diff options
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 27 | ||||
| -rw-r--r-- | arch/arm64/include/asm/kvm_host.h | 15 | ||||
| -rw-r--r-- | arch/arm64/include/asm/kvm_pgtable.h | 18 | ||||
| -rw-r--r-- | arch/arm64/kvm/arm.c | 28 | ||||
| -rw-r--r-- | arch/arm64/kvm/mmu.c | 4 | ||||
| -rw-r--r-- | include/uapi/linux/kvm.h | 2 |
6 files changed, 94 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index add067793b90..656bd293c8f4 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -8445,6 +8445,33 @@ structure. When getting the Modified Change Topology Report value, the attr->addr must point to a byte where the value will be stored or retrieved from. +8.40 KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +--------------------------------------- + +:Capability: KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE +:Architectures: arm64 +:Type: vm +:Parameters: arg[0] is the new split chunk size. +:Returns: 0 on success, -EINVAL if any memslot was already created. + +This capability sets the chunk size used in Eager Page Splitting. + +Eager Page Splitting improves the performance of dirty-logging (used +in live migrations) when guest memory is backed by huge-pages. It +avoids splitting huge-pages (into PAGE_SIZE pages) on fault, by doing +it eagerly when enabling dirty logging (with the +KVM_MEM_LOG_DIRTY_PAGES flag for a memory region), or when using +KVM_CLEAR_DIRTY_LOG. + +The chunk size specifies how many pages to break at a time, using a +single allocation for each chunk. Bigger the chunk size, more pages +need to be allocated ahead of time. + +The chunk size needs to be a valid block size. The list of acceptable +block sizes is exposed in KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES as a +64-bit bitmap (each bit describing a block size). The default value is +0, to disable the eager page splitting. + 9. Known KVM API problems ========================= diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 7e7e19ef6993..b743198450b3 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -159,6 +159,21 @@ struct kvm_s2_mmu { /* The last vcpu id that ran on each physical CPU */ int __percpu *last_vcpu_ran; +#define KVM_ARM_EAGER_SPLIT_CHUNK_SIZE_DEFAULT 0 + /* + * Memory cache used to split + * KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE worth of huge pages. It + * is used to allocate stage2 page tables while splitting huge + * pages. The choice of KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE + * influences both the capacity of the split page cache, and + * how often KVM reschedules. Be wary of raising CHUNK_SIZE + * too high. + * + * Protected by kvm->slots_lock. + */ + struct kvm_mmu_memory_cache split_page_cache; + uint64_t split_page_chunk_size; + struct kvm_arch *arch; }; diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index c8e0e7d9303b..cbc6971e2cb4 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -92,6 +92,24 @@ static inline bool kvm_level_supports_block_mapping(u32 level) return level >= KVM_PGTABLE_MIN_BLOCK_LEVEL; } +static inline u32 kvm_supported_block_sizes(void) +{ + u32 level = KVM_PGTABLE_MIN_BLOCK_LEVEL; + u32 r = 0; + + for (; level < KVM_PGTABLE_MAX_LEVELS; level++) + r |= BIT(kvm_granule_shift(level)); + + return r; +} + +static inline bool kvm_is_block_size_supported(u64 size) +{ + bool is_power_of_two = IS_ALIGNED(size, size); + + return is_power_of_two && (size & kvm_supported_block_sizes()); +} + /** * struct kvm_pgtable_mm_ops - Memory management callbacks. * @zalloc_page: Allocate a single zeroed memory page. diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 14391826241c..c605626801c4 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -65,6 +65,7 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) { int r; + u64 new_cap; if (cap->flags) return -EINVAL; @@ -89,6 +90,24 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, r = 0; set_bit(KVM_ARCH_FLAG_SYSTEM_SUSPEND_ENABLED, &kvm->arch.flags); break; + case KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE: + new_cap = cap->args[0]; + + mutex_lock(&kvm->slots_lock); + /* + * To keep things simple, allow changing the chunk + * size only when no memory slots have been created. + */ + if (!kvm_are_all_memslots_empty(kvm)) { + r = -EINVAL; + } else if (new_cap && !kvm_is_block_size_supported(new_cap)) { + r = -EINVAL; + } else { + r = 0; + kvm->arch.mmu.split_page_chunk_size = new_cap; + } + mutex_unlock(&kvm->slots_lock); + break; default: r = -EINVAL; break; @@ -302,6 +321,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_ARM_PTRAUTH_GENERIC: r = system_has_full_ptr_auth(); break; + case KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE: + if (kvm) + r = kvm->arch.mmu.split_page_chunk_size; + else + r = KVM_ARM_EAGER_SPLIT_CHUNK_SIZE_DEFAULT; + break; + case KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES: + r = kvm_supported_block_sizes(); + break; default: r = 0; } diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index a0d3c773af99..f2d30486f755 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -775,6 +775,10 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t for_each_possible_cpu(cpu) *per_cpu_ptr(mmu->last_vcpu_ran, cpu) = -1; + /* The eager page splitting is disabled by default */ + mmu->split_page_chunk_size = KVM_ARM_EAGER_SPLIT_CHUNK_SIZE_DEFAULT; + mmu->split_page_cache.gfp_zero = __GFP_ZERO; + mmu->pgt = pgt; mmu->pgd_phys = __pa(pgt->pgd); return 0; diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 737318b1c1d9..44edee0211fb 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1190,6 +1190,8 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP 225 #define KVM_CAP_PMU_EVENT_MASKED_EVENTS 226 #define KVM_CAP_COUNTER_OFFSET 227 +#define KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE 228 +#define KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES 229 #ifdef KVM_CAP_IRQ_ROUTING |