Re: [PATCH v3 3/8] vfio: selftests: Introduce a sysfs lib

[Alex Williamson <alex@shazbot.org>]

On Wed,  4 Feb 2026 01:00:52 +0000
Raghavendra Rao Ananta <rananta@google.com> wrote:

> Introduce a sysfs library to handle the common reads/writes to the
> PCI sysfs files, for example, getting the total number of VFs supported
> by the device via /sys/bus/pci/devices/$BDF/sriov_totalvfs. The library
> will be used in the upcoming test patch to configure the VFs for a given
> PF device.
> 
> Opportunistically, move vfio_pci_get_group_from_dev() to this library as
> it falls under the same bucket. Rename it to sysfs_iommu_group_get() to
> align with other function names.
> 
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> ---
>  .../selftests/vfio/lib/include/libvfio.h      |   1 +
>  .../vfio/lib/include/libvfio/sysfs.h          |  12 ++
>  tools/testing/selftests/vfio/lib/libvfio.mk   |   1 +
>  tools/testing/selftests/vfio/lib/sysfs.c      | 136 ++++++++++++++++++
>  .../selftests/vfio/lib/vfio_pci_device.c      |  22 +--
>  5 files changed, 151 insertions(+), 21 deletions(-)
>  create mode 100644 tools/testing/selftests/vfio/lib/include/libvfio/sysfs.h
>  create mode 100644 tools/testing/selftests/vfio/lib/sysfs.c
> 
> diff --git a/tools/testing/selftests/vfio/lib/include/libvfio.h b/tools/testing/selftests/vfio/lib/include/libvfio.h
> index 279ddcd70194..bbe1d7616a64 100644
> --- a/tools/testing/selftests/vfio/lib/include/libvfio.h
> +++ b/tools/testing/selftests/vfio/lib/include/libvfio.h
> @@ -5,6 +5,7 @@
>  #include <libvfio/assert.h>
>  #include <libvfio/iommu.h>
>  #include <libvfio/iova_allocator.h>
> +#include <libvfio/sysfs.h>
>  #include <libvfio/vfio_pci_device.h>
>  #include <libvfio/vfio_pci_driver.h>
>  
> diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/sysfs.h b/tools/testing/selftests/vfio/lib/include/libvfio/sysfs.h
> new file mode 100644
> index 000000000000..c48d5ef00ba6
> --- /dev/null
> +++ b/tools/testing/selftests/vfio/lib/include/libvfio/sysfs.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef SELFTESTS_VFIO_LIB_INCLUDE_LIBVFIO_SYSFS_H
> +#define SELFTESTS_VFIO_LIB_INCLUDE_LIBVFIO_SYSFS_H
> +
> +int sysfs_sriov_totalvfs_get(const char *bdf);
> +int sysfs_sriov_numvfs_get(const char *bdf);
> +void sysfs_sriov_numvfs_set(const char *bdfs, int numvfs);
> +char *sysfs_sriov_vf_bdf_get(const char *pf_bdf, int i);
> +unsigned int sysfs_iommu_group_get(const char *bdf);
> +char *sysfs_driver_get(const char *bdf);
> +
> +#endif /* SELFTESTS_VFIO_LIB_INCLUDE_LIBVFIO_SYSFS_H */
> diff --git a/tools/testing/selftests/vfio/lib/libvfio.mk b/tools/testing/selftests/vfio/lib/libvfio.mk
> index 9f47bceed16f..b7857319c3f1 100644
> --- a/tools/testing/selftests/vfio/lib/libvfio.mk
> +++ b/tools/testing/selftests/vfio/lib/libvfio.mk
> @@ -6,6 +6,7 @@ LIBVFIO_SRCDIR := $(selfdir)/vfio/lib
>  LIBVFIO_C := iommu.c
>  LIBVFIO_C += iova_allocator.c
>  LIBVFIO_C += libvfio.c
> +LIBVFIO_C += sysfs.c
>  LIBVFIO_C += vfio_pci_device.c
>  LIBVFIO_C += vfio_pci_driver.c
>  
> diff --git a/tools/testing/selftests/vfio/lib/sysfs.c b/tools/testing/selftests/vfio/lib/sysfs.c
> new file mode 100644
> index 000000000000..f01598ff15d7
> --- /dev/null
> +++ b/tools/testing/selftests/vfio/lib/sysfs.c
> @@ -0,0 +1,136 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <linux/limits.h>
> +
> +#include <libvfio.h>
> +
> +static int sysfs_val_get(const char *component, const char *name,
> +			 const char *file)
> +{
> +	char path[PATH_MAX];
> +	char buf[32];
> +	int fd;
> +
> +	snprintf_assert(path, PATH_MAX, "/sys/bus/pci/%s/%s/%s", component, name, file);
> +	fd = open(path, O_RDONLY);
> +	if (fd < 0)
> +		return fd;
> +
> +	VFIO_ASSERT_GT(read(fd, buf, ARRAY_SIZE(buf)), 0);
> +	VFIO_ASSERT_EQ(close(fd), 0);
> +
> +	return strtol(buf, NULL, 0);

I'm surprised we're not sanitizing the strtol() here, ie.

	errno = 0;
	ret = strtol(buf, NULL, 0);
	VFIO_ASSERT_EQ(errno, 0, "sysfs path \"%s\" is not an integer: \"%s\"\n", path, buf);

	return ret;

We also need that sign-off on 7/8.  Thanks,

Alex