From mboxrd@z Thu Jan 1 00:00:00 1970 From: Suzuki K Poulose Subject: Re: [PATCH v9 1/8] KVM: arm/arm64: Share common code in user_mem_abort() Date: Mon, 3 Dec 2018 13:37:37 +0000 Message-ID: <8fd34e5f-7d75-4de2-3fee-d6d70805685c@arm.com> References: <20181031175745.18650-1-punit.agrawal@arm.com> <20181031175745.18650-2-punit.agrawal@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 73DA84A333 for ; Mon, 3 Dec 2018 08:37:42 -0500 (EST) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hWa+xf+HwW1j for ; Mon, 3 Dec 2018 08:37:41 -0500 (EST) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id F31904A1FA for ; Mon, 3 Dec 2018 08:37:40 -0500 (EST) In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Anshuman Khandual , kvmarm@lists.cs.columbia.edu Cc: marc.zyngier@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: kvmarm@lists.cs.columbia.edu Hi Anshuman, On 03/12/2018 12:11, Anshuman Khandual wrote: > > > On 10/31/2018 11:27 PM, Punit Agrawal wrote: >> The code for operations such as marking the pfn as dirty, and >> dcache/icache maintenance during stage 2 fault handling is duplicated >> between normal pages and PMD hugepages. >> >> Instead of creating another copy of the operations when we introduce >> PUD hugepages, let's share them across the different pagesizes. >> >> Signed-off-by: Punit Agrawal >> Reviewed-by: Suzuki K Poulose >> Cc: Christoffer Dall >> Cc: Marc Zyngier >> --- >> virt/kvm/arm/mmu.c | 49 ++++++++++++++++++++++++++++------------------ >> 1 file changed, 30 insertions(+), 19 deletions(-) >> >> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >> index 5eca48bdb1a6..59595207c5e1 100644 >> --- a/virt/kvm/arm/mmu.c >> +++ b/virt/kvm/arm/mmu.c >> @@ -1475,7 +1475,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >> unsigned long fault_status) >> { >> int ret; >> - bool write_fault, exec_fault, writable, hugetlb = false, force_pte = false; >> + bool write_fault, exec_fault, writable, force_pte = false; >> unsigned long mmu_seq; >> gfn_t gfn = fault_ipa >> PAGE_SHIFT; >> struct kvm *kvm = vcpu->kvm; >> @@ -1484,7 +1484,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >> kvm_pfn_t pfn; >> pgprot_t mem_type = PAGE_S2; >> bool logging_active = memslot_is_logging(memslot); >> - unsigned long flags = 0; >> + unsigned long vma_pagesize, flags = 0; > > A small nit s/vma_pagesize/pagesize. Why call it VMA ? Its implicit. May be we could call it mapsize. pagesize is confusing. > >> >> write_fault = kvm_is_write_fault(vcpu); >> exec_fault = kvm_vcpu_trap_is_iabt(vcpu); >> @@ -1504,10 +1504,16 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >> return -EFAULT; >> } >> >> - if (vma_kernel_pagesize(vma) == PMD_SIZE && !logging_active) { >> - hugetlb = true; >> + vma_pagesize = vma_kernel_pagesize(vma); >> + if (vma_pagesize == PMD_SIZE && !logging_active) { >> gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT; >> } else { >> + /* >> + * Fallback to PTE if it's not one of the Stage 2 >> + * supported hugepage sizes >> + */ >> + vma_pagesize = PAGE_SIZE; > > This seems redundant and should be dropped. vma_kernel_pagesize() here either > calls hugetlb_vm_op_pagesize (via hugetlb_vm_ops->pagesize) or simply returns > PAGE_SIZE. The vm_ops path is taken if the QEMU VMA covering any given HVA is > backed either by HugeTLB pages or simply normal pages. vma_pagesize would > either has a value of PMD_SIZE (HugeTLB hstate based) or PAGE_SIZE. Hence if > its not PMD_SIZE it must be PAGE_SIZE which should not be assigned again. We may want to force using the PTE mappings when logging_active (e.g, migration ?) to prevent keep tracking of huge pages. So the check is still valid. > >> + >> /* >> * Pages belonging to memslots that don't have the same >> * alignment for userspace and IPA cannot be mapped using >> @@ -1573,23 +1579,33 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >> if (mmu_notifier_retry(kvm, mmu_seq)) >> goto out_unlock; >> >> - if (!hugetlb && !force_pte) >> - hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa); >> + if (vma_pagesize == PAGE_SIZE && !force_pte) { >> + /* >> + * Only PMD_SIZE transparent hugepages(THP) are >> + * currently supported. This code will need to be >> + * updated to support other THP sizes. >> + */ > > This comment belongs to transparent_hugepage_adjust() but not here. I think this is relevant here than in thp_adjust, unless we rename the function below to something generic, handle_hugepage_adjust(). >> + if (transparent_hugepage_adjust(&pfn, &fault_ipa)) >> + vma_pagesize = PMD_SIZE; > > IIUC transparent_hugepage_adjust() is only getting called here. Instead of > returning 'true' when it is able to detect a huge page backing and doing > an adjustment there after, it should rather return THP size (PMD_SIZE) to > accommodate probable multi size THP support in future . That makes sense. > >> + } >> + >> + if (writable) >> + kvm_set_pfn_dirty(pfn); >> >> - if (hugetlb) { >> + if (fault_status != FSC_PERM) >> + clean_dcache_guest_page(pfn, vma_pagesize); >> + >> + if (exec_fault) >> + invalidate_icache_guest_page(pfn, vma_pagesize); >> + >> + if (vma_pagesize == PMD_SIZE) { >> pmd_t new_pmd = pfn_pmd(pfn, mem_type); >> new_pmd = pmd_mkhuge(new_pmd); >> - if (writable) { >> + if (writable) >> new_pmd = kvm_s2pmd_mkwrite(new_pmd); >> - kvm_set_pfn_dirty(pfn); >> - } >> - >> - if (fault_status != FSC_PERM) >> - clean_dcache_guest_page(pfn, PMD_SIZE); >> >> if (exec_fault) { >> new_pmd = kvm_s2pmd_mkexec(new_pmd); >> - invalidate_icache_guest_page(pfn, PMD_SIZE); >> } else if (fault_status == FSC_PERM) { >> /* Preserve execute if XN was already cleared */ >> if (stage2_is_exec(kvm, fault_ipa)) >> @@ -1602,16 +1618,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, >> >> if (writable) { >> new_pte = kvm_s2pte_mkwrite(new_pte); >> - kvm_set_pfn_dirty(pfn); >> mark_page_dirty(kvm, gfn); >> } >> >> - if (fault_status != FSC_PERM) >> - clean_dcache_guest_page(pfn, PAGE_SIZE); >> - >> if (exec_fault) { >> new_pte = kvm_s2pte_mkexec(new_pte); >> - invalidate_icache_guest_page(pfn, PAGE_SIZE); >> } else if (fault_status == FSC_PERM) { >> /* Preserve execute if XN was already cleared */ >> if (stage2_is_exec(kvm, fault_ipa)) >> > > kvm_set_pfn_dirty, clean_dcache_guest_page, invalidate_icache_guest_page > can all be safely moved before setting the page table entries either as > PMD or PTE. I think this is what we do currently. So I assume this is fine. Cheers Suzuki