Stratos-dev August 2023

stratos-dev@op-lists.linaro.org

3 participants
5 discussions

[PATCH 0/2] xen: privcmd: Add ioeventfd support

by Viresh Kumar

Hello, Now that irqfd support (backend to guest interrupt) is already merged, this series solves the other part of the problem, i.e. ioeventfd (guest to backend interrupt). More details inside the commits. -- Viresh Viresh Kumar (2): xen: evtchn: Allow shared registration of IRQ handers xen: privcmd: Add support for ioeventfd drivers/xen/Kconfig | 8 +- drivers/xen/events/events_base.c | 1 + drivers/xen/evtchn.c | 2 +- drivers/xen/privcmd.c | 385 +++++++++++++++++++++++++++++- include/uapi/xen/privcmd.h | 18 ++ include/xen/interface/hvm/ioreq.h | 51 ++++ 6 files changed, 458 insertions(+), 7 deletions(-) create mode 100644 include/xen/interface/hvm/ioreq.h -- 2.31.1.272.g89b43f80a514

6 months, 3 weeks

[PATCH] xen-ioctl: Add support to set-ioeventfd via privcmd

by Viresh Kumar

This adds support to issue the set ioeventfd ioctl via the privcmd file. Signed-off-by: Viresh Kumar <viresh.kumar(a)linaro.org> --- Mathieu, Please don't apply it unless the kernel counterpart is merged. crates/xen-ioctls/Cargo.toml | 1 + crates/xen-ioctls/src/private.rs | 16 +++++- crates/xen-ioctls/src/xdm/types.rs | 18 +++++++ crates/xen-ioctls/src/xdm/xdm.rs | 82 ++++++++++++++++++++++++++++++ 4 files changed, 116 insertions(+), 1 deletion(-) diff --git a/crates/xen-ioctls/Cargo.toml b/crates/xen-ioctls/Cargo.toml index a9e26f9fe0e0..bc4d21e5847b 100644 --- a/crates/xen-ioctls/Cargo.toml +++ b/crates/xen-ioctls/Cargo.toml @@ -11,3 +11,4 @@ edition = "2018" [dependencies] libc = ">=0.2.95" vmm-sys-util = ">=0.9.0" +xen-bindings = { path = "../xen-bindings" } diff --git a/crates/xen-ioctls/src/private.rs b/crates/xen-ioctls/src/private.rs index 59a75f67f18d..23456e383377 100644 --- a/crates/xen-ioctls/src/private.rs +++ b/crates/xen-ioctls/src/private.rs @@ -14,7 +14,9 @@ use std::io::Error; use std::os::unix::io::AsRawFd; use vmm_sys_util::ioctl::_IOC_NONE; -use crate::xdm::types::{PrivcmdDeviceModelIrqFd, PrivcmdDeviceModelOp}; +use crate::xdm::types::{ + PrivcmdDeviceModelIoeventFd, PrivcmdDeviceModelIrqFd, PrivcmdDeviceModelOp, +}; use crate::xfm::types::{PrivCmdMmapBatchV2, PrivCmdMmapResource}; pub const PAGE_SHIFT: u32 = 12; @@ -85,6 +87,18 @@ ioctl_ioc_nr!( std::mem::size_of::<PrivcmdDeviceModelIrqFd>() as u32 ); +/* + * #define IOCTL_PRIVCMD_IOEVENTFD \ + * _IOC(_IOC_NONE, 'P', 9, sizeof(privcmd_ioeventfd_t)) + */ +ioctl_ioc_nr!( + IOCTL_PRIVCMD_IOEVENTFD, + _IOC_NONE, + XEN_PRIVCMD_TYPE, + 9 as u32, + std::mem::size_of::<PrivcmdDeviceModelIoeventFd>() as u32 +); + pub const HYPERCALL_EVTCHN: &str = "/dev/xen/evtchn"; pub const HYPERCALL_PRIVCMD: &str = "/dev/xen/privcmd"; pub const HYPERCALL_BUFFER_FILE: &str = "/dev/xen/hypercall"; diff --git a/crates/xen-ioctls/src/xdm/types.rs b/crates/xen-ioctls/src/xdm/types.rs index b000a68f0cf1..963583e34b97 100644 --- a/crates/xen-ioctls/src/xdm/types.rs +++ b/crates/xen-ioctls/src/xdm/types.rs @@ -157,3 +157,21 @@ pub struct PrivcmdDeviceModelIrqFd { pub domid: u16, pub pad: [u8; 2], } + +pub const PRIVCMD_IOEVENTFD_FLAG_DEASSIGN: u32 = 1; + +#[repr(C)] +#[derive(Debug, Copy, Clone)] +// tools/include/xen-sys/Linux/privcmd.h::privcmd_ioeventfd +pub struct PrivcmdDeviceModelIoeventFd { + pub ioreq: *mut c_void, + pub ports: *const u32, + pub addr: u64, + pub addr_len: u32, + pub event_fd: u32, + pub vcpus: u32, + pub vq: u32, + pub flags: u32, + pub domid: u16, + pub pad: [u8; 2], +} diff --git a/crates/xen-ioctls/src/xdm/xdm.rs b/crates/xen-ioctls/src/xdm/xdm.rs index 3aa5289794fe..5a30d109e65f 100644 --- a/crates/xen-ioctls/src/xdm/xdm.rs +++ b/crates/xen-ioctls/src/xdm/xdm.rs @@ -17,6 +17,8 @@ use std::os::unix::io::AsRawFd; use vmm_sys_util::eventfd::EventFd; +use xen_bindings::bindings::ioreq; + #[cfg(target_arch = "aarch64")] use crate::aarch64::types::*; #[cfg(target_arch = "x86_64")] @@ -307,4 +309,84 @@ impl XenDeviceModelHandle { ) -> Result<(), std::io::Error> { self.config_irqfd(fd, domid, irq, level, PRIVCMD_IRQFD_FLAG_DEASSIGN) } + + pub fn config_ioeventfd( + &self, + kick: &EventFd, + ioreq: &mut ioreq, + ports: &[u32], + addr: u64, + addr_len: u32, + vq: u32, + vcpus: u32, + domid: u16, + flags: u32, + ) -> Result<(), std::io::Error> { + let mut ioeventfd = PrivcmdDeviceModelIoeventFd { + ioreq: ioreq as *mut _ as *mut c_void, + ports: ports as *const _ as *const u32, + addr, + addr_len, + event_fd: kick.as_raw_fd() as u32, + vcpus, + vq, + flags, + domid, + pad: [0; 2], + }; + + let ret = unsafe { + // The expression "&mut ioeventfd as *mut _" creates a reference to ioeventfd before casting it + // to a *mut c_void. + ioctl( + self.fd.as_raw_fd(), + IOCTL_PRIVCMD_IOEVENTFD(), + &mut ioeventfd as *mut _ as *mut c_void, + ) + }; + + if ret < 0 { + return Err(Error::last_os_error()); + } + + Ok(()) + } + + pub fn set_ioeventfd( + &self, + kick: &EventFd, + ioreq: &mut ioreq, + ports: &[u32], + addr: u64, + addr_len: u32, + vq: u32, + vcpus: u32, + domid: u16, + ) -> Result<(), std::io::Error> { + self.config_ioeventfd(kick, ioreq, ports, addr, addr_len, vq, vcpus, domid, 0) + } + + pub fn clear_ioeventfd( + &self, + kick: &EventFd, + ioreq: &mut ioreq, + ports: &[u32], + addr: u64, + addr_len: u32, + vq: u32, + vcpus: u32, + domid: u16, + ) -> Result<(), std::io::Error> { + self.config_ioeventfd( + kick, + ioreq, + ports, + addr, + addr_len, + vq, + vcpus, + domid, + PRIVCMD_IOEVENTFD_FLAG_DEASSIGN, + ) + } } -- 2.31.1.272.g89b43f80a514

8 months

[PATCH V3] xen-ioctl: Add support to set-irqfd via privcmd

by Viresh Kumar

This adds support to issue the set irqfd ioctl via the privcmd file. Signed-off-by: Viresh Kumar <viresh.kumar(a)linaro.org> --- V3: - Based on changes merged in kernel. V2: - Fixed comment crates/xen-ioctls/src/private.rs | 14 +++++- crates/xen-ioctls/src/xdm/types.rs | 14 ++++++ crates/xen-ioctls/src/xdm/xdm.rs | 68 ++++++++++++++++++++++++++++++ 3 files changed, 95 insertions(+), 1 deletion(-) diff --git a/crates/xen-ioctls/src/private.rs b/crates/xen-ioctls/src/private.rs index 2d3379213e03..59a75f67f18d 100644 --- a/crates/xen-ioctls/src/private.rs +++ b/crates/xen-ioctls/src/private.rs @@ -14,8 +14,8 @@ use std::io::Error; use std::os::unix::io::AsRawFd; use vmm_sys_util::ioctl::_IOC_NONE; +use crate::xdm::types::{PrivcmdDeviceModelIrqFd, PrivcmdDeviceModelOp}; use crate::xfm::types::{PrivCmdMmapBatchV2, PrivCmdMmapResource}; -use crate::xdm::types::PrivcmdDeviceModelOp; pub const PAGE_SHIFT: u32 = 12; pub const PAGE_SIZE: u32 = 1 << PAGE_SHIFT; @@ -73,6 +73,18 @@ ioctl_ioc_nr!( std::mem::size_of::<PrivCmdMmapResource>() as u32 ); +/* + * #define IOCTL_PRIVCMD_IRQFD \ + * _IOC(_IOC_NONE, 'P', 8, sizeof(privcmd_irqfd_t)) + */ +ioctl_ioc_nr!( + IOCTL_PRIVCMD_IRQFD, + _IOC_NONE, + XEN_PRIVCMD_TYPE, + 8 as u32, + std::mem::size_of::<PrivcmdDeviceModelIrqFd>() as u32 +); + pub const HYPERCALL_EVTCHN: &str = "/dev/xen/evtchn"; pub const HYPERCALL_PRIVCMD: &str = "/dev/xen/privcmd"; pub const HYPERCALL_BUFFER_FILE: &str = "/dev/xen/hypercall"; diff --git a/crates/xen-ioctls/src/xdm/types.rs b/crates/xen-ioctls/src/xdm/types.rs index ea429558b852..b000a68f0cf1 100644 --- a/crates/xen-ioctls/src/xdm/types.rs +++ b/crates/xen-ioctls/src/xdm/types.rs @@ -143,3 +143,17 @@ impl PrivcmdDeviceModelOp { PrivcmdDeviceModelOp { domid, num, ubufs } } } + +pub const PRIVCMD_IRQFD_FLAG_DEASSIGN: u32 = 1; + +#[repr(C)] +#[derive(Debug, Copy, Clone)] +// tools/include/xen-sys/Linux/privcmd.h::privcmd_irqfd +pub struct PrivcmdDeviceModelIrqFd { + pub dm_op: *mut c_void, + pub size: u32, + pub fd: u32, + pub flags: u32, + pub domid: u16, + pub pad: [u8; 2], +} diff --git a/crates/xen-ioctls/src/xdm/xdm.rs b/crates/xen-ioctls/src/xdm/xdm.rs index 115724284b7e..3aa5289794fe 100644 --- a/crates/xen-ioctls/src/xdm/xdm.rs +++ b/crates/xen-ioctls/src/xdm/xdm.rs @@ -15,6 +15,8 @@ use std::fs::{File, OpenOptions}; use std::io::Error; use std::os::unix::io::AsRawFd; +use vmm_sys_util::eventfd::EventFd; + #[cfg(target_arch = "aarch64")] use crate::aarch64::types::*; #[cfg(target_arch = "x86_64")] @@ -239,4 +241,70 @@ impl XenDeviceModelHandle { do_dm_op(&self.fd, domid, &mut privcmd_dm_op_buffers) } + + pub fn config_irqfd( + &self, + fd: EventFd, + domid: u16, + irq: u32, + level: u8, + flags: u32, + ) -> Result<(), std::io::Error> { + let mut dm_op = XenDeviceModelOp { + op: XEN_DMOP_set_irq_level, + pad: 0, + u: XenDeviceModelOpPayload { + xen_set_irq_level: XenDeviceModelSetIrqLevel { + irq, + level, + ..Default::default() + }, + }, + }; + + let mut irqfd = PrivcmdDeviceModelIrqFd { + dm_op: &mut dm_op as *mut _ as *mut c_void, + size: std::mem::size_of::<XenDeviceModelOp>() as u32, + fd: fd.as_raw_fd() as u32, + flags, + domid, + pad: [0; 2], + }; + + let ret = unsafe { + // The expression "&mut irqfd as *mut _" creates a reference to irqfd before casting it + // to a *mut c_void. + ioctl( + self.fd.as_raw_fd(), + IOCTL_PRIVCMD_IRQFD(), + &mut irqfd as *mut _ as *mut c_void, + ) + }; + + if ret < 0 { + return Err(Error::last_os_error()); + } + + Ok(()) + } + + pub fn set_irqfd( + &self, + fd: EventFd, + domid: u16, + irq: u32, + level: u8, + ) -> Result<(), std::io::Error> { + self.config_irqfd(fd, domid, irq, level, 0) + } + + pub fn clear_irqfd( + &self, + fd: EventFd, + domid: u16, + irq: u32, + level: u8, + ) -> Result<(), std::io::Error> { + self.config_irqfd(fd, domid, irq, level, PRIVCMD_IRQFD_FLAG_DEASSIGN) + } } -- 2.31.1.272.g89b43f80a514

8 months, 1 week

[PATCH V5] xen: privcmd: Add support for irqfd

by Viresh Kumar

Xen provides support for injecting interrupts to the guests via the HYPERVISOR_dm_op() hypercall. The same is used by the Virtio based device backend implementations, in an inefficient manner currently. Generally, the Virtio backends are implemented to work with the Eventfd based mechanism. In order to make such backends work with Xen, another software layer needs to poll the Eventfds and raise an interrupt to the guest using the Xen based mechanism. This results in an extra context switch. This is not a new problem in Linux though. It is present with other hypervisors like KVM, etc. as well. The generic solution implemented in the kernel for them is to provide an IOCTL call to pass the interrupt details and eventfd, which lets the kernel take care of polling the eventfd and raising of the interrupt, instead of handling this in user space (which involves an extra context switch). This patch adds support to inject a specific interrupt to guest using the eventfd mechanism, by preventing the extra context switch. Inspired by existing implementations for KVM, etc.. Signed-off-by: Viresh Kumar <viresh.kumar(a)linaro.org> --- V4->V5 - Drop "default m" and update description in Kconfig. - Drop INIT_LIST_HEAD() for kirqfd->list. - Drop local "eventfd" variable. - Drop unnecessary !! usage. V3->V4 - Drop the imported definitions to hvm/dm_op.h. - Make the caller pass a pointer to pre-filled "struct xen_dm_op" instance and get rid of irq and level fields. - Enable the irqfd feature under a new Kconfig entry. V2->V3 - Select EVENTFD from Kconfig V1->V2: - Improve error handling. - Remove the unnecessary usage of list_for_each_entry_safe(). - Restrict the use of XEN_DMOP_set_irq_level to only ARM64. - Import definitions from Xen to hvm/dm_op.h. drivers/xen/Kconfig | 7 + drivers/xen/privcmd.c | 282 ++++++++++++++++++++++++++++++++++++- include/uapi/xen/privcmd.h | 14 ++ 3 files changed, 301 insertions(+), 2 deletions(-) diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index d5d7c402b651..d43153fec18e 100644 --- a/drivers/xen/Kconfig +++ b/drivers/xen/Kconfig @@ -269,6 +269,13 @@ config XEN_PRIVCMD disaggregated Xen setups this driver might be needed for other domains, too. +config XEN_PRIVCMD_IRQFD + bool "Xen irqfd support" + depends on XEN_PRIVCMD && XEN_VIRTIO && EVENTFD + help + Using the irqfd mechanism a virtio backend running in a daemon can + speed up interrupt injection into a guest. + config XEN_ACPI_PROCESSOR tristate "Xen ACPI processor" depends on XEN && XEN_PV_DOM0 && X86 && ACPI_PROCESSOR && CPU_FREQ diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index e2f580e30a86..120af57999fc 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -9,11 +9,16 @@ #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt +#include <linux/eventfd.h> +#include <linux/file.h> #include <linux/kernel.h> #include <linux/module.h> +#include <linux/mutex.h> +#include <linux/poll.h> #include <linux/sched.h> #include <linux/slab.h> #include <linux/string.h> +#include <linux/workqueue.h> #include <linux/errno.h> #include <linux/mm.h> #include <linux/mman.h> @@ -833,6 +838,263 @@ static long privcmd_ioctl_mmap_resource(struct file *file, return rc; } +#ifdef CONFIG_XEN_PRIVCMD_IRQFD +/* Irqfd support */ +static struct workqueue_struct *irqfd_cleanup_wq; +static DEFINE_MUTEX(irqfds_lock); +static LIST_HEAD(irqfds_list); + +struct privcmd_kernel_irqfd { + struct xen_dm_op_buf xbufs; + domid_t dom; + bool error; + struct eventfd_ctx *eventfd; + struct work_struct shutdown; + wait_queue_entry_t wait; + struct list_head list; + poll_table pt; +}; + +static void irqfd_deactivate(struct privcmd_kernel_irqfd *kirqfd) +{ + lockdep_assert_held(&irqfds_lock); + + list_del_init(&kirqfd->list); + queue_work(irqfd_cleanup_wq, &kirqfd->shutdown); +} + +static void irqfd_shutdown(struct work_struct *work) +{ + struct privcmd_kernel_irqfd *kirqfd = + container_of(work, struct privcmd_kernel_irqfd, shutdown); + u64 cnt; + + eventfd_ctx_remove_wait_queue(kirqfd->eventfd, &kirqfd->wait, &cnt); + eventfd_ctx_put(kirqfd->eventfd); + kfree(kirqfd); +} + +static void irqfd_inject(struct privcmd_kernel_irqfd *kirqfd) +{ + u64 cnt; + long rc; + + eventfd_ctx_do_read(kirqfd->eventfd, &cnt); + + xen_preemptible_hcall_begin(); + rc = HYPERVISOR_dm_op(kirqfd->dom, 1, &kirqfd->xbufs); + xen_preemptible_hcall_end(); + + /* Don't repeat the error message for consecutive failures */ + if (rc && !kirqfd->error) { + pr_err("Failed to configure irq for guest domain: %d\n", + kirqfd->dom); + } + + kirqfd->error = rc; +} + +static int +irqfd_wakeup(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key) +{ + struct privcmd_kernel_irqfd *kirqfd = + container_of(wait, struct privcmd_kernel_irqfd, wait); + __poll_t flags = key_to_poll(key); + + if (flags & EPOLLIN) + irqfd_inject(kirqfd); + + if (flags & EPOLLHUP) { + mutex_lock(&irqfds_lock); + irqfd_deactivate(kirqfd); + mutex_unlock(&irqfds_lock); + } + + return 0; +} + +static void +irqfd_poll_func(struct file *file, wait_queue_head_t *wqh, poll_table *pt) +{ + struct privcmd_kernel_irqfd *kirqfd = + container_of(pt, struct privcmd_kernel_irqfd, pt); + + add_wait_queue_priority(wqh, &kirqfd->wait); +} + +static int privcmd_irqfd_assign(struct privcmd_irqfd *irqfd) +{ + struct privcmd_kernel_irqfd *kirqfd, *tmp; + __poll_t events; + struct fd f; + void *dm_op; + int ret; + + kirqfd = kzalloc(sizeof(*kirqfd) + irqfd->size, GFP_KERNEL); + if (!kirqfd) + return -ENOMEM; + dm_op = kirqfd + 1; + + if (copy_from_user(dm_op, irqfd->dm_op, irqfd->size)) { + ret = -EFAULT; + goto error_kfree; + } + + kirqfd->xbufs.size = irqfd->size; + set_xen_guest_handle(kirqfd->xbufs.h, dm_op); + kirqfd->dom = irqfd->dom; + INIT_WORK(&kirqfd->shutdown, irqfd_shutdown); + + f = fdget(irqfd->fd); + if (!f.file) { + ret = -EBADF; + goto error_kfree; + } + + kirqfd->eventfd = eventfd_ctx_fileget(f.file); + if (IS_ERR(kirqfd->eventfd)) { + ret = PTR_ERR(kirqfd->eventfd); + goto error_fd_put; + } + + /* + * Install our own custom wake-up handling so we are notified via a + * callback whenever someone signals the underlying eventfd. + */ + init_waitqueue_func_entry(&kirqfd->wait, irqfd_wakeup); + init_poll_funcptr(&kirqfd->pt, irqfd_poll_func); + + mutex_lock(&irqfds_lock); + + list_for_each_entry(tmp, &irqfds_list, list) { + if (kirqfd->eventfd == tmp->eventfd) { + ret = -EBUSY; + mutex_unlock(&irqfds_lock); + goto error_eventfd; + } + } + + list_add_tail(&kirqfd->list, &irqfds_list); + mutex_unlock(&irqfds_lock); + + /* + * Check if there was an event already pending on the eventfd before we + * registered, and trigger it as if we didn't miss it. + */ + events = vfs_poll(f.file, &kirqfd->pt); + if (events & EPOLLIN) + irqfd_inject(kirqfd); + + /* + * Do not drop the file until the kirqfd is fully initialized, otherwise + * we might race against the EPOLLHUP. + */ + fdput(f); + return 0; + +error_eventfd: + eventfd_ctx_put(kirqfd->eventfd); + +error_fd_put: + fdput(f); + +error_kfree: + kfree(kirqfd); + return ret; +} + +static int privcmd_irqfd_deassign(struct privcmd_irqfd *irqfd) +{ + struct privcmd_kernel_irqfd *kirqfd; + struct eventfd_ctx *eventfd; + + eventfd = eventfd_ctx_fdget(irqfd->fd); + if (IS_ERR(eventfd)) + return PTR_ERR(eventfd); + + mutex_lock(&irqfds_lock); + + list_for_each_entry(kirqfd, &irqfds_list, list) { + if (kirqfd->eventfd == eventfd) { + irqfd_deactivate(kirqfd); + break; + } + } + + mutex_unlock(&irqfds_lock); + + eventfd_ctx_put(eventfd); + + /* + * Block until we know all outstanding shutdown jobs have completed so + * that we guarantee there will not be any more interrupts once this + * deassign function returns. + */ + flush_workqueue(irqfd_cleanup_wq); + + return 0; +} + +static long privcmd_ioctl_irqfd(struct file *file, void __user *udata) +{ + struct privcmd_data *data = file->private_data; + struct privcmd_irqfd irqfd; + + if (copy_from_user(&irqfd, udata, sizeof(irqfd))) + return -EFAULT; + + /* No other flags should be set */ + if (irqfd.flags & ~PRIVCMD_IRQFD_FLAG_DEASSIGN) + return -EINVAL; + + /* If restriction is in place, check the domid matches */ + if (data->domid != DOMID_INVALID && data->domid != irqfd.dom) + return -EPERM; + + if (irqfd.flags & PRIVCMD_IRQFD_FLAG_DEASSIGN) + return privcmd_irqfd_deassign(&irqfd); + + return privcmd_irqfd_assign(&irqfd); +} + +static int privcmd_irqfd_init(void) +{ + irqfd_cleanup_wq = alloc_workqueue("privcmd-irqfd-cleanup", 0, 0); + if (!irqfd_cleanup_wq) + return -ENOMEM; + + return 0; +} + +static void privcmd_irqfd_exit(void) +{ + struct privcmd_kernel_irqfd *kirqfd, *tmp; + + mutex_lock(&irqfds_lock); + + list_for_each_entry_safe(kirqfd, tmp, &irqfds_list, list) + irqfd_deactivate(kirqfd); + + mutex_unlock(&irqfds_lock); + + destroy_workqueue(irqfd_cleanup_wq); +} +#else +static inline long privcmd_ioctl_irqfd(struct file *file, void __user *udata) +{ + return -EOPNOTSUPP; +} + +static inline int privcmd_irqfd_init(void) +{ + return 0; +} + +static inline void privcmd_irqfd_exit(void) +{ +} +#endif /* CONFIG_XEN_PRIVCMD_IRQFD */ + static long privcmd_ioctl(struct file *file, unsigned int cmd, unsigned long data) { @@ -868,6 +1130,10 @@ static long privcmd_ioctl(struct file *file, ret = privcmd_ioctl_mmap_resource(file, udata); break; + case IOCTL_PRIVCMD_IRQFD: + ret = privcmd_ioctl_irqfd(file, udata); + break; + default: break; } @@ -992,15 +1258,27 @@ static int __init privcmd_init(void) err = misc_register(&xen_privcmdbuf_dev); if (err != 0) { pr_err("Could not register Xen hypercall-buf device\n"); - misc_deregister(&privcmd_dev); - return err; + goto err_privcmdbuf; + } + + err = privcmd_irqfd_init(); + if (err != 0) { + pr_err("irqfd init failed\n"); + goto err_irqfd; } return 0; + +err_irqfd: + misc_deregister(&xen_privcmdbuf_dev); +err_privcmdbuf: + misc_deregister(&privcmd_dev); + return err; } static void __exit privcmd_exit(void) { + privcmd_irqfd_exit(); misc_deregister(&privcmd_dev); misc_deregister(&xen_privcmdbuf_dev); } diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h index d2029556083e..375718ba4ab6 100644 --- a/include/uapi/xen/privcmd.h +++ b/include/uapi/xen/privcmd.h @@ -98,6 +98,18 @@ struct privcmd_mmap_resource { __u64 addr; }; +/* For privcmd_irqfd::flags */ +#define PRIVCMD_IRQFD_FLAG_DEASSIGN (1 << 0) + +struct privcmd_irqfd { + void __user *dm_op; + __u32 size; /* Size of structure pointed by dm_op */ + __u32 fd; + __u32 flags; + domid_t dom; + __u8 pad[2]; +}; + /* * @cmd: IOCTL_PRIVCMD_HYPERCALL * @arg: &privcmd_hypercall_t @@ -125,5 +137,7 @@ struct privcmd_mmap_resource { _IOC(_IOC_NONE, 'P', 6, sizeof(domid_t)) #define IOCTL_PRIVCMD_MMAP_RESOURCE \ _IOC(_IOC_NONE, 'P', 7, sizeof(struct privcmd_mmap_resource)) +#define IOCTL_PRIVCMD_IRQFD \ + _IOC(_IOC_NONE, 'P', 8, sizeof(struct privcmd_irqfd)) #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */ -- 2.31.1.272.g89b43f80a514

8 months, 1 week

[PATCH V4] xen: privcmd: Add support for irqfd

by Viresh Kumar

Xen provides support for injecting interrupts to the guests via the HYPERVISOR_dm_op() hypercall. The same is used by the Virtio based device backend implementations, in an inefficient manner currently. Generally, the Virtio backends are implemented to work with the Eventfd based mechanism. In order to make such backends work with Xen, another software layer needs to poll the Eventfds and raise an interrupt to the guest using the Xen based mechanism. This results in an extra context switch. This is not a new problem in Linux though. It is present with other hypervisors like KVM, etc. as well. The generic solution implemented in the kernel for them is to provide an IOCTL call to pass the interrupt details and eventfd, which lets the kernel take care of polling the eventfd and raising of the interrupt, instead of handling this in user space (which involves an extra context switch). This patch adds support to inject a specific interrupt to guest using the eventfd mechanism, by preventing the extra context switch. Inspired by existing implementations for KVM, etc.. Signed-off-by: Viresh Kumar <viresh.kumar(a)linaro.org> --- V3->V4 - Drop the imported definitions to hvm/dm_op.h. - Make the caller pass a pointer to pre-filled "struct xen_dm_op" instance and get rid of irq and level fields. - Enable the irqfd feature under a new Kconfig entry. V2->V3 - Select EVENTFD from Kconfig V1->V2: - Improve error handling. - Remove the unnecessary usage of list_for_each_entry_safe(). - Restrict the use of XEN_DMOP_set_irq_level to only ARM64. - Import definitions from Xen to hvm/dm_op.h. drivers/xen/Kconfig | 8 ++ drivers/xen/privcmd.c | 286 ++++++++++++++++++++++++++++++++++++- include/uapi/xen/privcmd.h | 14 ++ 3 files changed, 306 insertions(+), 2 deletions(-) diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index d5d7c402b651..c7fabfab4c20 100644 --- a/drivers/xen/Kconfig +++ b/drivers/xen/Kconfig @@ -269,6 +269,14 @@ config XEN_PRIVCMD disaggregated Xen setups this driver might be needed for other domains, too. +config XEN_PRIVCMD_IRQFD + bool "Xen irqfd support" + depends on XEN_PRIVCMD && XEN_VIRTIO && EVENTFD + default m + help + irqfd is a mechanism to inject a specific interrupt to a User VM using + a decoupled eventfd mechanism. + config XEN_ACPI_PROCESSOR tristate "Xen ACPI processor" depends on XEN && XEN_PV_DOM0 && X86 && ACPI_PROCESSOR && CPU_FREQ diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index e2f580e30a86..584c8de56c5e 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -9,11 +9,16 @@ #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt +#include <linux/eventfd.h> +#include <linux/file.h> #include <linux/kernel.h> #include <linux/module.h> +#include <linux/mutex.h> +#include <linux/poll.h> #include <linux/sched.h> #include <linux/slab.h> #include <linux/string.h> +#include <linux/workqueue.h> #include <linux/errno.h> #include <linux/mm.h> #include <linux/mman.h> @@ -833,6 +838,267 @@ static long privcmd_ioctl_mmap_resource(struct file *file, return rc; } +#ifdef CONFIG_XEN_PRIVCMD_IRQFD +/* Irqfd support */ +static struct workqueue_struct *irqfd_cleanup_wq; +static DEFINE_MUTEX(irqfds_lock); +static LIST_HEAD(irqfds_list); + +struct privcmd_kernel_irqfd { + struct xen_dm_op_buf xbufs; + domid_t dom; + bool error; + struct eventfd_ctx *eventfd; + struct work_struct shutdown; + wait_queue_entry_t wait; + struct list_head list; + poll_table pt; +}; + +static void irqfd_deactivate(struct privcmd_kernel_irqfd *kirqfd) +{ + lockdep_assert_held(&irqfds_lock); + + list_del_init(&kirqfd->list); + queue_work(irqfd_cleanup_wq, &kirqfd->shutdown); +} + +static void irqfd_shutdown(struct work_struct *work) +{ + struct privcmd_kernel_irqfd *kirqfd = + container_of(work, struct privcmd_kernel_irqfd, shutdown); + u64 cnt; + + eventfd_ctx_remove_wait_queue(kirqfd->eventfd, &kirqfd->wait, &cnt); + eventfd_ctx_put(kirqfd->eventfd); + kfree(kirqfd); +} + +static void irqfd_inject(struct privcmd_kernel_irqfd *kirqfd) +{ + u64 cnt; + long rc; + + eventfd_ctx_do_read(kirqfd->eventfd, &cnt); + + xen_preemptible_hcall_begin(); + rc = HYPERVISOR_dm_op(kirqfd->dom, 1, &kirqfd->xbufs); + xen_preemptible_hcall_end(); + + /* Don't repeat the error message for consecutive failures */ + if (rc && !kirqfd->error) { + pr_err("Failed to configure irq for guest domain: %d\n", + kirqfd->dom); + } + + kirqfd->error = !!rc; +} + +static int +irqfd_wakeup(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key) +{ + struct privcmd_kernel_irqfd *kirqfd = + container_of(wait, struct privcmd_kernel_irqfd, wait); + __poll_t flags = key_to_poll(key); + + if (flags & EPOLLIN) + irqfd_inject(kirqfd); + + if (flags & EPOLLHUP) { + mutex_lock(&irqfds_lock); + irqfd_deactivate(kirqfd); + mutex_unlock(&irqfds_lock); + } + + return 0; +} + +static void +irqfd_poll_func(struct file *file, wait_queue_head_t *wqh, poll_table *pt) +{ + struct privcmd_kernel_irqfd *kirqfd = + container_of(pt, struct privcmd_kernel_irqfd, pt); + + add_wait_queue_priority(wqh, &kirqfd->wait); +} + +static int privcmd_irqfd_assign(struct privcmd_irqfd *irqfd) +{ + struct privcmd_kernel_irqfd *kirqfd, *tmp; + struct eventfd_ctx *eventfd; + __poll_t events; + struct fd f; + void *dm_op; + int ret; + + kirqfd = kzalloc(sizeof(*kirqfd) + irqfd->size, GFP_KERNEL); + if (!kirqfd) + return -ENOMEM; + dm_op = kirqfd + 1; + + if (copy_from_user(dm_op, irqfd->dm_op, irqfd->size)) { + ret = -EFAULT; + goto error_kfree; + } + + kirqfd->xbufs.size = irqfd->size; + set_xen_guest_handle(kirqfd->xbufs.h, dm_op); + kirqfd->dom = irqfd->dom; + INIT_LIST_HEAD(&kirqfd->list); + INIT_WORK(&kirqfd->shutdown, irqfd_shutdown); + + f = fdget(irqfd->fd); + if (!f.file) { + ret = -EBADF; + goto error_kfree; + } + + eventfd = eventfd_ctx_fileget(f.file); + if (IS_ERR(eventfd)) { + ret = PTR_ERR(eventfd); + goto error_fd_put; + } + + kirqfd->eventfd = eventfd; + + /* + * Install our own custom wake-up handling so we are notified via a + * callback whenever someone signals the underlying eventfd. + */ + init_waitqueue_func_entry(&kirqfd->wait, irqfd_wakeup); + init_poll_funcptr(&kirqfd->pt, irqfd_poll_func); + + mutex_lock(&irqfds_lock); + + list_for_each_entry(tmp, &irqfds_list, list) { + if (kirqfd->eventfd == tmp->eventfd) { + ret = -EBUSY; + mutex_unlock(&irqfds_lock); + goto error_eventfd; + } + } + + list_add_tail(&kirqfd->list, &irqfds_list); + mutex_unlock(&irqfds_lock); + + /* + * Check if there was an event already pending on the eventfd before we + * registered, and trigger it as if we didn't miss it. + */ + events = vfs_poll(f.file, &kirqfd->pt); + if (events & EPOLLIN) + irqfd_inject(kirqfd); + + /* + * Do not drop the file until the kirqfd is fully initialized, otherwise + * we might race against the EPOLLHUP. + */ + fdput(f); + return 0; + +error_eventfd: + eventfd_ctx_put(eventfd); + +error_fd_put: + fdput(f); + +error_kfree: + kfree(kirqfd); + return ret; +} + +static int privcmd_irqfd_deassign(struct privcmd_irqfd *irqfd) +{ + struct privcmd_kernel_irqfd *kirqfd; + struct eventfd_ctx *eventfd; + + eventfd = eventfd_ctx_fdget(irqfd->fd); + if (IS_ERR(eventfd)) + return PTR_ERR(eventfd); + + mutex_lock(&irqfds_lock); + + list_for_each_entry(kirqfd, &irqfds_list, list) { + if (kirqfd->eventfd == eventfd) { + irqfd_deactivate(kirqfd); + break; + } + } + + mutex_unlock(&irqfds_lock); + + eventfd_ctx_put(eventfd); + + /* + * Block until we know all outstanding shutdown jobs have completed so + * that we guarantee there will not be any more interrupts once this + * deassign function returns. + */ + flush_workqueue(irqfd_cleanup_wq); + + return 0; +} + +static long privcmd_ioctl_irqfd(struct file *file, void __user *udata) +{ + struct privcmd_data *data = file->private_data; + struct privcmd_irqfd irqfd; + + if (copy_from_user(&irqfd, udata, sizeof(irqfd))) + return -EFAULT; + + /* No other flags should be set */ + if (irqfd.flags & ~PRIVCMD_IRQFD_FLAG_DEASSIGN) + return -EINVAL; + + /* If restriction is in place, check the domid matches */ + if (data->domid != DOMID_INVALID && data->domid != irqfd.dom) + return -EPERM; + + if (irqfd.flags & PRIVCMD_IRQFD_FLAG_DEASSIGN) + return privcmd_irqfd_deassign(&irqfd); + + return privcmd_irqfd_assign(&irqfd); +} + +static int privcmd_irqfd_init(void) +{ + irqfd_cleanup_wq = alloc_workqueue("privcmd-irqfd-cleanup", 0, 0); + if (!irqfd_cleanup_wq) + return -ENOMEM; + + return 0; +} + +static void privcmd_irqfd_exit(void) +{ + struct privcmd_kernel_irqfd *kirqfd, *tmp; + + mutex_lock(&irqfds_lock); + + list_for_each_entry_safe(kirqfd, tmp, &irqfds_list, list) + irqfd_deactivate(kirqfd); + + mutex_unlock(&irqfds_lock); + + destroy_workqueue(irqfd_cleanup_wq); +} +#else +static inline long privcmd_ioctl_irqfd(struct file *file, void __user *udata) +{ + return -EOPNOTSUPP; +} + +static inline int privcmd_irqfd_init(void) +{ + return 0; +} + +static inline void privcmd_irqfd_exit(void) +{ +} +#endif /* CONFIG_XEN_PRIVCMD_IRQFD */ + static long privcmd_ioctl(struct file *file, unsigned int cmd, unsigned long data) { @@ -868,6 +1134,10 @@ static long privcmd_ioctl(struct file *file, ret = privcmd_ioctl_mmap_resource(file, udata); break; + case IOCTL_PRIVCMD_IRQFD: + ret = privcmd_ioctl_irqfd(file, udata); + break; + default: break; } @@ -992,15 +1262,27 @@ static int __init privcmd_init(void) err = misc_register(&xen_privcmdbuf_dev); if (err != 0) { pr_err("Could not register Xen hypercall-buf device\n"); - misc_deregister(&privcmd_dev); - return err; + goto err_privcmdbuf; + } + + err = privcmd_irqfd_init(); + if (err != 0) { + pr_err("irqfd init failed\n"); + goto err_irqfd; } return 0; + +err_irqfd: + misc_deregister(&xen_privcmdbuf_dev); +err_privcmdbuf: + misc_deregister(&privcmd_dev); + return err; } static void __exit privcmd_exit(void) { + privcmd_irqfd_exit(); misc_deregister(&privcmd_dev); misc_deregister(&xen_privcmdbuf_dev); } diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h index d2029556083e..375718ba4ab6 100644 --- a/include/uapi/xen/privcmd.h +++ b/include/uapi/xen/privcmd.h @@ -98,6 +98,18 @@ struct privcmd_mmap_resource { __u64 addr; }; +/* For privcmd_irqfd::flags */ +#define PRIVCMD_IRQFD_FLAG_DEASSIGN (1 << 0) + +struct privcmd_irqfd { + void __user *dm_op; + __u32 size; /* Size of structure pointed by dm_op */ + __u32 fd; + __u32 flags; + domid_t dom; + __u8 pad[2]; +}; + /* * @cmd: IOCTL_PRIVCMD_HYPERCALL * @arg: &privcmd_hypercall_t @@ -125,5 +137,7 @@ struct privcmd_mmap_resource { _IOC(_IOC_NONE, 'P', 6, sizeof(domid_t)) #define IOCTL_PRIVCMD_MMAP_RESOURCE \ _IOC(_IOC_NONE, 'P', 7, sizeof(struct privcmd_mmap_resource)) +#define IOCTL_PRIVCMD_IRQFD \ + _IOC(_IOC_NONE, 'P', 8, sizeof(struct privcmd_irqfd)) #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */ -- 2.31.1.272.g89b43f80a514

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Stratos-dev August 2023