Hi Yosry, On Tue, Apr 26, 2022 at 05:39:02AM +0000, Yosry Ahmed wrote: > Count the pages used by KVM in arm64 for page tables in pagetable stats. > > Account pages allocated for PTEs in pgtable init functions and > kvm_set_table_pte(). > > Since most page table pages are freed using put_page(), add a helper > function put_pte_page() that checks if this is the last ref for a pte > page before putting it, and unaccounts stats accordingly. > > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > --- > arch/arm64/kernel/image-vars.h | 3 ++ > arch/arm64/kvm/hyp/pgtable.c | 50 +++++++++++++++++++++------------- > 2 files changed, 34 insertions(+), 19 deletions(-) > > diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h > index 241c86b67d01..25bf058714f6 100644 > --- a/arch/arm64/kernel/image-vars.h > +++ b/arch/arm64/kernel/image-vars.h > @@ -143,6 +143,9 @@ KVM_NVHE_ALIAS(__hyp_rodata_end); > /* pKVM static key */ > KVM_NVHE_ALIAS(kvm_protected_mode_initialized); > > +/* Called by kvm_account_pgtable_pages() to update pagetable stats */ > +KVM_NVHE_ALIAS(__mod_lruvec_page_state); > + > #endif /* CONFIG_KVM */ > > #endif /* __ARM64_KERNEL_IMAGE_VARS_H */ > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 2cb3867eb7c2..53e13c3313e9 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -152,6 +152,7 @@ static void kvm_set_table_pte(kvm_pte_t *ptep, kvm_pte_t *childp, > > WARN_ON(kvm_pte_valid(old)); > smp_store_release(ptep, pte); > + kvm_account_pgtable_pages((void *)childp, +1); What page tables do we want to account? KVM on ARM manages several page tables. For regular KVM, the host kernel manages allocations for the hyp stage 1 tables in addition to the stage 2 tables used for a particular VM. The former is system overhead whereas the latter could be attributed to a guest VM. I imagine protected KVM is out of scope, since it actually manages its own allocations outside of the host kernel. Given this, I would recommend adding the accounting hooks to mmu.c as that is where we alloc/free table pages and it is in the host address space. kvm_s2_mm_ops and kvm_hyp_mm_ops point to all the relevant functions, though the latter is only relevant if we want to count system page tables too. -- Thanks, Oliver
