linux-kernel - Re: [PATCH 16/21] KVM: arm64: Drop @max param from mmu_topup_memory

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Date:   Wed, 10 Jun 2020 15:00:47 -0700
From:   Ben Gardon <bgardon@...gle.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Marc Zyngier <maz@...nel.org>, Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peter Feiner <pfeiner@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        Christoffer Dall <christoffer.dall@....com>
Subject: Re: [PATCH 16/21] KVM: arm64: Drop @max param from mmu_topup_memory_cache()

On Fri, Jun 5, 2020 at 2:39 PM Sean Christopherson
<sean.j.christopherson@...el.com> wrote:
>
> Replace the @max param in mmu_topup_memory_cache() and instead use
> ARRAY_SIZE() to terminate the loop to fill the cache.  This removes a
> BUG_ON() and sets the stage for moving arm64 to the common memory cache
> implementation.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/arm64/kvm/mmu.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index a1f6bc70c4e4..9398b66f8a87 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -124,15 +124,13 @@ static void stage2_dissolve_pud(struct kvm *kvm, phys_addr_t addr, pud_t *pudp)
>         put_page(virt_to_page(pudp));
>  }
>
> -static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
> -                                 int min, int max)
> +static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache, int min)
>  {
>         void *page;
>
> -       BUG_ON(max > KVM_NR_MEM_OBJS);
KVM_NR_MEM_OBJS should be undefined as of patch 14 in this series. I'd
recommend changing this to use the new constant you defined in that
patch.
>         if (cache->nobjs >= min)
>                 return 0;
> -       while (cache->nobjs < max) {
> +       while (cache->nobjs < ARRAY_SIZE(cache->objects)) {
>                 page = (void *)__get_free_page(GFP_PGTABLE_USER);
>                 if (!page)
>                         return -ENOMEM;
> @@ -1356,8 +1354,7 @@ int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,
>                         pte = kvm_s2pte_mkwrite(pte);
>
>                 ret = mmu_topup_memory_cache(&cache,
> -                                            kvm_mmu_cache_min_pages(kvm),
> -                                            KVM_NR_MEM_OBJS);
See above, KVM_NR_MEM_OBJS is undefined as of patch 14.
> +                                            kvm_mmu_cache_min_pages(kvm));
>                 if (ret)
>                         goto out;
>                 spin_lock(&kvm->mmu_lock);
> @@ -1737,8 +1734,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>         up_read(&current->mm->mmap_sem);
>
>         /* We need minimum second+third level pages */
> -       ret = mmu_topup_memory_cache(memcache, kvm_mmu_cache_min_pages(kvm),
> -                                    KVM_NR_MEM_OBJS);
See above, KVM_NR_MEM_OBJS is undefined as of patch 14.
> +       ret = mmu_topup_memory_cache(memcache, kvm_mmu_cache_min_pages(kvm));
>         if (ret)
>                 return ret;
>
> --
> 2.26.0
>