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Date:   Mon, 28 Sep 2020 10:02:45 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Jonathan Corbet <corbet@lwn.net>,
        =?utf-8?B?SsOpcsO0bWU=?= Glisse <jglisse@redhat.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Shuah Khan <shuah@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
        linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-s390@vger.kernel.org
Subject: Re: [PATCH 8/8] selftests/vm: hmm-tests: remove the libhugetlbfs
 dependency
Message-ID: <20200928130245.GQ9916@ziepe.ca>
References: <20200928062159.923212-1-jhubbard@nvidia.com>
 <20200928062159.923212-9-jhubbard@nvidia.com>
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In-Reply-To: <20200928062159.923212-9-jhubbard@nvidia.com>
Precedence: bulk

On Sun, Sep 27, 2020 at 11:21:59PM -0700, John Hubbard wrote:

> @@ -76,8 +79,6 @@ TEST_FILES := test_vmalloc.sh
>  KSFT_KHDR_INSTALL := 1
>  include ../lib.mk
>  
> -$(OUTPUT)/hmm-tests: LDLIBS += -lhugetlbfs
> -
>  ifeq ($(ARCH),x86_64)
>  BINARIES_32 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_32))
>  BINARIES_64 := $(patsubst %,$(OUTPUT)/%,$(BINARIES_64))
> @@ -130,3 +131,22 @@ endif
>  $(OUTPUT)/mlock-random-test: LDLIBS += -lcap
>  
>  $(OUTPUT)/gup_test: ../../../../mm/gup_test.h
> +
> +$(OUTPUT)/hmm-tests: local_config.h
> +
> +# HMM_EXTRA_LIBS may get set in local_config.mk, or it may be left empty.
> +$(OUTPUT)/hmm-tests: LDLIBS += $(HMM_EXTRA_LIBS)
> +
> +local_config.mk local_config.h: check_config.sh
> +	./check_config.sh
> +
> +EXTRA_CLEAN += local_config.mk local_config.h
> +
> +ifeq ($(HMM_EXTRA_LIBS),)
> +all: warn_missing_hugelibs
> +
> +warn_missing_hugelibs:
> +	@echo ; \
> +	echo "Warning: missing libhugetlbfs support. Some HMM tests will be skipped." ; \
> +	echo
> +endif
> diff --git a/tools/testing/selftests/vm/check_config.sh b/tools/testing/selftests/vm/check_config.sh
> new file mode 100755
> index 000000000000..651a4b192479
> +++ b/tools/testing/selftests/vm/check_config.sh
> @@ -0,0 +1,30 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Probe for libraries and create header files to record the results. Both C
> +# header files and Makefile include fragments are created.
> +
> +OUTPUT_H_FILE=local_config.h
> +OUTPUT_MKFILE=local_config.mk
> +
> +# libhugetlbfs
> +tmpname=$(mktemp)
> +tmpfile_c=${tmpname}.c
> +tmpfile_o=${tmpname}.o
> +
> +echo "#include <sys/types.h>"        > $tmpfile_c
> +echo "#include <hugetlbfs.h>"       >> $tmpfile_c
> +echo "int func(void) { return 0; }" >> $tmpfile_c
> +
> +gcc -c $tmpfile_c -o $tmpfile_o >/dev/null 2>&1

This gcc has to come from some makefile variable

This is kind of janky :\

Could we just not use libhugetlbfs? Doesn't it all just boil down to
creating a file in /dev/huge? Eg look at tools/testing/selftests/vm/hugepage-mmap.c

Jason