On Wed, Jun 22, 2022, Paolo Bonzini wrote:
> From: David Matlack <dmatlack@xxxxxxxxxx>
>
> Currently KVM only zaps collapsible 4KiB SPTEs in the shadow MMU. This
> is fine for now since KVM never creates intermediate huge pages during
> dirty logging. In other words, KVM always replaces 1GiB pages directly
> with 4KiB pages, so there is no reason to look for collapsible 2MiB
> pages.
>
> However, this will stop being true once the shadow MMU participates in
> eager page splitting. During eager page splitting, each 1GiB is first
> split into 2MiB pages and then those are split into 4KiB pages. The
> intermediate 2MiB pages may be left behind if an error condition causes
> eager page splitting to bail early.
>
> No functional change intended.
>
> Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
> Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
> Message-Id: <20220516232138.1783324-20-dmatlack@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu/mmu.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 13a059ad5dc7..36bc49f08d60 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -6154,18 +6154,25 @@ static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
> return need_tlb_flush;
> }
>
> +static void kvm_rmap_zap_collapsible_sptes(struct kvm *kvm,
> + const struct kvm_memory_slot *slot)
> +{
> + /*
> + * Note, use KVM_MAX_HUGEPAGE_LEVEL - 1 since there's no need to zap
> + * pages that are already mapped at the maximum possible level.
> + */
> + if (slot_handle_level(kvm, slot, kvm_mmu_zap_collapsible_spte,
> + PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL - 1,
> + true))
Can you fix this up to put "true" on the previous line?
And if you do that, maybe also tweak the comment to reference "hugepage level"
instead of "possible level"?
---
arch/x86/kvm/mmu/mmu.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8825716060e4..34b0e85b26a4 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6450,12 +6450,11 @@ static void kvm_rmap_zap_collapsible_sptes(struct kvm *kvm,
const struct kvm_memory_slot *slot)
{
/*
- * Note, use KVM_MAX_HUGEPAGE_LEVEL - 1 since there's no need to zap
- * pages that are already mapped at the maximum possible level.
+ * Note, use KVM_MAX_HUGEPAGE_LEVEL - 1, there's no need to zap pages
+ * that are already mapped at the maximum hugepage level.
*/
if (slot_handle_level(kvm, slot, kvm_mmu_zap_collapsible_spte,
- PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL - 1,
- true))
+ PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL - 1, true))
kvm_arch_flush_remote_tlbs_memslot(kvm, slot);
}
base-commit: fd43332c2900db8ca852676f37f0ab423d0c369a
--
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