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Date:   Mon, 28 Mar 2022 18:57:12 +0000
From:   David Matlack <dmatlack@google.com>
To:     Ben Gardon <bgardon@google.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>,
        Peter Xu <peterx@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Jim Mattson <jmattson@google.com>,
        David Dunn <daviddunn@google.com>,
        Jing Zhang <jingzhangos@google.com>,
        Junaid Shahid <junaids@google.com>
Subject: Re: [PATCH v2 06/11] KVM: selftests: Add NX huge pages test
Message-ID: <YkIFCHFBOy+VIllw@google.com>
References: <20220321234844.1543161-1-bgardon@google.com>
 <20220321234844.1543161-7-bgardon@google.com>
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On Mon, Mar 21, 2022 at 04:48:39PM -0700, Ben Gardon wrote:
> There's currently no test coverage of NX hugepages in KVM selftests, so
> add a basic test to ensure that the feature works as intended.
> 
> Reviewed-by: David Dunn <daviddunn@google.com>
> 
> Signed-off-by: Ben Gardon <bgardon@google.com>
> ---
>  tools/testing/selftests/kvm/Makefile          |   3 +-
>  .../kvm/lib/x86_64/nx_huge_pages_guest.S      |  45 ++++++
>  .../selftests/kvm/x86_64/nx_huge_pages_test.c | 133 ++++++++++++++++++
>  .../kvm/x86_64/nx_huge_pages_test.sh          |  25 ++++
>  4 files changed, 205 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/kvm/lib/x86_64/nx_huge_pages_guest.S
>  create mode 100644 tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
>  create mode 100755 tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> 
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 04099f453b59..6ee30c0df323 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -38,7 +38,7 @@ ifeq ($(ARCH),riscv)
>  endif
>  
>  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/apic.c 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_x86_64 = lib/x86_64/apic.c 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 lib/x86_64/nx_huge_pages_guest.S
>  LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c lib/aarch64/handlers.S lib/aarch64/spinlock.c lib/aarch64/gic.c lib/aarch64/gic_v3.c lib/aarch64/vgic.c
>  LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c lib/s390x/diag318_test_handler.c
>  LIBKVM_riscv = lib/riscv/processor.c lib/riscv/ucall.c
> @@ -56,6 +56,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/kvm_clock_test
>  TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
>  TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
>  TEST_GEN_PROGS_x86_64 += x86_64/mmu_role_test
> +TEST_GEN_PROGS_x86_64 += x86_64/nx_huge_pages_test

This will make the selftest infrastructure treat nx_huge_pages_test as
the selftest that gets run by default (e.g. if someone runs `make
kselftest`). But you actually want nx_huge_pages_test.sh to be the
selftest that gets run (nx_huge_pages_test is really just a helper
binary). Is that correct?

Take a look at [1] for how to set this up. Specifically I think you want
to move nx_huge_pages_test to TEST_GEN_PROGS_EXTENDED and add
nx_huge_pages_test.sh to TEST_PROGS.

I'd love to have the infrastructure in place for doing this because I've
been wanting to add some shell script wrappers for dirty_log_perf_test
to set up HugeTLBFS and invoke it with various different arguments.

[1] https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html#contributing-new-tests-details

>  TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
>  TEST_GEN_PROGS_x86_64 += x86_64/pmu_event_filter_test
>  TEST_GEN_PROGS_x86_64 += x86_64/set_boot_cpu_id
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/nx_huge_pages_guest.S b/tools/testing/selftests/kvm/lib/x86_64/nx_huge_pages_guest.S
> new file mode 100644
> index 000000000000..09c66b9562a3
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/x86_64/nx_huge_pages_guest.S
> @@ -0,0 +1,45 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * tools/testing/selftests/kvm/nx_huge_page_guest.S
> + *
> + * Copyright (C) 2022, Google LLC.
> + */
> +
> +.include "kvm_util.h"
> +
> +#define HPAGE_SIZE 	(2*1024*1024)
> +#define PORT_SUCCESS	0x70
> +
> +.global guest_code0
> +.global guest_code1
> +
> +.align HPAGE_SIZE
> +exit_vm:
> +	mov    $0x1,%edi
> +	mov    $0x2,%esi
> +	mov    a_string,%edx
> +	mov    $0x1,%ecx
> +	xor    %eax,%eax
> +	jmp    ucall
> +
> +
> +guest_code0:
> +	mov data1, %eax
> +	mov data2, %eax
> +	jmp exit_vm
> +
> +.align HPAGE_SIZE
> +guest_code1:
> +	mov data1, %eax
> +	mov data2, %eax
> +	jmp exit_vm
> +data1:
> +.quad	0
> +
> +.align HPAGE_SIZE
> +data2:
> +.quad	0
> +a_string:
> +.string "why does the ucall function take a string argument?"
> +
> +
> diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
> new file mode 100644
> index 000000000000..2bcbe4efdc6a
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.c
> @@ -0,0 +1,133 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * tools/testing/selftests/kvm/nx_huge_page_test.c
> + *
> + * Usage: to be run via nx_huge_page_test.sh, which does the necessary
> + * environment setup and teardown
> + *
> + * Copyright (C) 2022, Google LLC.
> + */
> +
> +#define _GNU_SOURCE
> +
> +#include <fcntl.h>
> +#include <stdint.h>
> +#include <time.h>
> +
> +#include <test_util.h>
> +#include "kvm_util.h"
> +
> +#define HPAGE_SLOT		10
> +#define HPAGE_PADDR_START       (10*1024*1024)
> +#define HPAGE_SLOT_NPAGES	(100*1024*1024/4096)
> +
> +/* Defined in nx_huge_page_guest.S */
> +void guest_code0(void);
> +void guest_code1(void);
> +
> +static void run_guest_code(struct kvm_vm *vm, void (*guest_code)(void))
> +{
> +	struct kvm_regs regs;
> +
> +	vcpu_regs_get(vm, 0, &regs);
> +	regs.rip = (uint64_t)guest_code;
> +	vcpu_regs_set(vm, 0, &regs);
> +	vcpu_run(vm, 0);
> +}
> +
> +static void check_2m_page_count(struct kvm_vm *vm, int expected_pages_2m)
> +{
> +	int actual_pages_2m;
> +
> +	actual_pages_2m = vm_get_single_stat(vm, "pages_2m");
> +
> +	TEST_ASSERT(actual_pages_2m == expected_pages_2m,
> +		    "Unexpected 2m page count. Expected %d, got %d",
> +		    expected_pages_2m, actual_pages_2m);
> +}
> +
> +static void check_split_count(struct kvm_vm *vm, int expected_splits)
> +{
> +	int actual_splits;
> +
> +	actual_splits = vm_get_single_stat(vm, "nx_lpage_splits");
> +
> +	TEST_ASSERT(actual_splits == expected_splits,
> +		    "Unexpected nx lpage split count. Expected %d, got %d",
> +		    expected_splits, actual_splits);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	struct kvm_vm *vm;
> +	struct timespec ts;
> +
> +	vm = vm_create(VM_MODE_DEFAULT, DEFAULT_GUEST_PHY_PAGES, O_RDWR);
> +
> +	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS_HUGETLB,
> +				    HPAGE_PADDR_START, HPAGE_SLOT,
> +				    HPAGE_SLOT_NPAGES, 0);
> +
> +	kvm_vm_elf_load_memslot(vm, program_invocation_name, HPAGE_SLOT);
> +
> +	vm_vcpu_add_default(vm, 0, guest_code0);
> +
> +	check_2m_page_count(vm, 0);
> +	check_split_count(vm, 0);
> +
> +	/*
> +	 * Running guest_code0 will access data1 and data2.
> +	 * This should result in part of the huge page containing guest_code0,
> +	 * and part of the hugepage containing the ucall function being mapped
> +	 * at 4K. The huge pages containing data1 and data2 will be mapped
> +	 * at 2M.
> +	 */
> +	run_guest_code(vm, guest_code0);
> +	check_2m_page_count(vm, 2);
> +	check_split_count(vm, 2);
> +
> +	/*
> +	 * guest_code1 is in the same huge page as data1, so it will cause
> +	 * that huge page to be remapped at 4k.
> +	 */
> +	run_guest_code(vm, guest_code1);
> +	check_2m_page_count(vm, 1);
> +	check_split_count(vm, 3);
> +
> +	/* Run guest_code0 again to check that is has no effect. */
> +	run_guest_code(vm, guest_code0);
> +	check_2m_page_count(vm, 1);
> +	check_split_count(vm, 3);
> +
> +	/*
> +	 * Give recovery thread time to run. The wrapper script sets
> +	 * recovery_period_ms to 100, so wait 1.5x that.
> +	 */
> +	ts.tv_sec = 0;
> +	ts.tv_nsec = 150000000;
> +	nanosleep(&ts, NULL);
> +
> +	/*
> +	 * Now that the reclaimer has run, all the split pages should be gone.
> +	 */
> +	check_2m_page_count(vm, 1);
> +	check_split_count(vm, 0);
> +
> +	/*
> +	 * The split 2M pages should have been reclaimed, so run guest_code0
> +	 * again to check that pages are mapped at 2M again.
> +	 */
> +	run_guest_code(vm, guest_code0);
> +	check_2m_page_count(vm, 2);
> +	check_split_count(vm, 2);
> +
> +	/* Pages are once again split from running guest_code1. */
> +	run_guest_code(vm, guest_code1);
> +	check_2m_page_count(vm, 1);
> +	check_split_count(vm, 3);
> +
> +	kvm_vm_free(vm);
> +
> +	return 0;
> +}
> +
> diff --git a/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> new file mode 100755
> index 000000000000..19fc95723fcb
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/nx_huge_pages_test.sh
> @@ -0,0 +1,25 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-2.0-only */
> +
> +# tools/testing/selftests/kvm/nx_huge_page_test.sh
> +# Copyright (C) 2022, Google LLC.
> +
> +NX_HUGE_PAGES=$(cat /sys/module/kvm/parameters/nx_huge_pages)
> +NX_HUGE_PAGES_RECOVERY_RATIO=$(cat /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio)
> +NX_HUGE_PAGES_RECOVERY_PERIOD=$(cat /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms)
> +HUGE_PAGES=$(cat /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages)
> +
> +echo 1 > /sys/module/kvm/parameters/nx_huge_pages
> +echo 1 > /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio
> +echo 100 > /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms
> +echo 200 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> +
> +./nx_huge_pages_test
> +RET=$?
> +
> +echo $NX_HUGE_PAGES > /sys/module/kvm/parameters/nx_huge_pages
> +echo $NX_HUGE_PAGES_RECOVERY_RATIO > /sys/module/kvm/parameters/nx_huge_pages_recovery_ratio
> +echo $NX_HUGE_PAGES_RECOVERY_PERIOD > /sys/module/kvm/parameters/nx_huge_pages_recovery_period_ms
> +echo $HUGE_PAGES > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> +
> +exit $RET
> -- 
> 2.35.1.894.gb6a874cedc-goog
>