From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Upton Subject: Re: [PATCH v3 4/6] KVM: arm64/mmu: count KVM page table pages in pagetable stats Date: Tue, 26 Apr 2022 07:34:56 +0000 Message-ID: References: <20220426053904.3684293-1-yosryahmed@google.com> <20220426053904.3684293-5-yosryahmed@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=T6uVKqz/bxBh0XcbvcuRA0UyoUPF9VXe65F1cQD8y4Q=; b=ObEunFSl4crRLGfpGD9vb4uNjucdcW+SwMC5wjs68ErQM98eX2dd/1bhFqvb4MQrUZ aNBQiYOEZs6DAFrjwy4GxIX9P710BE5dNtb9ren8SoNbyoDCq1JSrqMW6bcxyN3g457u /+gBpA8szyFlMBKjZqPcqtIcg53tpCAgbfmBRZ+EQiSDL0bYkiLUkJAuAA+ESILGYbW5 jVcb61+A+66M7v7MKaJKTdQY27E/r9amtlm20dB0rHCxpqld0qjq5eRsqvCmPNleg1uA MTGwgfxKApBNNdQAeaBp8qoeybFa8FJ6gos+fYTUTeB4wg78apx7w8FkSb2oMxvxLXSe mDTA== Content-Disposition: inline In-Reply-To: <20220426053904.3684293-5-yosryahmed@google.com> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Yosry Ahmed Cc: Sean Christopherson , Huacai Chen , Aleksandar Markovic , Anup Patel , Atish Patra , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , James Morse , Catalin Marinas , Shameer Kolothum , Marc Zyngier 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 > --- > 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