On 10/01/19 19:06, Sean Christopherson wrote:
> Revert back to a dedicated (and slower) mechanism for handling the
> scenario where all MMIO shadow PTEs need to be zapped due to overflowing
> the MMIO generation number. The MMIO generation scenario is almost
> literally a one-in-a-million occurrence, i.e. is not a performance
> sensitive scenario.
>
> Restoring kvm_mmu_zap_mmio_sptes() leaves VM teardown as the only user
> of kvm_mmu_invalidate_zap_all_pages() and paves the way for removing
> the fast invalidate mechanism altogether.
>
> This reverts commit a8eca9dcc656a405a28ffba43f3d86a1ff0eb331.
>
> Cc: Xiao Guangrong <guangrong.xiao@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/mmu.c | 22 +++++++++++++++++++++-
> 2 files changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 31d05f0ef6d0..c2d49ad19a25 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -318,6 +318,7 @@ struct kvm_mmu_page {
> struct list_head link;
> struct hlist_node hash_link;
> bool unsync;
> + bool mmio_cached;
>
> /*
> * The following two entries are used to key the shadow page in the
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index bb56beb166e4..df41193aba38 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -386,6 +386,8 @@ static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
> mask |= (gpa & shadow_nonpresent_or_rsvd_mask)
> << shadow_nonpresent_or_rsvd_mask_len;
>
> + page_header(__pa(sptep))->mmio_cached = true;
> +
> trace_mark_mmio_spte(sptep, gfn, access, gen);
> mmu_spte_set(sptep, mask);
> }
> @@ -5932,6 +5934,24 @@ static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
> return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
> }
>
> +static void kvm_mmu_zap_mmio_sptes(struct kvm *kvm)
> +{
> + struct kvm_mmu_page *sp, *node;
> + LIST_HEAD(invalid_list);
> +
> + spin_lock(&kvm->mmu_lock);
> +restart:
> + list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
> + if (!sp->mmio_cached)
> + continue;
> + if (kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list))
> + goto restart;
This is potentially quadratic. If the "- 150" hack is removed, I'd
rather have a zap-all instead.
I understand it is a huge headache to squash the change at this point of
the series precisely, so it's okay to have a patch on top at the end.
Paolo
> + }
> +
> + kvm_mmu_commit_zap_page(kvm, &invalid_list);
> + spin_unlock(&kvm->mmu_lock);
> +}
> +
> void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, struct kvm_memslots *slots)
> {
> /*
> @@ -5940,7 +5960,7 @@ void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, struct kvm_memslots *slots)
> */
> if (unlikely((slots->generation & MMIO_GEN_MASK) == 0)) {
> kvm_debug_ratelimited("kvm: zapping shadow pages for mmio generation wraparound\n");
> - kvm_mmu_invalidate_zap_all_pages(kvm);
> + kvm_mmu_zap_mmio_sptes(kvm);
> }
> }
>
>
