From fd6f17bade2147b31198ad00b22d3acf5a398aec Mon Sep 17 00:00:00 2001 From: Keqian Zhu Date: Fri, 7 May 2021 19:03:21 +0800 Subject: [PATCH 1/2] KVM: arm64: Remove the creation time's mapping of MMIO regions The MMIO regions may be unmapped for many reasons and can be remapped by stage2 fault path. Map MMIO regions at creation time becomes a minor optimization and makes these two mapping path hard to sync. Remove the mapping code while keep the useful sanity check. Signed-off-by: Keqian Zhu Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20210507110322.23348-2-zhukeqian1@huawei.com --- arch/arm64/kvm/mmu.c | 38 +++----------------------------------- 1 file changed, 3 insertions(+), 35 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index c10207fed2f3..e982178c8c72 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1346,7 +1346,6 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, { hva_t hva = mem->userspace_addr; hva_t reg_end = hva + mem->memory_size; - bool writable = !(mem->flags & KVM_MEM_READONLY); int ret = 0; if (change != KVM_MR_CREATE && change != KVM_MR_MOVE && @@ -1363,8 +1362,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, mmap_read_lock(current->mm); /* * A memory region could potentially cover multiple VMAs, and any holes - * between them, so iterate over all of them to find out if we can map - * any of them right now. + * between them, so iterate over all of them. * * +--------------------------------------------+ * +---------------+----------------+ +----------------+ @@ -1375,51 +1373,21 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, */ do { struct vm_area_struct *vma; - hva_t vm_start, vm_end; vma = find_vma_intersection(current->mm, hva, reg_end); if (!vma) break; - /* - * Take the intersection of this VMA with the memory region - */ - vm_start = max(hva, vma->vm_start); - vm_end = min(reg_end, vma->vm_end); - if (vma->vm_flags & VM_PFNMAP) { - gpa_t gpa = mem->guest_phys_addr + - (vm_start - mem->userspace_addr); - phys_addr_t pa; - - pa = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT; - pa += vm_start - vma->vm_start; - /* IO region dirty page logging not allowed */ if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) { ret = -EINVAL; - goto out; - } - - ret = kvm_phys_addr_ioremap(kvm, gpa, pa, - vm_end - vm_start, - writable); - if (ret) break; + } } - hva = vm_end; + hva = min(reg_end, vma->vm_end); } while (hva < reg_end); - if (change == KVM_MR_FLAGS_ONLY) - goto out; - - spin_lock(&kvm->mmu_lock); - if (ret) - unmap_stage2_range(&kvm->arch.mmu, mem->guest_phys_addr, mem->memory_size); - else if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) - stage2_flush_memslot(kvm, memslot); - spin_unlock(&kvm->mmu_lock); -out: mmap_read_unlock(current->mm); return ret; } From 2aa53d68cee6603931f73b28ef6b51ff3fde9397 Mon Sep 17 00:00:00 2001 From: Keqian Zhu Date: Fri, 7 May 2021 19:03:22 +0800 Subject: [PATCH 2/2] KVM: arm64: Try stage2 block mapping for host device MMIO The MMIO region of a device maybe huge (GB level), try to use block mapping in stage2 to speedup both map and unmap. Compared to normal memory mapping, we should consider two more points when try block mapping for MMIO region: 1. For normal memory mapping, the PA(host physical address) and HVA have same alignment within PUD_SIZE or PMD_SIZE when we use the HVA to request hugepage, so we don't need to consider PA alignment when verifing block mapping. But for device memory mapping, the PA and HVA may have different alignment. 2. For normal memory mapping, we are sure hugepage size properly fit into vma, so we don't check whether the mapping size exceeds the boundary of vma. But for device memory mapping, we should pay attention to this. This adds get_vma_page_shift() to get page shift for both normal memory and device MMIO region, and check these two points when selecting block mapping size for MMIO region. Signed-off-by: Keqian Zhu Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20210507110322.23348-3-zhukeqian1@huawei.com --- arch/arm64/kvm/mmu.c | 61 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 51 insertions(+), 10 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index e982178c8c72..5742ba765ff9 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -822,6 +822,35 @@ transparent_hugepage_adjust(struct kvm_memory_slot *memslot, return PAGE_SIZE; } +static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva) +{ + unsigned long pa; + + if (is_vm_hugetlb_page(vma) && !(vma->vm_flags & VM_PFNMAP)) + return huge_page_shift(hstate_vma(vma)); + + if (!(vma->vm_flags & VM_PFNMAP)) + return PAGE_SHIFT; + + VM_BUG_ON(is_vm_hugetlb_page(vma)); + + pa = (vma->vm_pgoff << PAGE_SHIFT) + (hva - vma->vm_start); + +#ifndef __PAGETABLE_PMD_FOLDED + if ((hva & (PUD_SIZE - 1)) == (pa & (PUD_SIZE - 1)) && + ALIGN_DOWN(hva, PUD_SIZE) >= vma->vm_start && + ALIGN(hva, PUD_SIZE) <= vma->vm_end) + return PUD_SHIFT; +#endif + + if ((hva & (PMD_SIZE - 1)) == (pa & (PMD_SIZE - 1)) && + ALIGN_DOWN(hva, PMD_SIZE) >= vma->vm_start && + ALIGN(hva, PMD_SIZE) <= vma->vm_end) + return PMD_SHIFT; + + return PAGE_SHIFT; +} + static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, struct kvm_memory_slot *memslot, unsigned long hva, unsigned long fault_status) @@ -853,7 +882,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, return -EFAULT; } - /* Let's check if we will get back a huge page backed by hugetlbfs */ + /* + * Let's check if we will get back a huge page backed by hugetlbfs, or + * get block mapping for device MMIO region. + */ mmap_read_lock(current->mm); vma = find_vma_intersection(current->mm, hva, hva + 1); if (unlikely(!vma)) { @@ -862,15 +894,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, return -EFAULT; } - if (is_vm_hugetlb_page(vma)) - vma_shift = huge_page_shift(hstate_vma(vma)); - else - vma_shift = PAGE_SHIFT; - - if (logging_active || - (vma->vm_flags & VM_PFNMAP)) { + /* + * logging_active is guaranteed to never be true for VM_PFNMAP + * memslots. + */ + if (logging_active) { force_pte = true; vma_shift = PAGE_SHIFT; + } else { + vma_shift = get_vma_page_shift(vma, hva); } switch (vma_shift) { @@ -943,8 +975,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, return -EFAULT; if (kvm_is_device_pfn(pfn)) { + /* + * If the page was identified as device early by looking at + * the VMA flags, vma_pagesize is already representing the + * largest quantity we can map. If instead it was mapped + * via gfn_to_pfn_prot(), vma_pagesize is set to PAGE_SIZE + * and must not be upgraded. + * + * In both cases, we don't let transparent_hugepage_adjust() + * change things at the last minute. + */ device = true; - force_pte = true; } else if (logging_active && !write_fault) { /* * Only actually map the page as writable if this was a write @@ -965,7 +1006,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, * If we are not forced to use page mapping, check if we are * backed by a THP and thus use block mapping if possible. */ - if (vma_pagesize == PAGE_SIZE && !force_pte) + if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) vma_pagesize = transparent_hugepage_adjust(memslot, hva, &pfn, &fault_ipa); if (writable)