| Message ID | 20240131014738.469858-4-jdamato@fastly.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Per epoll context busy poll support | expand |
On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote: > +struct epoll_params { > + __aligned_u64 busy_poll_usecs; > + __u16 busy_poll_budget; > + > + /* pad the struct to a multiple of 64bits for alignment on all arches */ > + __u8 __pad[6]; You HAVE to check this padding to be sure it is all 0, otherwise it can never be used in the future for anything. thanks, greg k-h
On Tue, Jan 30, 2024 at 06:08:36PM -0800, Greg Kroah-Hartman wrote: > On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote: > > +struct epoll_params { > > + __aligned_u64 busy_poll_usecs; > > + __u16 busy_poll_budget; > > + > > + /* pad the struct to a multiple of 64bits for alignment on all arches */ > > + __u8 __pad[6]; > > You HAVE to check this padding to be sure it is all 0, otherwise it can > never be used in the future for anything. Is there some preferred mechanism for this in the kernel that I should be using or is this as simple as adding a for loop to check each u8 == 0 ? Thanks.
On Tue, Jan 30, 2024 at 06:27:57PM -0800, Joe Damato wrote: > On Tue, Jan 30, 2024 at 06:08:36PM -0800, Greg Kroah-Hartman wrote: > > On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote: > > > +struct epoll_params { > > > + __aligned_u64 busy_poll_usecs; > > > + __u16 busy_poll_budget; > > > + > > > + /* pad the struct to a multiple of 64bits for alignment on all arches */ > > > + __u8 __pad[6]; > > > > You HAVE to check this padding to be sure it is all 0, otherwise it can > > never be used in the future for anything. > > Is there some preferred mechanism for this in the kernel that I should be > using or is this as simple as adding a for loop to check each u8 == 0 ? It's as simple as a loop :)
On Tue, Jan 30, 2024 at 06:27:57PM -0800, Joe Damato wrote: > On Tue, Jan 30, 2024 at 06:08:36PM -0800, Greg Kroah-Hartman wrote: > > On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote: > > > +struct epoll_params { > > > + __aligned_u64 busy_poll_usecs; > > > + __u16 busy_poll_budget; > > > + > > > + /* pad the struct to a multiple of 64bits for alignment on all arches */ > > > + __u8 __pad[6]; > > > > You HAVE to check this padding to be sure it is all 0, otherwise it can > > never be used in the future for anything. > > Is there some preferred mechanism for this in the kernel that I should be > using or is this as simple as adding a for loop to check each u8 == 0 ? memchr_inv() -Dave.
On 31. 01. 24, 3:27, Joe Damato wrote: > On Tue, Jan 30, 2024 at 06:08:36PM -0800, Greg Kroah-Hartman wrote: >> On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote: >>> +struct epoll_params { >>> + __aligned_u64 busy_poll_usecs; >>> + __u16 busy_poll_budget; >>> + >>> + /* pad the struct to a multiple of 64bits for alignment on all arches */ >>> + __u8 __pad[6]; >> >> You HAVE to check this padding to be sure it is all 0, otherwise it can >> never be used in the future for anything. > > Is there some preferred mechanism for this in the kernel that I should be > using or is this as simple as adding a for loop to check each u8 == 0 ? You are likely looking for memchr_inv().
On Wed, Jan 31, 2024 at 07:03:54AM +0100, Jiri Slaby wrote: > On 31. 01. 24, 3:27, Joe Damato wrote: > > On Tue, Jan 30, 2024 at 06:08:36PM -0800, Greg Kroah-Hartman wrote: > > > On Wed, Jan 31, 2024 at 01:47:33AM +0000, Joe Damato wrote: > > > > +struct epoll_params { > > > > + __aligned_u64 busy_poll_usecs; > > > > + __u16 busy_poll_budget; > > > > + > > > > + /* pad the struct to a multiple of 64bits for alignment on all arches */ > > > > + __u8 __pad[6]; > > > > > > You HAVE to check this padding to be sure it is all 0, otherwise it can > > > never be used in the future for anything. > > > > Is there some preferred mechanism for this in the kernel that I should be > > using or is this as simple as adding a for loop to check each u8 == 0 ? > > You are likely looking for memchr_inv(). Ah, never noticed that, thanks!
diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst index 457e16f06e04..b33918232f78 100644 --- a/Documentation/userspace-api/ioctl/ioctl-number.rst +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst @@ -309,6 +309,7 @@ Code Seq# Include File Comments 0x89 0B-DF linux/sockios.h 0x89 E0-EF linux/sockios.h SIOCPROTOPRIVATE range 0x89 F0-FF linux/sockios.h SIOCDEVPRIVATE range +0x8A 00-1F linux/eventpoll.h 0x8B all linux/wireless.h 0x8C 00-3F WiNRADiO driver <http://www.winradio.com.au/> diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 3985434df527..afdb91c6faa8 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -37,6 +37,7 @@ #include <linux/seq_file.h> #include <linux/compat.h> #include <linux/rculist.h> +#include <linux/capability.h> #include <net/busy_poll.h> /* @@ -495,6 +496,42 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) ep->napi_id = napi_id; } +static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct eventpoll *ep; + struct epoll_params epoll_params; + void __user *uarg = (void __user *) arg; + + ep = file->private_data; + + switch (cmd) { + case EPIOCSPARAMS: + if (copy_from_user(&epoll_params, uarg, sizeof(epoll_params))) + return -EFAULT; + + if (epoll_params.busy_poll_usecs > U32_MAX) + return -EINVAL; + + if (epoll_params.busy_poll_budget > NAPI_POLL_WEIGHT && + !capable(CAP_NET_ADMIN)) + return -EPERM; + + ep->busy_poll_usecs = epoll_params.busy_poll_usecs; + ep->busy_poll_budget = epoll_params.busy_poll_budget; + return 0; + case EPIOCGPARAMS: + memset(&epoll_params, 0, sizeof(epoll_params)); + epoll_params.busy_poll_usecs = ep->busy_poll_usecs; + epoll_params.busy_poll_budget = ep->busy_poll_budget; + if (copy_to_user(uarg, &epoll_params, sizeof(epoll_params))) + return -EFAULT; + return 0; + default: + return -ENOIOCTLCMD; + } +} + #else static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock) @@ -510,6 +547,12 @@ static inline bool ep_busy_loop_on(struct eventpoll *ep) { return false; } + +static long ep_eventpoll_bp_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + return -EOPNOTSUPP; +} #endif /* CONFIG_NET_RX_BUSY_POLL */ /* @@ -869,6 +912,26 @@ static void ep_clear_and_put(struct eventpoll *ep) ep_free(ep); } +static long ep_eventpoll_ioctl(struct file *file, unsigned int cmd, unsigned long arg) +{ + int ret; + + if (!is_file_epoll(file)) + return -EINVAL; + + switch (cmd) { + case EPIOCSPARAMS: + case EPIOCGPARAMS: + ret = ep_eventpoll_bp_ioctl(file, cmd, arg); + break; + default: + ret = -EINVAL; + break; + } + + return ret; +} + static int ep_eventpoll_release(struct inode *inode, struct file *file) { struct eventpoll *ep = file->private_data; @@ -975,6 +1038,8 @@ static const struct file_operations eventpoll_fops = { .release = ep_eventpoll_release, .poll = ep_eventpoll_poll, .llseek = noop_llseek, + .unlocked_ioctl = ep_eventpoll_ioctl, + .compat_ioctl = compat_ptr_ioctl, }; /* diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h index cfbcc4cc49ac..98e5ea525dd0 100644 --- a/include/uapi/linux/eventpoll.h +++ b/include/uapi/linux/eventpoll.h @@ -85,4 +85,16 @@ struct epoll_event { __u64 data; } EPOLL_PACKED; +struct epoll_params { + __aligned_u64 busy_poll_usecs; + __u16 busy_poll_budget; + + /* pad the struct to a multiple of 64bits for alignment on all arches */ + __u8 __pad[6]; +}; + +#define EPOLL_IOC_TYPE 0x8A +#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params) +#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params) + #endif /* _UAPI_LINUX_EVENTPOLL_H */
Add an ioctl for getting and setting epoll_params. User programs can use this ioctl to get and set the busy poll usec time or packet budget params for a specific epoll context. Parameters are limited: - busy_poll_usecs is limited to <= u32_max - busy_poll_budget is limited to <= NAPI_POLL_WEIGHT by unprivileged users (!capable(CAP_NET_ADMIN)). Signed-off-by: Joe Damato <jdamato@fastly.com> --- .../userspace-api/ioctl/ioctl-number.rst | 1 + fs/eventpoll.c | 65 +++++++++++++++++++ include/uapi/linux/eventpoll.h | 12 ++++ 3 files changed, 78 insertions(+)