On Fri, Jan 30, 2026 at 10:59:14AM -0800, Nathan Chen via Devel wrote: > From: Nathan Chen <[email protected]> > > Implement the IOMMU_OPTION_RLIMIT_MODE > ioctl to set per-process memory accounting for > iommufd. This prevents ENOMEM errors from the > default per-user memory accounting when multiple > VMs under the libvirt-qemu user have their pinned > memory summed and checked against a per-process > RLIMIT_MEMLOCK limit. > > Signed-off-by: Nathan Chen <[email protected]> > --- > meson.build | 1 + > po/POTFILES | 1 + > src/libvirt_private.syms | 3 ++ > src/util/meson.build | 1 + > src/util/viriommufd.c | 111 +++++++++++++++++++++++++++++++++++++++ > src/util/viriommufd.h | 25 +++++++++ > 6 files changed, 142 insertions(+) > create mode 100644 src/util/viriommufd.c > create mode 100644 src/util/viriommufd.h
[...]
> diff --git a/src/util/viriommufd.c b/src/util/viriommufd.c
> new file mode 100644
> index 0000000000..b44bc8ed1d
> --- /dev/null
> +++ b/src/util/viriommufd.c
> @@ -0,0 +1,111 @@
> +#include <config.h>
> +
> +#include "viriommufd.h"
> +#include "virlog.h"
> +#include "virerror.h"
> +#include "virfile.h"
> +
> +#define VIR_FROM_THIS VIR_FROM_NONE
> +
> +VIR_LOG_INIT("util.iommufd");
> +
> +#ifdef __linux__
> +
> +# include <sys/ioctl.h>
> +# include <linux/types.h>
> +
> +# ifdef HAVE_LINUX_IOMMUFD_H
> +# include <linux/iommufd.h>
> +# endif
> +
> +# ifndef IOMMU_OPTION
> +
> +enum iommufd_option {
> + IOMMU_OPTION_RLIMIT_MODE = 0,
> + IOMMU_OPTION_HUGE_PAGES = 1,
> +};
> +
> +enum iommufd_option_ops {
> + IOMMU_OPTION_OP_SET = 0,
> + IOMMU_OPTION_OP_GET = 1,
> +};
> +
> +struct iommu_option {
> + __u32 size;
> + __u32 option_id;
> + __u16 op;
> + __u16 __reserved;
> + __u32 object_id;
> + __aligned_u64 val64;
> +};
> +
> +# define IOMMUFD_TYPE (';')
> +# define IOMMUFD_CMD_OPTION 0x87
> +# define IOMMU_OPTION _IO(IOMMUFD_TYPE, IOMMUFD_CMD_OPTION)
> +
> +# endif
> +
> +/**
> + * virIOMMUFDSetRLimitMode:
> + * @fd: iommufd file descriptor
> + * @processAccounting: true for per-process, false for per-user
> + *
> + * Set RLIMIT_MEMLOCK accounting mode for the iommufd.
> + *
> + * Returns: 0 on success, -1 on error
> + */
> +int
> +virIOMMUFDSetRLimitMode(int fd, bool processAccounting)
> +{
> + struct iommu_option option = {
> + .size = sizeof(struct iommu_option),
> + .option_id = IOMMU_OPTION_RLIMIT_MODE,
> + .op = IOMMU_OPTION_OP_SET,
> + .__reserved = 0,
> + .object_id = 0,
> + .val64 = processAccounting ? 1 : 0,
> + };
> +
> + if (ioctl(fd, IOMMU_OPTION, &option) < 0) {
> + switch (errno) {
> + case ENOTTY:
> + VIR_WARN("IOMMU_OPTION ioctl not supported");
> + return -1;
> +
> + case EOPNOTSUPP:
> + VIR_WARN("IOMMU_OPTION_RLIMIT_MODE not supported by kernel");
> + return -1;
> +
> + case EINVAL:
> + virReportSystemError(errno, "%s",
> + _("invalid iommufd option parameters"));
> + return -1;
> +
> + case EPERM:
> + VIR_WARN("Permission denied for IOMMU_OPTION ioctl. "
> + "Per-user-based memory accounting to be used by
> default.");
> + return -1;
> +
> + default:
> + virReportSystemError(errno, "%s",
> + _("failed to set iommufd option"));
> + return -1;
> + }
> + }
When we return -1 we should also set error instead of logging warning.
I can fix it before pushing, there are two options:
- We will keep the switch() and keep the customized messages and
call virReportSystemError() for each case
- Or we can remove the switch and call virReportSystemError that already
adds string representation of errno:
if (ioctl(fd, IOMMU_OPTION, &option) < 0) {
virReportSystemError(errno, "%s",
_("failed to set memory accounting for iommufd"));
return -1;
}
Pavel
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