Re: [PATCH v2] selftests/vm: Only run 128TBswitch with 5-level paging

[David Vernet <void@manifault.com>]

On Mon, Jun 27, 2022 at 06:13:32PM +0200, Adam Sindelar wrote:
> 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 `sudo make -C tools/testing/selftests TARGETS=vm run_tests`
> produces the desired output:
> 
> ```
> ---------------------------
> running ./va_128TBswitch.sh
> ---------------------------
> ./va_128TBswitch.sh: PG_TABLE_LEVELS=4, must be >= 5 to run this test
> [SKIP]
> -------------------------------
> ```

Different subsystems have different workflows, but I don't recall having
ever seen markdown used in any mm patches. Can you update the patch
description to not use markdown?

> v2:
>   - Function variables declared local
>   - Fixed variable name typo in Makefile
>   - Comment to explain gzip -dcfq

Can you move the version-change descriptions out of the commit summary and
into the patch itself, directly after the ---? We don't want it to be
included in the changelog that eventually gets merged. This is described in
more detail in [0].

[0] https://www.kernel.org/doc/html/latest/process/submitting-patches.html#the-canonical-patch-format

> Signed-off-by: Adam Sindelar <adam@wowsignal.io>
> ---
>  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

Agreed that it's preferable to follow the contours that already exist in
the vm/ tests, but IMO this is pretty confusing and should be fixed for the
whole suite in a follow-on patch. Both ksft_skip and exitcode are exit
codes so this variable name doesn't really make sense.

> +# Kselftest framework requirement - SKIP code is 4.
> +ksft_skip=4
> +
> +die()

Sorry, missed this on the first pass, but can we change the name of this
function to fail() to show that we're failing the test rather than killing
the testrun?

> +{
> +    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
> +}
> +
> +check_test_requirements
> +./va_128TBswitch
> -- 
> 2.35.1