linux-ext4 - Re: [PATCH 3/3] tools: add hmm gup test for long term pinned device pages

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Date:   Tue, 1 Feb 2022 10:09:13 -0500
From:   Felix Kuehling <felix.kuehling@....com>
To:     Alistair Popple <apopple@...dia.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org
Cc:     rcampbell@...dia.com, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, hch@....de, jgg@...dia.com,
        jglisse@...hat.com, willy@...radead.org, alex.sierra@....com,
        jhubbard@...dia.com
Subject: Re: [PATCH 3/3] tools: add hmm gup test for long term pinned device
 pages


Am 2022-02-01 um 02:05 schrieb Alistair Popple:
> From: Alex Sierra <alex.sierra@....com>
>
> The intention is to test device coherent type pages that have been
> called through get user pages with PIN_LONGTERM flag set. These pages
> should get migrated back to normal system memory.
>
> Signed-off-by: Alex Sierra <alex.sierra@....com>
> Signed-off-by: Alistair Popple <apopple@...dia.com>

This patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling@....com>


> ---
>   tools/testing/selftests/vm/Makefile    |  2 +-
>   tools/testing/selftests/vm/hmm-tests.c | 81 +++++++++++++++++++++++++++-
>   2 files changed, 82 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
> index 1607322..58c8427 100644
> --- a/tools/testing/selftests/vm/Makefile
> +++ b/tools/testing/selftests/vm/Makefile
> @@ -142,7 +142,7 @@ $(OUTPUT)/mlock-random-test $(OUTPUT)/memfd_secret: LDLIBS += -lcap
>   
>   $(OUTPUT)/gup_test: ../../../../mm/gup_test.h
>   
> -$(OUTPUT)/hmm-tests: local_config.h
> +$(OUTPUT)/hmm-tests: local_config.h ../../../../mm/gup_test.h
>   
>   # HMM_EXTRA_LIBS may get set in local_config.mk, or it may be left empty.
>   $(OUTPUT)/hmm-tests: LDLIBS += $(HMM_EXTRA_LIBS)
> diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
> index 84ec8c4..11b83a8 100644
> --- a/tools/testing/selftests/vm/hmm-tests.c
> +++ b/tools/testing/selftests/vm/hmm-tests.c
> @@ -36,6 +36,7 @@
>    * in the usual include/uapi/... directory.
>    */
>   #include "../../../../lib/test_hmm_uapi.h"
> +#include "../../../../mm/gup_test.h"
>   
>   struct hmm_buffer {
>   	void		*ptr;
> @@ -60,6 +61,8 @@ enum {
>   #define NTIMES		10
>   
>   #define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1)))
> +/* Just the flags we need, copied from mm.h: */
> +#define FOLL_WRITE	0x01	/* check pte is writable */
>   
>   FIXTURE(hmm)
>   {
> @@ -1766,4 +1769,82 @@ TEST_F(hmm, exclusive_cow)
>   	hmm_buffer_free(buffer);
>   }
>   
> +/*
> + * Test get user device pages through gup_test. Setting PIN_LONGTERM flag.
> + * This should trigger a migration back to system memory for both, private
> + * and coherent type pages.
> + * This test makes use of gup_test module. Make sure GUP_TEST_CONFIG is added
> + * to your configuration before you run it.
> + */
> +TEST_F(hmm, hmm_gup_test)
> +{
> +	struct hmm_buffer *buffer;
> +	struct gup_test gup;
> +	int gup_fd;
> +	unsigned long npages;
> +	unsigned long size;
> +	unsigned long i;
> +	int *ptr;
> +	int ret;
> +	unsigned char *m;
> +
> +	gup_fd = open("/sys/kernel/debug/gup_test", O_RDWR);
> +	if (gup_fd == -1)
> +		SKIP(return, "Skipping test, could not find gup_test driver");
> +
> +	npages = 4;
> +	ASSERT_NE(npages, 0);
> +	size = npages << self->page_shift;
> +
> +	buffer = malloc(sizeof(*buffer));
> +	ASSERT_NE(buffer, NULL);
> +
> +	buffer->fd = -1;
> +	buffer->size = size;
> +	buffer->mirror = malloc(size);
> +	ASSERT_NE(buffer->mirror, NULL);
> +
> +	buffer->ptr = mmap(NULL, size,
> +			   PROT_READ | PROT_WRITE,
> +			   MAP_PRIVATE | MAP_ANONYMOUS,
> +			   buffer->fd, 0);
> +	ASSERT_NE(buffer->ptr, MAP_FAILED);
> +
> +	/* Initialize buffer in system memory. */
> +	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
> +		ptr[i] = i;
> +
> +	/* Migrate memory to device. */
> +	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
> +	ASSERT_EQ(ret, 0);
> +	ASSERT_EQ(buffer->cpages, npages);
> +	/* Check what the device read. */
> +	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
> +		ASSERT_EQ(ptr[i], i);
> +
> +	gup.nr_pages_per_call = npages;
> +	gup.addr = (unsigned long)buffer->ptr;
> +	gup.gup_flags = FOLL_WRITE;
> +	gup.size = size;
> +	/*
> +	 * Calling gup_test ioctl. It will try to PIN_LONGTERM these device pages
> +	 * causing a migration back to system memory for both, private and coherent
> +	 * type pages.
> +	 */
> +	if (ioctl(gup_fd, PIN_LONGTERM_BENCHMARK, &gup)) {
> +		perror("ioctl on PIN_LONGTERM_BENCHMARK\n");
> +		goto out_test;
> +	}
> +
> +	/* Take snapshot to make sure pages have been migrated to sys memory */
> +	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages);
> +	ASSERT_EQ(ret, 0);
> +	ASSERT_EQ(buffer->cpages, npages);
> +	m = buffer->mirror;
> +	for (i = 0; i < npages; i++)
> +		ASSERT_EQ(m[i], HMM_DMIRROR_PROT_WRITE);
> +out_test:
> +	close(gup_fd);
> +	hmm_buffer_free(buffer);
> +}
>   TEST_HARNESS_MAIN