Re: [PATCH v3] selftests/vm: Only run 128TBswitch with 5-level paging

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

Adam Sindelar <adam@wowsignal.io> writes:

> The test va_128TBswitch.c expects to be able to pass mmap an address hint
> and length that cross the address 1<<47. This is not possible without
> 5-level page tables, so the test fails.
>
> The test is already only run on 64-bit powerpc and x86 archs, but this
> patch adds an additional check that skips the test if PG_TABLE_LEVELS < 5.
> There is precedent for checking /proc/config.gz in selftests, e.g. in
> selftests/firmware.
>
> Running the tests produces the desired output:
>
> sudo make -C tools/testing/selftests TARGETS=vm run_tests
> ---------------------------
> running ./va_128TBswitch.sh
> ---------------------------
> ./va_128TBswitch.sh: PG_TABLE_LEVELS=4, must be >= 5 to run this test
> [SKIP]
> -------------------------------
>
> Signed-off-by: Adam Sindelar <adam@wowsignal.io>
> ---
> V2 -> V3: Clean up the commit message
> V1 -> V2: Variables local, fixed Makefile typo, comment on gzip usage
>
>  tools/testing/selftests/vm/Makefile          |  1 +
>  tools/testing/selftests/vm/run_vmtests.sh    |  2 +-
>  tools/testing/selftests/vm/va_128TBswitch.sh | 39 ++++++++++++++++++++
>  3 files changed, 41 insertions(+), 1 deletion(-)
>  create mode 100755 tools/testing/selftests/vm/va_128TBswitch.sh
>
> diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
> index c45e535ff4b8..7860d0969888 100644
> --- a/tools/testing/selftests/vm/Makefile
> +++ b/tools/testing/selftests/vm/Makefile
> @@ -91,6 +91,7 @@ endif
>  TEST_PROGS := run_vmtests.sh
>  
>  TEST_FILES := test_vmalloc.sh
> +TEST_FILES += va_128TBswitch.sh
>  
>  KSFT_KHDR_INSTALL := 1
>  include ../lib.mk
> diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
> index a2302b5faaf2..edda7350ccca 100755
> --- a/tools/testing/selftests/vm/run_vmtests.sh
> +++ b/tools/testing/selftests/vm/run_vmtests.sh
> @@ -149,7 +149,7 @@ if [ $VADDR64 -ne 0 ]; then
>  	run_test ./virtual_address_range
>  
>  	# virtual address 128TB switch test
> -	run_test ./va_128TBswitch
> +	run_test ./va_128TBswitch.sh
>  fi # VADDR64
>  
>  # vmalloc stability smoke test
> diff --git a/tools/testing/selftests/vm/va_128TBswitch.sh b/tools/testing/selftests/vm/va_128TBswitch.sh
> new file mode 100755
> index 000000000000..767a6465b5d2
> --- /dev/null
> +++ b/tools/testing/selftests/vm/va_128TBswitch.sh
> @@ -0,0 +1,39 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Copyright (C) 2022 Adam Sindelar (Meta) <adam@wowsignal.io>
> +#
> +# This is a test for mmap behavior with 5-level paging. This script wraps the
> +# real test to check that the kernel is configured to support at least 5
> +# pagetable levels.
> +
> +# 1 means the test failed
> +exitcode=1
> +
> +# Kselftest framework requirement - SKIP code is 4.
> +ksft_skip=4
> +
> +die()
> +{
> +    echo "$1"
> +    exit $exitcode
> +}
> +
> +check_test_requirements()
> +{
> +    local config="/proc/config.gz"
> +    [[ -f "${config}" ]] || config="/boot/config-$(uname -r)"
> +    [[ -f "${config}" ]] || die "Cannot find kernel config in /proc or /boot"
> +
> +    # gzip -dcfq automatically handles both compressed and plaintext input.
> +    # See man 1 gzip under '-f'.
> +    local pg_table_levels=$(gzip -dcfq "${config}" | grep PGTABLE_LEVELS | cut -d'=' -f 2)
> +
> +    if [[ "${pg_table_levels}" -lt 5 ]]; then
> +        echo "$0: PG_TABLE_LEVELS=${pg_table_levels}, must be >= 5 to run this test"
> +        exit $ksft_skip
> +    fi
> +}

This prevent the test from running on powerpc architecture.

$bash -x  ./va_128TBswitch.sh  
+ exitcode=1
+ ksft_skip=4
+ check_test_requirements
+ local config=/proc/config.gz
+ [[ -f /proc/config.gz ]]
+ [[ -f /proc/config.gz ]]
++ gzip -dcfq /proc/config.gz
++ grep PGTABLE_LEVELS
++ cut -d= -f 2
+ local pg_table_levels=4
+ [[ 4 -lt 5 ]]
+ echo './va_128TBswitch.sh: PG_TABLE_LEVELS=4, must be >= 5 to run this test'
./va_128TBswitch.sh: PG_TABLE_LEVELS=4, must be >= 5 to run this test
+ exit 4

Without the patch

:src/linux/tools/testing/selftests/vm$ ./va_128TBswitch
mmap(ADDR_SWITCH_HINT - PAGE_SIZE, PAGE_SIZE): 0x7fffffff0000 - OK
mmap(ADDR_SWITCH_HINT - PAGE_SIZE, (2 * PAGE_SIZE)): 0x763910f30000 - OK
mmap(ADDR_SWITCH_HINT, PAGE_SIZE): 0x763910f40000 - OK
mmap(ADDR_SWITCH_HINT, 2 * PAGE_SIZE, MAP_FIXED): 0x800000000000 - OK
mmap(NULL): 0x763910f20000 - OK
mmap(LOW_ADDR): 0x40000000 - OK
mmap(HIGH_ADDR): 0x1000000000000 - OK
mmap(HIGH_ADDR) again: 0xff63910fc0000 - OK
mmap(HIGH_ADDR, MAP_FIXED): 0x1000000000000 - OK
mmap(-1): 0xff63910fa0000 - OK
mmap(-1) again: 0xff63910f80000 - OK
mmap(ADDR_SWITCH_HINT - PAGE_SIZE, PAGE_SIZE): 0x7fffffff0000 - OK
mmap(ADDR_SWITCH_HINT - PAGE_SIZE, 2 * PAGE_SIZE): 0x763910f20000 - OK
mmap(ADDR_SWITCH_HINT - PAGE_SIZE/2 , 2 * PAGE_SIZE): 0x763910f00000 - OK
mmap(ADDR_SWITCH_HINT, PAGE_SIZE): 0x763910ef0000 - OK
mmap(ADDR_SWITCH_HINT, 2 * PAGE_SIZE, MAP_FIXED): 0x800000000000 - OK
> +
> +check_test_requirements
> +./va_128TBswitch
> -- 
> 2.35.1