm->stat.lpages;
> - kvm_flush_remote_tlbs(vcpu->kvm);
> + kvm_mark_tlb_dirty(vcpu->kvm);
> + kvm_cond_flush_remote_tlbs(vcpu->kvm);
>   }
>  }
>  
> @@ -1883,7 +1890,8 @@ static void validate_direct_spte(struct kvm_vcpu *vcpu, 
> u64 *sptep,
>   return;
>  
>   drop_parent_pte(child, sptep);
> - kvm_flush_remote_tlbs(vcpu->kvm);
> + kvm_mark_tlb_dirty(vcpu->kvm);
> + kvm_cond_flush_remote_tlbs(vcpu->kvm);
>   }
>  }
>  
> @@ -2021,7 +2029,8 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm,
>   if (list_empty(invalid_list))
>   return;
>  
> - kvm_flush_remote_tlbs(kvm);
> + kvm_mark_tlb_dirty(kvm);
> + kvm_cond_flush_remote_tlbs(kvm);
>  
>   if (atomic_read(&kvm->arch.reader_counter)) {
>   kvm_mmu_isolate_pages(invalid_list);
> @@ -2344,7 +2353,9 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>* might be cached on a CPU's TLB.
>*/
>   if (is_writable_pte(entry) && !is_writable_pte(*sptep))
> -