Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v2 2/2] KVM: selftests: add a memslot-related performance
 benchmark
To:     "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Cc:     Shuah Khan <shuah@kernel.org>,
        Sean Christopherson <seanjc@google.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Igor Mammedov <imammedo@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Andrew Jones <drjones@redhat.com>, kvm@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
References: <b12749d47ee860468240cf027412c91b76dbe3db.1618253574.git.maciej.szmigiero@oracle.com>
 <8d31bb3d92bc8fa33a9756fa802ee14266ab994e.1618253574.git.maciej.szmigiero@oracle.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <e31b73ab-a42e-2870-5982-e262cda553a1@redhat.com>
Date:   Mon, 24 May 2021 13:50:23 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.8.1
MIME-Version: 1.0
In-Reply-To: <8d31bb3d92bc8fa33a9756fa802ee14266ab994e.1618253574.git.maciej.szmigiero@oracle.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 13/04/21 16:08, Maciej S. Szmigiero wrote:
> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
> 
> This benchmark contains the following tests:
> * Map test, where the host unmaps guest memory while the guest writes to
> it (maps it).
> 
> The test is designed in a way to make the unmap operation on the host
> take a negligible amount of time in comparison with the mapping
> operation in the guest.
> 
> The test area is actually split in two: the first half is being mapped
> by the guest while the second half in being unmapped by the host.
> Then a guest <-> host sync happens and the areas are reversed.
> 
> * Unmap test which is broadly similar to the above map test, but it is
> designed in an opposite way: to make the mapping operation in the guest
> take a negligible amount of time in comparison with the unmap operation
> on the host.
> This test is available in two variants: with per-page unmap operation
> or a chunked one (using 2 MiB chunk size).
> 
> * Move active area test which involves moving the last (highest gfn)
> memslot a bit back and forth on the host while the guest is
> concurrently writing around the area being moved (including over the
> moved memslot).
> 
> * Move inactive area test which is similar to the previous move active
> area test, but now guest writes all happen outside of the area being
> moved.
> 
> * Read / write test in which the guest writes to the beginning of each
> page of the test area while the host writes to the middle of each such
> page.
> Then each side checks the values the other side has written.
> This particular test is not expected to give different results depending
> on particular memslots implementation, it is meant as a rough sanity
> check and to provide insight on the spread of test results expected.
> 
> Each test performs its operation in a loop until a test period ends
> (this is 5 seconds by default, but it is configurable).
> Then the total count of loops done is divided by the actual elapsed
> time to give the test result.
> 
> The tests have a configurable memslot cap with the "-s" test option, by
> default the system maximum is used.
> Each test is repeated a particular number of times (by default 20
> times), the best result achieved is printed.
> 
> The test memory area is divided equally between memslots, the reminder
> is added to the last memslot.
> The test area size does not depend on the number of memslots in use.
> 
> The tests also measure the time that it took to add all these memslots.
> The best result from the tests that use the whole test area is printed
> after all the requested tests are done.
> 
> In general, these tests are designed to use as much memory as possible
> (within reason) while still doing 100+ loops even on high memslot counts
> with the default test length.
> Increasing the test runtime makes it increasingly more likely that some
> event will happen on the system during the test run, which might lower
> the test result.
> 
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
> Reviewed-by: Andrew Jones <drjones@redhat.com>
> ---
> 
> Changes from v1:
> * Try to keep alphabetic order when adding new entries to Makefile
>    and .gitignore
> 
> * Remove no longer necessary explicit vcpu_set_cpuid() call
> 
> * Add Andrew's Reviewed-by: tag
> 
>   tools/testing/selftests/kvm/.gitignore        |    1 +
>   tools/testing/selftests/kvm/Makefile          |    1 +
>   .../testing/selftests/kvm/memslot_perf_test.c | 1037 +++++++++++++++++
>   3 files changed, 1039 insertions(+)
>   create mode 100644 tools/testing/selftests/kvm/memslot_perf_test.c
> 
> diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
> index 32b87cc77c8e..40a36f5570ad 100644
> --- a/tools/testing/selftests/kvm/.gitignore
> +++ b/tools/testing/selftests/kvm/.gitignore
> @@ -36,5 +36,6 @@
>   /hardware_disable_test
>   /kvm_create_max_vcpus
>   /memslot_modification_stress_test
> +/memslot_perf_test
>   /set_memory_region_test
>   /steal_time
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index c30a21c1d676..401ef2e88991 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -70,6 +70,7 @@ TEST_GEN_PROGS_x86_64 += dirty_log_perf_test
>   TEST_GEN_PROGS_x86_64 += hardware_disable_test
>   TEST_GEN_PROGS_x86_64 += kvm_create_max_vcpus
>   TEST_GEN_PROGS_x86_64 += memslot_modification_stress_test
> +TEST_GEN_PROGS_x86_64 += memslot_perf_test
>   TEST_GEN_PROGS_x86_64 += set_memory_region_test
>   TEST_GEN_PROGS_x86_64 += steal_time
>   
> diff --git a/tools/testing/selftests/kvm/memslot_perf_test.c b/tools/testing/selftests/kvm/memslot_perf_test.c
> new file mode 100644
> index 000000000000..4ae0e5ec0f74
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/memslot_perf_test.c
> @@ -0,0 +1,1037 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * A memslot-related performance benchmark.
> + *
> + * Copyright (C) 2021 Oracle and/or its affiliates.
> + *
> + * Basic guest setup / host vCPU thread code lifted from set_memory_region_test.
> + */
> +#include <pthread.h>
> +#include <sched.h>
> +#include <semaphore.h>
> +#include <stdatomic.h>
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/mman.h>
> +#include <time.h>
> +#include <unistd.h>
> +
> +#include <linux/compiler.h>
> +
> +#include <test_util.h>
> +#include <kvm_util.h>
> +#include <processor.h>
> +
> +#define VCPU_ID 0
> +
> +#define MEM_SIZE		((512U << 20) + 4096)
> +#define MEM_SIZE_PAGES		(MEM_SIZE / 4096)
> +#define MEM_GPA		0x10000000UL
> +#define MEM_AUX_GPA		MEM_GPA
> +#define MEM_SYNC_GPA		MEM_AUX_GPA
> +#define MEM_TEST_GPA		(MEM_AUX_GPA + 4096)
> +#define MEM_TEST_SIZE		(MEM_SIZE - 4096)
> +static_assert(MEM_SIZE % 4096 == 0, "invalid mem size");
> +static_assert(MEM_TEST_SIZE % 4096 == 0, "invalid mem test size");
> +
> +/*
> + * 32 MiB is max size that gets well over 100 iterations on 509 slots.
> + * Considering that each slot needs to have at least one page up to
> + * 8194 slots in use can then be tested (although with slightly
> + * limited resolution).
> + */
> +#define MEM_SIZE_MAP		((32U << 20) + 4096)
> +#define MEM_SIZE_MAP_PAGES	(MEM_SIZE_MAP / 4096)
> +#define MEM_TEST_MAP_SIZE	(MEM_SIZE_MAP - 4096)
> +#define MEM_TEST_MAP_SIZE_PAGES (MEM_TEST_MAP_SIZE / 4096)
> +static_assert(MEM_SIZE_MAP % 4096 == 0, "invalid map test region size");
> +static_assert(MEM_TEST_MAP_SIZE % 4096 == 0, "invalid map test region size");
> +static_assert(MEM_TEST_MAP_SIZE_PAGES % 2 == 0, "invalid map test region size");
> +static_assert(MEM_TEST_MAP_SIZE_PAGES > 2, "invalid map test region size");
> +
> +/*
> + * 128 MiB is min size that fills 32k slots with at least one page in each
> + * while at the same time gets 100+ iterations in such test
> + */
> +#define MEM_TEST_UNMAP_SIZE		(128U << 20)
> +#define MEM_TEST_UNMAP_SIZE_PAGES	(MEM_TEST_UNMAP_SIZE / 4096)
> +/* 2 MiB chunk size like a typical huge page */
> +#define MEM_TEST_UNMAP_CHUNK_PAGES	(2U << (20 - 12))
> +static_assert(MEM_TEST_UNMAP_SIZE <= MEM_TEST_SIZE,
> +	      "invalid unmap test region size");
> +static_assert(MEM_TEST_UNMAP_SIZE % 4096 == 0,
> +	      "invalid unmap test region size");
> +static_assert(MEM_TEST_UNMAP_SIZE_PAGES %
> +	      (2 * MEM_TEST_UNMAP_CHUNK_PAGES) == 0,
> +	      "invalid unmap test region size");
> +
> +/*
> + * For the move active test the middle of the test area is placed on
> + * a memslot boundary: half lies in the memslot being moved, half in
> + * other memslot(s).
> + *
> + * When running this test with 32k memslots (32764, really) each memslot
> + * contains 4 pages.
> + * The last one additionally contains the remaining 21 pages of memory,
> + * for the total size of 25 pages.
> + * Hence, the maximum size here is 50 pages.
> + */
> +#define MEM_TEST_MOVE_SIZE_PAGES	(50)
> +#define MEM_TEST_MOVE_SIZE		(MEM_TEST_MOVE_SIZE_PAGES * 4096)
> +#define MEM_TEST_MOVE_GPA_DEST		(MEM_GPA + MEM_SIZE)
> +static_assert(MEM_TEST_MOVE_SIZE <= MEM_TEST_SIZE,
> +	      "invalid move test region size");
> +
> +#define MEM_TEST_VAL_1 0x1122334455667788
> +#define MEM_TEST_VAL_2 0x99AABBCCDDEEFF00
> +
> +struct vm_data {
> +	struct kvm_vm *vm;
> +	pthread_t vcpu_thread;
> +	uint32_t nslots;
> +	uint64_t npages;
> +	uint64_t pages_per_slot;
> +	void **hva_slots;
> +	bool mmio_ok;
> +	uint64_t mmio_gpa_min;
> +	uint64_t mmio_gpa_max;
> +};
> +
> +struct sync_area {
> +	atomic_bool start_flag;
> +	atomic_bool exit_flag;
> +	atomic_bool sync_flag;
> +	void *move_area_ptr;
> +};
> +
> +/*
> + * Technically, we need also for the atomic bool to be address-free, which
> + * is recommended, but not strictly required, by C11 for lockless
> + * implementations.
> + * However, in practice both GCC and Clang fulfill this requirement on
> + * all KVM-supported platforms.
> + */
> +static_assert(ATOMIC_BOOL_LOCK_FREE == 2, "atomic bool is not lockless");
> +
> +static sem_t vcpu_ready;
> +
> +static bool map_unmap_verify;
> +
> +static bool verbose;
> +#define pr_info_v(...)				\
> +	do {					\
> +		if (verbose)			\
> +			pr_info(__VA_ARGS__);	\
> +	} while (0)
> +
> +static void *vcpu_worker(void *data)
> +{
> +	struct vm_data *vm = data;
> +	struct kvm_run *run;
> +	struct ucall uc;
> +	uint64_t cmd;
> +
> +	run = vcpu_state(vm->vm, VCPU_ID);
> +	while (1) {
> +		vcpu_run(vm->vm, VCPU_ID);
> +
> +		if (run->exit_reason == KVM_EXIT_IO) {
> +			cmd = get_ucall(vm->vm, VCPU_ID, &uc);
> +			if (cmd != UCALL_SYNC)
> +				break;
> +
> +			sem_post(&vcpu_ready);
> +			continue;
> +		}
> +
> +		if (run->exit_reason != KVM_EXIT_MMIO)
> +			break;
> +
> +		TEST_ASSERT(vm->mmio_ok, "Unexpected mmio exit");
> +		TEST_ASSERT(run->mmio.is_write, "Unexpected mmio read");
> +		TEST_ASSERT(run->mmio.len == 8,
> +			    "Unexpected exit mmio size = %u", run->mmio.len);
> +		TEST_ASSERT(run->mmio.phys_addr >= vm->mmio_gpa_min &&
> +			    run->mmio.phys_addr <= vm->mmio_gpa_max,
> +			    "Unexpected exit mmio address = 0x%llx",
> +			    run->mmio.phys_addr);
> +	}
> +
> +	if (run->exit_reason == KVM_EXIT_IO && cmd == UCALL_ABORT)
> +		TEST_FAIL("%s at %s:%ld, val = %lu", (const char *)uc.args[0],
> +			  __FILE__, uc.args[1], uc.args[2]);
> +
> +	return NULL;
> +}
> +
> +static void wait_for_vcpu(void)
> +{
> +	struct timespec ts;
> +
> +	TEST_ASSERT(!clock_gettime(CLOCK_REALTIME, &ts),
> +		    "clock_gettime() failed: %d\n", errno);
> +
> +	ts.tv_sec += 2;
> +	TEST_ASSERT(!sem_timedwait(&vcpu_ready, &ts),
> +		    "sem_timedwait() failed: %d\n", errno);
> +}
> +
> +static void *vm_gpa2hva(struct vm_data *data, uint64_t gpa, uint64_t *rempages)
> +{
> +	uint64_t gpage, pgoffs;
> +	uint32_t slot, slotoffs;
> +	void *base;
> +
> +	TEST_ASSERT(gpa >= MEM_GPA, "Too low gpa to translate");
> +	TEST_ASSERT(gpa < MEM_GPA + data->npages * 4096,
> +		    "Too high gpa to translate");
> +	gpa -= MEM_GPA;
> +
> +	gpage = gpa / 4096;
> +	pgoffs = gpa % 4096;
> +	slot = min(gpage / data->pages_per_slot, (uint64_t)data->nslots - 1);
> +	slotoffs = gpage - (slot * data->pages_per_slot);
> +
> +	if (rempages) {
> +		uint64_t slotpages;
> +
> +		if (slot == data->nslots - 1)
> +			slotpages = data->npages - slot * data->pages_per_slot;
> +		else
> +			slotpages = data->pages_per_slot;
> +
> +		TEST_ASSERT(!pgoffs,
> +			    "Asking for remaining pages in slot but gpa not page aligned");
> +		*rempages = slotpages - slotoffs;
> +	}
> +
> +	base = data->hva_slots[slot];
> +	return (uint8_t *)base + slotoffs * 4096 + pgoffs;
> +}
> +
> +static uint64_t vm_slot2gpa(struct vm_data *data, uint32_t slot)
> +{
> +	TEST_ASSERT(slot < data->nslots, "Too high slot number");
> +
> +	return MEM_GPA + slot * data->pages_per_slot * 4096;
> +}
> +
> +static struct vm_data *alloc_vm(void)
> +{
> +	struct vm_data *data;
> +
> +	data = malloc(sizeof(*data));
> +	TEST_ASSERT(data, "malloc(vmdata) failed");
> +
> +	data->vm = NULL;
> +	data->hva_slots = NULL;
> +
> +	return data;
> +}
> +
> +static bool prepare_vm(struct vm_data *data, int nslots, uint64_t *maxslots,
> +		       void *guest_code, uint64_t mempages,
> +		       struct timespec *slot_runtime)
> +{
> +	uint32_t max_mem_slots;
> +	uint64_t rempages;
> +	uint64_t guest_addr;
> +	uint32_t slot;
> +	struct timespec tstart;
> +	struct sync_area *sync;
> +
> +	max_mem_slots = kvm_check_cap(KVM_CAP_NR_MEMSLOTS);
> +	TEST_ASSERT(max_mem_slots > 1,
> +		    "KVM_CAP_NR_MEMSLOTS should be greater than 1");
> +	TEST_ASSERT(nslots > 1 || nslots == -1,
> +		    "Slot count cap should be greater than 1");
> +	if (nslots != -1)
> +		max_mem_slots = min(max_mem_slots, (uint32_t)nslots);
> +	pr_info_v("Allowed number of memory slots: %"PRIu32"\n", max_mem_slots);
> +
> +	TEST_ASSERT(mempages > 1,
> +		    "Can't test without any memory");
> +
> +	data->npages = mempages;
> +	data->nslots = max_mem_slots - 1;
> +	data->pages_per_slot = mempages / data->nslots;
> +	if (!data->pages_per_slot) {
> +		*maxslots = mempages + 1;
> +		return false;
> +	}
> +
> +	rempages = mempages % data->nslots;
> +	data->hva_slots = malloc(sizeof(*data->hva_slots) * data->nslots);
> +	TEST_ASSERT(data->hva_slots, "malloc() fail");
> +
> +	data->vm = vm_create_default(VCPU_ID, mempages, guest_code);
> +
> +	pr_info_v("Adding slots 1..%i, each slot with %"PRIu64" pages + %"PRIu64" extra pages last\n",
> +		max_mem_slots - 1, data->pages_per_slot, rempages);
> +
> +	clock_gettime(CLOCK_MONOTONIC, &tstart);
> +	for (slot = 1, guest_addr = MEM_GPA; slot < max_mem_slots; slot++) {
> +		uint64_t npages;
> +
> +		npages = data->pages_per_slot;
> +		if (slot == max_mem_slots - 1)
> +			npages += rempages;
> +
> +		vm_userspace_mem_region_add(data->vm, VM_MEM_SRC_ANONYMOUS,
> +					    guest_addr, slot, npages,
> +					    0);
> +		guest_addr += npages * 4096;
> +	}
> +	*slot_runtime = timespec_elapsed(tstart);
> +
> +	for (slot = 0, guest_addr = MEM_GPA; slot < max_mem_slots - 1; slot++) {
> +		uint64_t npages;
> +		uint64_t gpa;
> +
> +		npages = data->pages_per_slot;
> +		if (slot == max_mem_slots - 2)
> +			npages += rempages;
> +
> +		gpa = vm_phy_pages_alloc(data->vm, npages, guest_addr,
> +					 slot + 1);
> +		TEST_ASSERT(gpa == guest_addr,
> +			    "vm_phy_pages_alloc() failed\n");
> +
> +		data->hva_slots[slot] = addr_gpa2hva(data->vm, guest_addr);
> +		memset(data->hva_slots[slot], 0, npages * 4096);
> +
> +		guest_addr += npages * 4096;
> +	}
> +
> +	virt_map(data->vm, MEM_GPA, MEM_GPA, mempages, 0);
> +
> +	sync = (typeof(sync))vm_gpa2hva(data, MEM_SYNC_GPA, NULL);
> +	atomic_init(&sync->start_flag, false);
> +	atomic_init(&sync->exit_flag, false);
> +	atomic_init(&sync->sync_flag, false);
> +
> +	data->mmio_ok = false;
> +
> +	return true;
> +}
> +
> +static void launch_vm(struct vm_data *data)
> +{
> +	pr_info_v("Launching the test VM\n");
> +
> +	pthread_create(&data->vcpu_thread, NULL, vcpu_worker, data);
> +
> +	/* Ensure the guest thread is spun up. */
> +	wait_for_vcpu();
> +}
> +
> +static void free_vm(struct vm_data *data)
> +{
> +	kvm_vm_free(data->vm);
> +	free(data->hva_slots);
> +	free(data);
> +}
> +
> +static void wait_guest_exit(struct vm_data *data)
> +{
> +	pthread_join(data->vcpu_thread, NULL);
> +}
> +
> +static void let_guest_run(struct sync_area *sync)
> +{
> +	atomic_store_explicit(&sync->start_flag, true, memory_order_release);
> +}
> +
> +static void guest_spin_until_start(void)
> +{
> +	struct sync_area *sync = (typeof(sync))MEM_SYNC_GPA;
> +
> +	while (!atomic_load_explicit(&sync->start_flag, memory_order_acquire))
> +		;
> +}
> +
> +static void make_guest_exit(struct sync_area *sync)
> +{
> +	atomic_store_explicit(&sync->exit_flag, true, memory_order_release);
> +}
> +
> +static bool _guest_should_exit(void)
> +{
> +	struct sync_area *sync = (typeof(sync))MEM_SYNC_GPA;
> +
> +	return atomic_load_explicit(&sync->exit_flag, memory_order_acquire);
> +}
> +
> +#define guest_should_exit() unlikely(_guest_should_exit())
> +
> +/*
> + * noinline so we can easily see how much time the host spends waiting
> + * for the guest.
> + * For the same reason use alarm() instead of polling clock_gettime()
> + * to implement a wait timeout.
> + */
> +static noinline void host_perform_sync(struct sync_area *sync)
> +{
> +	alarm(2);
> +
> +	atomic_store_explicit(&sync->sync_flag, true, memory_order_release);
> +	while (atomic_load_explicit(&sync->sync_flag, memory_order_acquire))
> +		;
> +
> +	alarm(0);
> +}
> +
> +static bool guest_perform_sync(void)
> +{
> +	struct sync_area *sync = (typeof(sync))MEM_SYNC_GPA;
> +	bool expected;
> +
> +	do {
> +		if (guest_should_exit())
> +			return false;
> +
> +		expected = true;
> +	} while (!atomic_compare_exchange_weak_explicit(&sync->sync_flag,
> +							&expected, false,
> +							memory_order_acq_rel,
> +							memory_order_relaxed));
> +
> +	return true;
> +}
> +
> +static void guest_code_test_memslot_move(void)
> +{
> +	struct sync_area *sync = (typeof(sync))MEM_SYNC_GPA;
> +	uintptr_t base = (typeof(base))READ_ONCE(sync->move_area_ptr);
> +
> +	GUEST_SYNC(0);
> +
> +	guest_spin_until_start();
> +
> +	while (!guest_should_exit()) {
> +		uintptr_t ptr;
> +
> +		for (ptr = base; ptr < base + MEM_TEST_MOVE_SIZE;
> +		     ptr += 4096)
> +			*(uint64_t *)ptr = MEM_TEST_VAL_1;
> +
> +		/*
> +		 * No host sync here since the MMIO exits are so expensive
> +		 * that the host would spend most of its time waiting for
> +		 * the guest and so instead of measuring memslot move
> +		 * performance we would measure the performance and
> +		 * likelihood of MMIO exits
> +		 */
> +	}
> +
> +	GUEST_DONE();
> +}
> +
> +static void guest_code_test_memslot_map(void)
> +{
> +	struct sync_area *sync = (typeof(sync))MEM_SYNC_GPA;
> +
> +	GUEST_SYNC(0);
> +
> +	guest_spin_until_start();
> +
> +	while (1) {
> +		uintptr_t ptr;
> +
> +		for (ptr = MEM_TEST_GPA;
> +		     ptr < MEM_TEST_GPA + MEM_TEST_MAP_SIZE / 2; ptr += 4096)
> +			*(uint64_t *)ptr = MEM_TEST_VAL_1;
> +
> +		if (!guest_perform_sync())
> +			break;
> +
> +		for (ptr = MEM_TEST_GPA + MEM_TEST_MAP_SIZE / 2;
> +		     ptr < MEM_TEST_GPA + MEM_TEST_MAP_SIZE; ptr += 4096)
> +			*(uint64_t *)ptr = MEM_TEST_VAL_2;
> +
> +		if (!guest_perform_sync())
> +			break;
> +	}
> +
> +	GUEST_DONE();
> +}
> +
> +static void guest_code_test_memslot_unmap(void)
> +{
> +	struct sync_area *sync = (typeof(sync))MEM_SYNC_GPA;
> +
> +	GUEST_SYNC(0);
> +
> +	guest_spin_until_start();
> +
> +	while (1) {
> +		uintptr_t ptr = MEM_TEST_GPA;
> +
> +		/*
> +		 * We can afford to access (map) just a small number of pages
> +		 * per host sync as otherwise the host will spend
> +		 * a significant amount of its time waiting for the guest
> +		 * (instead of doing unmap operations), so this will
> +		 * effectively turn this test into a map performance test.
> +		 *
> +		 * Just access a single page to be on the safe side.
> +		 */
> +		*(uint64_t *)ptr = MEM_TEST_VAL_1;
> +
> +		if (!guest_perform_sync())
> +			break;
> +
> +		ptr += MEM_TEST_UNMAP_SIZE / 2;
> +		*(uint64_t *)ptr = MEM_TEST_VAL_2;
> +
> +		if (!guest_perform_sync())
> +			break;
> +	}
> +
> +	GUEST_DONE();
> +}
> +
> +static void guest_code_test_memslot_rw(void)
> +{
> +	GUEST_SYNC(0);
> +
> +	guest_spin_until_start();
> +
> +	while (1) {
> +		uintptr_t ptr;
> +
> +		for (ptr = MEM_TEST_GPA;
> +		     ptr < MEM_TEST_GPA + MEM_TEST_SIZE; ptr += 4096)
> +			*(uint64_t *)ptr = MEM_TEST_VAL_1;
> +
> +		if (!guest_perform_sync())
> +			break;
> +
> +		for (ptr = MEM_TEST_GPA + 4096 / 2;
> +		     ptr < MEM_TEST_GPA + MEM_TEST_SIZE; ptr += 4096) {
> +			uint64_t val = *(uint64_t *)ptr;
> +
> +			GUEST_ASSERT_1(val == MEM_TEST_VAL_2, val);
> +			*(uint64_t *)ptr = 0;
> +		}
> +
> +		if (!guest_perform_sync())
> +			break;
> +	}
> +
> +	GUEST_DONE();
> +}
> +
> +static bool test_memslot_move_prepare(struct vm_data *data,
> +				      struct sync_area *sync,
> +				      uint64_t *maxslots, bool isactive)
> +{
> +	uint64_t movesrcgpa, movetestgpa;
> +
> +	movesrcgpa = vm_slot2gpa(data, data->nslots - 1);
> +
> +	if (isactive) {
> +		uint64_t lastpages;
> +
> +		vm_gpa2hva(data, movesrcgpa, &lastpages);
> +		if (lastpages < MEM_TEST_MOVE_SIZE_PAGES / 2) {
> +			*maxslots = 0;
> +			return false;
> +		}
> +	}
> +
> +	movetestgpa = movesrcgpa - (MEM_TEST_MOVE_SIZE / (isactive ? 2 : 1));
> +	sync->move_area_ptr = (void *)movetestgpa;
> +
> +	if (isactive) {
> +		data->mmio_ok = true;
> +		data->mmio_gpa_min = movesrcgpa;
> +		data->mmio_gpa_max = movesrcgpa + MEM_TEST_MOVE_SIZE / 2 - 1;
> +	}
> +
> +	return true;
> +}
> +
> +static bool test_memslot_move_prepare_active(struct vm_data *data,
> +					     struct sync_area *sync,
> +					     uint64_t *maxslots)
> +{
> +	return test_memslot_move_prepare(data, sync, maxslots, true);
> +}
> +
> +static bool test_memslot_move_prepare_inactive(struct vm_data *data,
> +					       struct sync_area *sync,
> +					       uint64_t *maxslots)
> +{
> +	return test_memslot_move_prepare(data, sync, maxslots, false);
> +}
> +
> +static void test_memslot_move_loop(struct vm_data *data, struct sync_area *sync)
> +{
> +	uint64_t movesrcgpa;
> +
> +	movesrcgpa = vm_slot2gpa(data, data->nslots - 1);
> +	vm_mem_region_move(data->vm, data->nslots - 1 + 1,
> +			   MEM_TEST_MOVE_GPA_DEST);
> +	vm_mem_region_move(data->vm, data->nslots - 1 + 1, movesrcgpa);
> +}
> +
> +static void test_memslot_do_unmap(struct vm_data *data,
> +				  uint64_t offsp, uint64_t count)
> +{
> +	uint64_t gpa, ctr;
> +
> +	for (gpa = MEM_TEST_GPA + offsp * 4096, ctr = 0; ctr < count; ) {
> +		uint64_t npages;
> +		void *hva;
> +		int ret;
> +
> +		hva = vm_gpa2hva(data, gpa, &npages);
> +		TEST_ASSERT(npages, "Empty memory slot at gptr 0x%"PRIx64, gpa);
> +		npages = min(npages, count - ctr);
> +		ret = madvise(hva, npages * 4096, MADV_DONTNEED);
> +		TEST_ASSERT(!ret,
> +			    "madvise(%p, MADV_DONTNEED) on VM memory should not fail for gptr 0x%"PRIx64,
> +			    hva, gpa);
> +		ctr += npages;
> +		gpa += npages * 4096;
> +	}
> +	TEST_ASSERT(ctr == count,
> +		    "madvise(MADV_DONTNEED) should exactly cover all of the requested area");
> +}
> +
> +static void test_memslot_map_unmap_check(struct vm_data *data,
> +					 uint64_t offsp, uint64_t valexp)
> +{
> +	uint64_t gpa;
> +	uint64_t *val;
> +
> +	if (!map_unmap_verify)
> +		return;
> +
> +	gpa = MEM_TEST_GPA + offsp * 4096;
> +	val = (typeof(val))vm_gpa2hva(data, gpa, NULL);
> +	TEST_ASSERT(*val == valexp,
> +		    "Guest written values should read back correctly before unmap (%"PRIu64" vs %"PRIu64" @ %"PRIx64")",
> +		    *val, valexp, gpa);
> +	*val = 0;
> +}
> +
> +static void test_memslot_map_loop(struct vm_data *data, struct sync_area *sync)
> +{
> +	/*
> +	 * Unmap the second half of the test area while guest writes to (maps)
> +	 * the first half.
> +	 */
> +	test_memslot_do_unmap(data, MEM_TEST_MAP_SIZE_PAGES / 2,
> +			      MEM_TEST_MAP_SIZE_PAGES / 2);
> +
> +	/*
> +	 * Wait for the guest to finish writing the first half of the test
> +	 * area, verify the written value on the first and the last page of
> +	 * this area and then unmap it.
> +	 * Meanwhile, the guest is writing to (mapping) the second half of
> +	 * the test area.
> +	 */
> +	host_perform_sync(sync);
> +	test_memslot_map_unmap_check(data, 0, MEM_TEST_VAL_1);
> +	test_memslot_map_unmap_check(data,
> +				     MEM_TEST_MAP_SIZE_PAGES / 2 - 1,
> +				     MEM_TEST_VAL_1);
> +	test_memslot_do_unmap(data, 0, MEM_TEST_MAP_SIZE_PAGES / 2);
> +
> +
> +	/*
> +	 * Wait for the guest to finish writing the second half of the test
> +	 * area and verify the written value on the first and the last page
> +	 * of this area.
> +	 * The area will be unmapped at the beginning of the next loop
> +	 * iteration.
> +	 * Meanwhile, the guest is writing to (mapping) the first half of
> +	 * the test area.
> +	 */
> +	host_perform_sync(sync);
> +	test_memslot_map_unmap_check(data, MEM_TEST_MAP_SIZE_PAGES / 2,
> +				     MEM_TEST_VAL_2);
> +	test_memslot_map_unmap_check(data, MEM_TEST_MAP_SIZE_PAGES - 1,
> +				     MEM_TEST_VAL_2);
> +}
> +
> +static void test_memslot_unmap_loop_common(struct vm_data *data,
> +					   struct sync_area *sync,
> +					   uint64_t chunk)
> +{
> +	uint64_t ctr;
> +
> +	/*
> +	 * Wait for the guest to finish mapping page(s) in the first half
> +	 * of the test area, verify the written value and then perform unmap
> +	 * of this area.
> +	 * Meanwhile, the guest is writing to (mapping) page(s) in the second
> +	 * half of the test area.
> +	 */
> +	host_perform_sync(sync);
> +	test_memslot_map_unmap_check(data, 0, MEM_TEST_VAL_1);
> +	for (ctr = 0; ctr < MEM_TEST_UNMAP_SIZE_PAGES / 2; ctr += chunk)
> +		test_memslot_do_unmap(data, ctr, chunk);
> +
> +	/* Likewise, but for the opposite host / guest areas */
> +	host_perform_sync(sync);
> +	test_memslot_map_unmap_check(data, MEM_TEST_UNMAP_SIZE_PAGES / 2,
> +				     MEM_TEST_VAL_2);
> +	for (ctr = MEM_TEST_UNMAP_SIZE_PAGES / 2;
> +	     ctr < MEM_TEST_UNMAP_SIZE_PAGES; ctr += chunk)
> +		test_memslot_do_unmap(data, ctr, chunk);
> +}
> +
> +static void test_memslot_unmap_loop(struct vm_data *data,
> +				    struct sync_area *sync)
> +{
> +	test_memslot_unmap_loop_common(data, sync, 1);
> +}
> +
> +static void test_memslot_unmap_loop_chunked(struct vm_data *data,
> +					    struct sync_area *sync)
> +{
> +	test_memslot_unmap_loop_common(data, sync, MEM_TEST_UNMAP_CHUNK_PAGES);
> +}
> +
> +static void test_memslot_rw_loop(struct vm_data *data, struct sync_area *sync)
> +{
> +	uint64_t gptr;
> +
> +	for (gptr = MEM_TEST_GPA + 4096 / 2;
> +	     gptr < MEM_TEST_GPA + MEM_TEST_SIZE; gptr += 4096)
> +		*(uint64_t *)vm_gpa2hva(data, gptr, NULL) = MEM_TEST_VAL_2;
> +
> +	host_perform_sync(sync);
> +
> +	for (gptr = MEM_TEST_GPA;
> +	     gptr < MEM_TEST_GPA + MEM_TEST_SIZE; gptr += 4096) {
> +		uint64_t *vptr = (typeof(vptr))vm_gpa2hva(data, gptr, NULL);
> +		uint64_t val = *vptr;
> +
> +		TEST_ASSERT(val == MEM_TEST_VAL_1,
> +			    "Guest written values should read back correctly (is %"PRIu64" @ %"PRIx64")",
> +			    val, gptr);
> +		*vptr = 0;
> +	}
> +
> +	host_perform_sync(sync);
> +}
> +
> +struct test_data {
> +	const char *name;
> +	uint64_t mem_size;
> +	void (*guest_code)(void);
> +	bool (*prepare)(struct vm_data *data, struct sync_area *sync,
> +			uint64_t *maxslots);
> +	void (*loop)(struct vm_data *data, struct sync_area *sync);
> +};
> +
> +static bool test_execute(int nslots, uint64_t *maxslots,
> +			 unsigned int maxtime,
> +			 const struct test_data *tdata,
> +			 uint64_t *nloops,
> +			 struct timespec *slot_runtime,
> +			 struct timespec *guest_runtime)
> +{
> +	uint64_t mem_size = tdata->mem_size ? : MEM_SIZE_PAGES;
> +	struct vm_data *data;
> +	struct sync_area *sync;
> +	struct timespec tstart;
> +	bool ret = true;
> +
> +	data = alloc_vm();
> +	if (!prepare_vm(data, nslots, maxslots, tdata->guest_code,
> +			mem_size, slot_runtime)) {
> +		ret = false;
> +		goto exit_free;
> +	}
> +
> +	sync = (typeof(sync))vm_gpa2hva(data, MEM_SYNC_GPA, NULL);
> +
> +	if (tdata->prepare &&
> +	    !tdata->prepare(data, sync, maxslots)) {
> +		ret = false;
> +		goto exit_free;
> +	}
> +
> +	launch_vm(data);
> +
> +	clock_gettime(CLOCK_MONOTONIC, &tstart);
> +	let_guest_run(sync);
> +
> +	while (1) {
> +		*guest_runtime = timespec_elapsed(tstart);
> +		if (guest_runtime->tv_sec >= maxtime)
> +			break;
> +
> +		tdata->loop(data, sync);
> +
> +		(*nloops)++;
> +	}
> +
> +	make_guest_exit(sync);
> +	wait_guest_exit(data);
> +
> +exit_free:
> +	free_vm(data);
> +
> +	return ret;
> +}
> +
> +static const struct test_data tests[] = {
> +	{
> +		.name = "map",
> +		.mem_size = MEM_SIZE_MAP_PAGES,
> +		.guest_code = guest_code_test_memslot_map,
> +		.loop = test_memslot_map_loop,
> +	},
> +	{
> +		.name = "unmap",
> +		.mem_size = MEM_TEST_UNMAP_SIZE_PAGES + 1,
> +		.guest_code = guest_code_test_memslot_unmap,
> +		.loop = test_memslot_unmap_loop,
> +	},
> +	{
> +		.name = "unmap chunked",
> +		.mem_size = MEM_TEST_UNMAP_SIZE_PAGES + 1,
> +		.guest_code = guest_code_test_memslot_unmap,
> +		.loop = test_memslot_unmap_loop_chunked,
> +	},
> +	{
> +		.name = "move active area",
> +		.guest_code = guest_code_test_memslot_move,
> +		.prepare = test_memslot_move_prepare_active,
> +		.loop = test_memslot_move_loop,
> +	},
> +	{
> +		.name = "move inactive area",
> +		.guest_code = guest_code_test_memslot_move,
> +		.prepare = test_memslot_move_prepare_inactive,
> +		.loop = test_memslot_move_loop,
> +	},
> +	{
> +		.name = "RW",
> +		.guest_code = guest_code_test_memslot_rw,
> +		.loop = test_memslot_rw_loop
> +	},
> +};
> +
> +#define NTESTS ARRAY_SIZE(tests)
> +
> +struct test_args {
> +	int tfirst;
> +	int tlast;
> +	int nslots;
> +	int seconds;
> +	int runs;
> +};
> +
> +static void help(char *name, struct test_args *targs)
> +{
> +	int ctr;
> +
> +	pr_info("usage: %s [-h] [-v] [-d] [-s slots] [-f first_test] [-e last_test] [-l test_length] [-r run_count]\n",
> +		name);
> +	pr_info(" -h: print this help screen.\n");
> +	pr_info(" -v: enable verbose mode (not for benchmarking).\n");
> +	pr_info(" -d: enable extra debug checks.\n");
> +	pr_info(" -s: specify memslot count cap (-1 means no cap; currently: %i)\n",
> +		targs->nslots);
> +	pr_info(" -f: specify the first test to run (currently: %i; max %zu)\n",
> +		targs->tfirst, NTESTS - 1);
> +	pr_info(" -e: specify the last test to run (currently: %i; max %zu)\n",
> +		targs->tlast, NTESTS - 1);
> +	pr_info(" -l: specify the test length in seconds (currently: %i)\n",
> +		targs->seconds);
> +	pr_info(" -r: specify the number of runs per test (currently: %i)\n",
> +		targs->runs);
> +
> +	pr_info("\nAvailable tests:\n");
> +	for (ctr = 0; ctr < NTESTS; ctr++)
> +		pr_info("%d: %s\n", ctr, tests[ctr].name);
> +}
> +
> +static bool parse_args(int argc, char *argv[],
> +		       struct test_args *targs)
> +{
> +	int opt;
> +
> +	while ((opt = getopt(argc, argv, "hvds:f:e:l:r:")) != -1) {
> +		switch (opt) {
> +		case 'h':
> +		default:
> +			help(argv[0], targs);
> +			return false;
> +		case 'v':
> +			verbose = true;
> +			break;
> +		case 'd':
> +			map_unmap_verify = true;
> +			break;
> +		case 's':
> +			targs->nslots = atoi(optarg);
> +			if (targs->nslots <= 0 && targs->nslots != -1) {
> +				pr_info("Slot count cap has to be positive or -1 for no cap\n");
> +				return false;
> +			}
> +			break;
> +		case 'f':
> +			targs->tfirst = atoi(optarg);
> +			if (targs->tfirst < 0) {
> +				pr_info("First test to run has to be non-negative\n");
> +				return false;
> +			}
> +			break;
> +		case 'e':
> +			targs->tlast = atoi(optarg);
> +			if (targs->tlast < 0 || targs->tlast >= NTESTS) {
> +				pr_info("Last test to run has to be non-negative and less than %zu\n",
> +					NTESTS);
> +				return false;
> +			}
> +			break;
> +		case 'l':
> +			targs->seconds = atoi(optarg);
> +			if (targs->seconds < 0) {
> +				pr_info("Test length in seconds has to be non-negative\n");
> +				return false;
> +			}
> +			break;
> +		case 'r':
> +			targs->runs = atoi(optarg);
> +			if (targs->runs <= 0) {
> +				pr_info("Runs per test has to be positive\n");
> +				return false;
> +			}
> +			break;
> +		}
> +	}
> +
> +	if (optind < argc) {
> +		help(argv[0], targs);
> +		return false;
> +	}
> +
> +	if (targs->tfirst > targs->tlast) {
> +		pr_info("First test to run cannot be greater than the last test to run\n");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +struct test_result {
> +	struct timespec slot_runtime, guest_runtime, iter_runtime;
> +	int64_t slottimens, runtimens;
> +	uint64_t nloops;
> +};
> +
> +static bool test_loop(const struct test_data *data,
> +		      const struct test_args *targs,
> +		      struct test_result *rbestslottime,
> +		      struct test_result *rbestruntime)
> +{
> +	uint64_t maxslots;
> +	struct test_result result;
> +
> +	result.nloops = 0;
> +	if (!test_execute(targs->nslots, &maxslots, targs->seconds, data,
> +			  &result.nloops,
> +			  &result.slot_runtime, &result.guest_runtime)) {
> +		if (maxslots)
> +			pr_info("Memslot count too high for this test, decrease the cap (max is %"PRIu64")\n",
> +				maxslots);
> +		else
> +			pr_info("Memslot count may be too high for this test, try adjusting the cap\n");
> +
> +		return false;
> +	}
> +
> +	pr_info("Test took %ld.%.9lds for slot setup + %ld.%.9lds all iterations\n",
> +		result.slot_runtime.tv_sec, result.slot_runtime.tv_nsec,
> +		result.guest_runtime.tv_sec, result.guest_runtime.tv_nsec);
> +	if (!result.nloops) {
> +		pr_info("No full loops done - too short test time or system too loaded?\n");
> +		return true;
> +	}
> +
> +	result.iter_runtime = timespec_div(result.guest_runtime,
> +					   result.nloops);
> +	pr_info("Done %"PRIu64" iterations, avg %ld.%.9lds each\n",
> +		result.nloops,
> +		result.iter_runtime.tv_sec,
> +		result.iter_runtime.tv_nsec);
> +	result.slottimens = timespec_to_ns(result.slot_runtime);
> +	result.runtimens = timespec_to_ns(result.iter_runtime);
> +
> +	/*
> +	 * Only rank the slot setup time for tests using the whole test memory
> +	 * area so they are comparable
> +	 */
> +	if (!data->mem_size &&
> +	    (!rbestslottime->slottimens ||
> +	     result.slottimens < rbestslottime->slottimens))
> +		*rbestslottime = result;
> +	if (!rbestruntime->runtimens ||
> +	    result.runtimens < rbestruntime->runtimens)
> +		*rbestruntime = result;
> +
> +	return true;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	struct test_args targs = {
> +		.tfirst = 0,
> +		.tlast = NTESTS - 1,
> +		.nslots = -1,
> +		.seconds = 5,
> +		.runs = 20,
> +	};
> +	struct test_result rbestslottime;
> +	int tctr;
> +
> +	/* Tell stdout not to buffer its content */
> +	setbuf(stdout, NULL);
> +
> +	if (!parse_args(argc, argv, &targs))
> +		return -1;
> +
> +	rbestslottime.slottimens = 0;
> +	for (tctr = targs.tfirst; tctr <= targs.tlast; tctr++) {
> +		const struct test_data *data = &tests[tctr];
> +		unsigned int runctr;
> +		struct test_result rbestruntime;
> +
> +		if (tctr > targs.tfirst)
> +			pr_info("\n");
> +
> +		pr_info("Testing %s performance with %i runs, %d seconds each\n",
> +			data->name, targs.runs, targs.seconds);
> +
> +		rbestruntime.runtimens = 0;
> +		for (runctr = 0; runctr < targs.runs; runctr++)
> +			if (!test_loop(data, &targs,
> +				       &rbestslottime, &rbestruntime))
> +				break;
> +
> +		if (rbestruntime.runtimens)
> +			pr_info("Best runtime result was %ld.%.9lds per iteration (with %"PRIu64" iterations)\n",
> +				rbestruntime.iter_runtime.tv_sec,
> +				rbestruntime.iter_runtime.tv_nsec,
> +				rbestruntime.nloops);
> +	}
> +
> +	if (rbestslottime.slottimens)
> +		pr_info("Best slot setup time for the whole test area was %ld.%.9lds\n",
> +			rbestslottime.slot_runtime.tv_sec,
> +			rbestslottime.slot_runtime.tv_nsec);
> +
> +	return 0;
> +}
> 

Queued both, thanks.

Paolo