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[217.140.101.70]) by mx.google.com with ESMTP id r2si3377050ejf.139.2019.03.12.04.43.07 for ; Tue, 12 Mar 2019 04:43:07 -0700 (PDT) Received-SPF: pass (google.com: domain of suzuki.poulose@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of suzuki.poulose@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=suzuki.poulose@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 521B1374; Tue, 12 Mar 2019 04:43:06 -0700 (PDT) Received: from [10.1.196.93] (en101.cambridge.arm.com [10.1.196.93]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 349683F59C; Tue, 12 Mar 2019 04:43:04 -0700 (PDT) Subject: Re: [PATCH] KVM: ARM: Remove pgtable page standard functions from stage-2 page tables To: anshuman.khandual@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, mark.rutland@arm.com, yuzhao@google.com Cc: linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org References: <20190312005749.30166-3-yuzhao@google.com> <1552357142-636-1-git-send-email-anshuman.khandual@arm.com> <5b82c7c4-93cc-2820-46ad-3fb731a0eefc@arm.com> <2d00c35d-ae10-ba4a-9b34-939fcf2b2f49@arm.com> From: Suzuki K Poulose Message-ID: <3be0b7e0-2ef8-babb-88c9-d229e0fdd220@arm.com> Date: Tue, 12 Mar 2019 11:43:02 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <2d00c35d-ae10-ba4a-9b34-939fcf2b2f49@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12/03/2019 11:31, Anshuman Khandual wrote: > > > On 03/12/2019 04:07 PM, Suzuki K Poulose wrote: >> Hi Anshuman, >> >> On 12/03/2019 02:19, Anshuman Khandual wrote: >>> ARM64 standard pgtable functions are going to use pgtable_page_[ctor|dtor] >>> or pgtable_pmd_page_[ctor|dtor] constructs. At present KVM guest stage-2 >>> PUD|PMD|PTE level page tabe pages are allocated with __get_free_page() >>> via mmu_memory_cache_alloc() but released with standard pud|pmd_free() or >>> pte_free_kernel(). These will fail once they start calling into pgtable_ >>> [pmd]_page_dtor() for pages which never originally went through respective >>> constructor functions. Hence convert all stage-2 page table page release >>> functions to call buddy directly while freeing pages. >>> >>> Signed-off-by: Anshuman Khandual >>> --- >>>   arch/arm/include/asm/stage2_pgtable.h   | 4 ++-- >>>   arch/arm64/include/asm/stage2_pgtable.h | 4 ++-- >>>   virt/kvm/arm/mmu.c                      | 2 +- >>>   3 files changed, 5 insertions(+), 5 deletions(-) >>> >>> diff --git a/arch/arm/include/asm/stage2_pgtable.h b/arch/arm/include/asm/stage2_pgtable.h >>> index de2089501b8b..417a3be00718 100644 >>> --- a/arch/arm/include/asm/stage2_pgtable.h >>> +++ b/arch/arm/include/asm/stage2_pgtable.h >>> @@ -32,14 +32,14 @@ >>>   #define stage2_pgd_present(kvm, pgd)        pgd_present(pgd) >>>   #define stage2_pgd_populate(kvm, pgd, pud)    pgd_populate(NULL, pgd, pud) >>>   #define stage2_pud_offset(kvm, pgd, address)    pud_offset(pgd, address) >>> -#define stage2_pud_free(kvm, pud)        pud_free(NULL, pud) >>> +#define stage2_pud_free(kvm, pud)        free_page((unsigned long)pud) >> >> That must be a NOP, as we don't have pud on arm32 (we have 3 level table). >> The pud_* helpers here all fallback to the generic no-pud helpers. > Which is the following here for pud_free() > > #define pud_free(mm, x) do { } while (0) > > On arm64 its protected by kvm_stage2_has_pud() helper before calling into pud_free(). > In this case even though applicable pud_free() is NOP, it is still misleading. If we > are sure about page table level will always remain three it can directly have a NOP > (do/while) in there. > Yes, it is fixed for arm32 and you could have it as do {} while (0), which is what I meant by NOP. On arm64, we had varied number of levels depending on the PAGE_SIZE and now due to the dynamic IPA, hence the check. Cheers Suzuki