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SubjectRe: [PATCH 1/2] KVM: selftests: Keep track of memslots more efficiently
On Mon, Feb 01, 2021 at 09:10:56AM +0100, Maciej S. Szmigiero wrote:
> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
>
> The KVM selftest framework was using a simple list for keeping track of
> the memslots currently in use.
> This resulted in lookups and adding a single memslot being O(n), the
> later due to linear scanning of the existing memslot set to check for
> the presence of any conflicting entries.
>
> Before this change, benchmarking high count of memslots was more or less
> impossible as pretty much all the benchmark time was spent in the
> selftest framework code.
>
> We can simply use a rbtree for keeping track of both of gfn and hva.
> We don't need an interval tree for hva here as we can't have overlapping
> memslots because we allocate a completely new memory chunk for each new
> memslot.
>
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
> ---
> tools/testing/selftests/kvm/Makefile | 2 +-
> tools/testing/selftests/kvm/lib/kvm_util.c | 141 ++++++++++++++----
> .../selftests/kvm/lib/kvm_util_internal.h | 15 +-
> tools/testing/selftests/kvm/lib/rbtree.c | 1 +
> 4 files changed, 124 insertions(+), 35 deletions(-)
> create mode 100644 tools/testing/selftests/kvm/lib/rbtree.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index fe41c6a0fa67..e7c6237d7383 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -33,7 +33,7 @@ ifeq ($(ARCH),s390)
> UNAME_M := s390x
> endif
>
> -LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/sparsebit.c lib/test_util.c lib/guest_modes.c lib/perf_test_util.c
> +LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/rbtree.c lib/sparsebit.c lib/test_util.c lib/guest_modes.c lib/perf_test_util.c
> LIBKVM_x86_64 = lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/svm.c lib/x86_64/ucall.c lib/x86_64/handlers.S
> LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c
> LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c lib/s390x/diag318_test_handler.c
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index fa5a90e6c6f0..632433dbfa25 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -195,7 +195,9 @@ struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
> TEST_ASSERT(vm != NULL, "Insufficient Memory");
>
> INIT_LIST_HEAD(&vm->vcpus);
> - INIT_LIST_HEAD(&vm->userspace_mem_regions);
> + vm->regions.gpa_tree = RB_ROOT;
> + vm->regions.hva_tree = RB_ROOT;
> + hash_init(vm->regions.slot_hash);
>
> vm->mode = mode;
> vm->type = 0;
> @@ -347,13 +349,14 @@ struct kvm_vm *vm_create_default(uint32_t vcpuid, uint64_t extra_mem_pages,
> */
> void kvm_vm_restart(struct kvm_vm *vmp, int perm)
> {
> + int ctr;
> struct userspace_mem_region *region;
>
> vm_open(vmp, perm);
> if (vmp->has_irqchip)
> vm_create_irqchip(vmp);
>
> - list_for_each_entry(region, &vmp->userspace_mem_regions, list) {
> + hash_for_each(vmp->regions.slot_hash, ctr, region, slot_node) {
> int ret = ioctl(vmp->fd, KVM_SET_USER_MEMORY_REGION, &region->region);
> TEST_ASSERT(ret == 0, "KVM_SET_USER_MEMORY_REGION IOCTL failed,\n"
> " rc: %i errno: %i\n"
> @@ -416,14 +419,21 @@ uint32_t kvm_vm_reset_dirty_ring(struct kvm_vm *vm)
> static struct userspace_mem_region *
> userspace_mem_region_find(struct kvm_vm *vm, uint64_t start, uint64_t end)
> {
> - struct userspace_mem_region *region;
> + struct rb_node *node;
>
> - list_for_each_entry(region, &vm->userspace_mem_regions, list) {
> + for (node = vm->regions.gpa_tree.rb_node; node; ) {
> + struct userspace_mem_region *region =
> + container_of(node, struct userspace_mem_region, gpa_node);
> uint64_t existing_start = region->region.guest_phys_addr;
> uint64_t existing_end = region->region.guest_phys_addr
> + region->region.memory_size - 1;
> if (start <= existing_end && end >= existing_start)
> return region;
> +
> + if (start < existing_start)
> + node = node->rb_left;
> + else
> + node = node->rb_right;
> }
>
> return NULL;
> @@ -538,11 +548,16 @@ void kvm_vm_release(struct kvm_vm *vmp)
> }
>
> static void __vm_mem_region_delete(struct kvm_vm *vm,
> - struct userspace_mem_region *region)
> + struct userspace_mem_region *region,
> + bool unlink)
> {
> int ret;
>
> - list_del(&region->list);
> + if (unlink) {
> + rb_erase(&region->gpa_node, &vm->regions.gpa_tree);
> + rb_erase(&region->hva_node, &vm->regions.hva_tree);
> + hash_del(&region->slot_node);
> + }
>
> region->region.memory_size = 0;
> ret = ioctl(vm->fd, KVM_SET_USER_MEMORY_REGION, &region->region);
> @@ -561,14 +576,16 @@ static void __vm_mem_region_delete(struct kvm_vm *vm,
> */
> void kvm_vm_free(struct kvm_vm *vmp)
> {
> - struct userspace_mem_region *region, *tmp;
> + int ctr;
> + struct hlist_node *node;
> + struct userspace_mem_region *region;
>
> if (vmp == NULL)
> return;
>
> /* Free userspace_mem_regions. */
> - list_for_each_entry_safe(region, tmp, &vmp->userspace_mem_regions, list)
> - __vm_mem_region_delete(vmp, region);
> + hash_for_each_safe(vmp->regions.slot_hash, ctr, node, region, slot_node)
> + __vm_mem_region_delete(vmp, region, false);
>
> /* Free sparsebit arrays. */
> sparsebit_free(&vmp->vpages_valid);
> @@ -650,6 +667,57 @@ int kvm_memcmp_hva_gva(void *hva, struct kvm_vm *vm, vm_vaddr_t gva, size_t len)
> return 0;
> }
>
> +static void vm_userspace_mem_region_gpa_insert(struct rb_root *gpa_tree,
> + struct userspace_mem_region *region)
> +{
> + struct rb_node **cur, *parent;
> +
> + for (cur = &gpa_tree->rb_node, parent = NULL; *cur; ) {
> + struct userspace_mem_region *cregion;
> +
> + cregion = container_of(*cur, typeof(*cregion), gpa_node);
> + parent = *cur;
> + if (region->region.guest_phys_addr <
> + cregion->region.guest_phys_addr)
> + cur = &(*cur)->rb_left;
> + else {
> + TEST_ASSERT(region->region.guest_phys_addr !=
> + cregion->region.guest_phys_addr,
> + "Duplicate GPA in region tree");
> +
> + cur = &(*cur)->rb_right;
> + }
> + }
> +
> + rb_link_node(&region->gpa_node, parent, cur);
> + rb_insert_color(&region->gpa_node, gpa_tree);
> +}
> +
> +static void vm_userspace_mem_region_hva_insert(struct rb_root *hva_tree,
> + struct userspace_mem_region *region)
> +{
> + struct rb_node **cur, *parent;
> +
> + for (cur = &hva_tree->rb_node, parent = NULL; *cur; ) {
> + struct userspace_mem_region *cregion;
> +
> + cregion = container_of(*cur, typeof(*cregion), hva_node);
> + parent = *cur;
> + if (region->host_mem < cregion->host_mem)
> + cur = &(*cur)->rb_left;
> + else {
> + TEST_ASSERT(region->host_mem !=
> + cregion->host_mem,
> + "Duplicate HVA in region tree");
> +
> + cur = &(*cur)->rb_right;
> + }
> + }
> +
> + rb_link_node(&region->hva_node, parent, cur);
> + rb_insert_color(&region->hva_node, hva_tree);
> +}
> +
> /*
> * VM Userspace Memory Region Add
> *
> @@ -714,7 +782,8 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
> (uint64_t) region->region.memory_size);
>
> /* Confirm no region with the requested slot already exists. */
> - list_for_each_entry(region, &vm->userspace_mem_regions, list) {
> + hash_for_each_possible(vm->regions.slot_hash, region, slot_node,
> + slot) {
> if (region->region.slot != slot)
> continue;
>
> @@ -794,8 +863,10 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
> ret, errno, slot, flags,
> guest_paddr, (uint64_t) region->region.memory_size);
>
> - /* Add to linked-list of memory regions. */
> - list_add(&region->list, &vm->userspace_mem_regions);
> + /* Add to quick lookup data structures */
> + vm_userspace_mem_region_gpa_insert(&vm->regions.gpa_tree, region);
> + vm_userspace_mem_region_hva_insert(&vm->regions.hva_tree, region);
> + hash_add(vm->regions.slot_hash, &region->slot_node, slot);
> }
>
> /*
> @@ -818,10 +889,10 @@ memslot2region(struct kvm_vm *vm, uint32_t memslot)
> {
> struct userspace_mem_region *region;
>
> - list_for_each_entry(region, &vm->userspace_mem_regions, list) {
> + hash_for_each_possible(vm->regions.slot_hash, region, slot_node,
> + memslot)
> if (region->region.slot == memslot)
> return region;
> - }
>
> fprintf(stderr, "No mem region with the requested slot found,\n"
> " requested slot: %u\n", memslot);
> @@ -906,7 +977,7 @@ void vm_mem_region_move(struct kvm_vm *vm, uint32_t slot, uint64_t new_gpa)
> */
> void vm_mem_region_delete(struct kvm_vm *vm, uint32_t slot)
> {
> - __vm_mem_region_delete(vm, memslot2region(vm, slot));
> + __vm_mem_region_delete(vm, memslot2region(vm, slot), true);
> }
>
> /*
> @@ -1178,16 +1249,14 @@ void *addr_gpa2hva(struct kvm_vm *vm, vm_paddr_t gpa)
> {
> struct userspace_mem_region *region;
>
> - list_for_each_entry(region, &vm->userspace_mem_regions, list) {
> - if ((gpa >= region->region.guest_phys_addr)
> - && (gpa <= (region->region.guest_phys_addr
> - + region->region.memory_size - 1)))
> - return (void *) ((uintptr_t) region->host_mem
> - + (gpa - region->region.guest_phys_addr));
> + region = userspace_mem_region_find(vm, gpa, gpa);
> + if (!region) {
> + TEST_FAIL("No vm physical memory at 0x%lx", gpa);
> + return NULL;
> }
>
> - TEST_FAIL("No vm physical memory at 0x%lx", gpa);
> - return NULL;
> + return (void *)((uintptr_t)region->host_mem
> + + (gpa - region->region.guest_phys_addr));
> }
>
> /*
> @@ -1209,15 +1278,22 @@ void *addr_gpa2hva(struct kvm_vm *vm, vm_paddr_t gpa)
> */
> vm_paddr_t addr_hva2gpa(struct kvm_vm *vm, void *hva)
> {
> - struct userspace_mem_region *region;
> + struct rb_node *node;
> +
> + for (node = vm->regions.hva_tree.rb_node; node; ) {
> + struct userspace_mem_region *region =
> + container_of(node, struct userspace_mem_region, hva_node);
> +
> + if (hva >= region->host_mem) {
> + if (hva <= (region->host_mem
> + + region->region.memory_size - 1))
> + return (vm_paddr_t)((uintptr_t)
> + region->region.guest_phys_addr
> + + (hva - (uintptr_t)region->host_mem));
>
> - list_for_each_entry(region, &vm->userspace_mem_regions, list) {
> - if ((hva >= region->host_mem)
> - && (hva <= (region->host_mem
> - + region->region.memory_size - 1)))
> - return (vm_paddr_t) ((uintptr_t)
> - region->region.guest_phys_addr
> - + (hva - (uintptr_t) region->host_mem));
> + node = node->rb_right;
> + } else
> + node = node->rb_left;
> }
>
> TEST_FAIL("No mapping to a guest physical address, hva: %p", hva);
> @@ -1743,6 +1819,7 @@ int _kvm_ioctl(struct kvm_vm *vm, unsigned long cmd, void *arg)
> */
> void vm_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent)
> {
> + int ctr;
> struct userspace_mem_region *region;
> struct vcpu *vcpu;
>
> @@ -1750,7 +1827,7 @@ void vm_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent)
> fprintf(stream, "%*sfd: %i\n", indent, "", vm->fd);
> fprintf(stream, "%*spage_size: 0x%x\n", indent, "", vm->page_size);
> fprintf(stream, "%*sMem Regions:\n", indent, "");
> - list_for_each_entry(region, &vm->userspace_mem_regions, list) {
> + hash_for_each(vm->regions.slot_hash, ctr, region, slot_node) {
> fprintf(stream, "%*sguest_phys: 0x%lx size: 0x%lx "
> "host_virt: %p\n", indent + 2, "",
> (uint64_t) region->region.guest_phys_addr,
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util_internal.h b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
> index 34465dc562d8..af310110602b 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util_internal.h
> +++ b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
> @@ -8,6 +8,9 @@
> #ifndef SELFTEST_KVM_UTIL_INTERNAL_H
> #define SELFTEST_KVM_UTIL_INTERNAL_H
>
> +#include "linux/hashtable.h"
> +#include "linux/rbtree.h"
> +
> #include "sparsebit.h"
>
> #define KVM_DEV_PATH "/dev/kvm"
> @@ -20,7 +23,9 @@ struct userspace_mem_region {
> void *host_mem;
> void *mmap_start;
> size_t mmap_size;
> - struct list_head list;
> + struct rb_node gpa_node;
> + struct rb_node hva_node;
> + struct hlist_node slot_node;
> };
>
> struct vcpu {
> @@ -33,6 +38,12 @@ struct vcpu {
> uint32_t dirty_gfns_count;
> };
>
> +struct userspace_mem_regions {
> + struct rb_root gpa_tree;
> + struct rb_root hva_tree;
> + DECLARE_HASHTABLE(slot_hash, 9);
> +};
> +
> struct kvm_vm {
> int mode;
> unsigned long type;
> @@ -45,7 +56,7 @@ struct kvm_vm {
> unsigned int va_bits;
> uint64_t max_gfn;
> struct list_head vcpus;
> - struct list_head userspace_mem_regions;
> + struct userspace_mem_regions regions;
> struct sparsebit *vpages_valid;
> struct sparsebit *vpages_mapped;
> bool has_irqchip;
> diff --git a/tools/testing/selftests/kvm/lib/rbtree.c b/tools/testing/selftests/kvm/lib/rbtree.c
> new file mode 100644
> index 000000000000..a703f0194ea3
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/rbtree.c
> @@ -0,0 +1 @@
> +#include "../../../../lib/rbtree.c"
>

We shouldn't dip into kernel code like this. We can use tools/lib/rbtree.c
though.

Besides the rbtree.c thing,

Reviewed-by: Andrew Jones <drjones@redhat.com>

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