[PATCH v9 26/27] virt: gunyah: Add irqfd interface

Elliot Berman
2023-01-20T23:23:49Z

Enable support for creating irqfds which can raise an interrupt on a
Gunyah virtual machine. irqfds are exposed to userspace as a Gunyah VM
function with the name "irqfd". If the VM devicetree is not configured
to create a doorbell with the corresponding label, userspace will still
be able to assert the eventfd but no interrupt will be raised on the
guest.

Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
Documentation/virt/gunyah/vm-manager.rst | 22 +++
drivers/virt/gunyah/Kconfig | 9 ++
drivers/virt/gunyah/Makefile | 1 +
drivers/virt/gunyah/gunyah_irqfd.c | 166 +++++++++++++++++++++++
include/linux/gunyah.h | 5 +
include/uapi/linux/gunyah.h | 11 +-
6 files changed, 213 insertions(+), 1 deletion(-)
create mode 100644 drivers/virt/gunyah/gunyah_irqfd.c

diff --git a/Documentation/virt/gunyah/vm-manager.rst b/Documentation/virt/gunyah/vm-manager.rst
index d11267d59802..b6cf8db826b8 100644
--- a/Documentation/virt/gunyah/vm-manager.rst
+++ b/Documentation/virt/gunyah/vm-manager.rst
@@ -142,3 +142,25 @@ The vcpu type will register with the VM Manager to expect to control
vCPU number `vcpu_id`. It returns a file descriptor allowing interaction with
the vCPU. See the Gunyah vCPU API description sections for interacting with
the Gunyah vCPU file descriptors.
+
+Type: "irqfd"
+^^^^^^^^^^^^^
+
+::
+
+ struct gh_fn_irqfd_arg {
+ __u32 fd;
+ __u32 label;
+ #define GH_IRQFD_LEVEL (1UL << 0)
+ #define GH_IRQFD_DEASSIGN (1UL << 1)
+ __u32 flags;
+ };
+
+Allows setting an eventfd to directly trigger a guest interrupt.
+irqfd.fd specifies the file descriptor to use as the eventfd.
+irqfd.label corresponds to the doorbell label used in the guest VM's devicetree.
+The irqfd is removed using the GH_IRQFD_DEASSIGN flag and specifying at least
+the irqfd.label.
+
+GH_IRQFD_LEVEL configures the corresponding doorbell to behave like a level
+triggered interrupt.
diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
index 4c1c6110b50e..2cde24d429d1 100644
--- a/drivers/virt/gunyah/Kconfig
+++ b/drivers/virt/gunyah/Kconfig
@@ -26,3 +26,12 @@ config GUNYAH_VCPU
VMMs can also handle stage 2 faults of the vCPUs.

Say Y/M here if unsure and you want to support Gunyah VMMs.
+
+config GUNYAH_IRQFD
+ tristate "Gunyah irqfd interface"
+ depends on GUNYAH
+ help
+ Enable kernel support for creating irqfds which can raise an interrupt
+ on Gunyah virtual machine.
+
+ Say Y/M here if unsure and you want to support Gunyah VMMs.
diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
index 2d1b604a7b03..6cf756bfa3c2 100644
--- a/drivers/virt/gunyah/Makefile
+++ b/drivers/virt/gunyah/Makefile
@@ -7,3 +7,4 @@ gunyah_rsc_mgr-y += rsc_mgr.o rsc_mgr_rpc.o vm_mgr.o vm_mgr_mm.o
obj-$(CONFIG_GUNYAH) += gunyah_rsc_mgr.o

obj-$(CONFIG_GUNYAH_VCPU) += gunyah_vcpu.o
+obj-$(CONFIG_GUNYAH_IRQFD) += gunyah_irqfd.o
diff --git a/drivers/virt/gunyah/gunyah_irqfd.c b/drivers/virt/gunyah/gunyah_irqfd.c
new file mode 100644
index 000000000000..a3be9ca2377a
--- /dev/null
+++ b/drivers/virt/gunyah/gunyah_irqfd.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/eventfd.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/gunyah.h>
+#include <linux/gunyah_vm_mgr.h>
+#include <linux/kref.h>
+#include <linux/module.h>
+#include <linux/poll.h>
+#include <linux/printk.h>
+
+#include <uapi/linux/gunyah.h>
+
+struct gunyah_irqfd {
+ struct gunyah_resource *ghrsc;
+ struct gunyah_vm_resource_ticket ticket;
+ struct gunyah_vm_function *f;
+
+ struct kref kref;
+ bool level;
+
+ struct eventfd_ctx *ctx;
+ wait_queue_entry_t wait;
+ poll_table pt;
+ struct fd fd;
+};
+
+static void gh_irqfd_cleanup(struct kref *kref)
+{
+ struct gunyah_irqfd *irqfd = container_of(kref, struct gunyah_irqfd, kref);
+
+ kfree(irqfd);
+}
+
+static int irqfd_wakeup(wait_queue_entry_t *wait, unsigned int mode, int sync, void *key)
+{
+ struct gunyah_irqfd *irqfd = container_of(wait, struct gunyah_irqfd, wait);
+ __poll_t flags = key_to_poll(key);
+ u64 enable_mask = GH_DBL_NONBLOCK;
+ u64 old_flags;
+ int ret = 0;
+
+ if (flags & EPOLLIN) {
+ if (irqfd->ghrsc) {
+ ret = gh_hypercall_dbl_send(irqfd->ghrsc->capid, enable_mask, &old_flags);
+ if (ret)
+ pr_err("Failed to assert irq %d\n", irqfd->f->fn.irqfd.label);
+ }
+ }
+
+ return 0;
+}
+
+static void irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh, poll_table *pt)
+{
+ struct gunyah_irqfd *irq_ctx = container_of(pt, struct gunyah_irqfd, pt);
+
+ add_wait_queue(wqh, &irq_ctx->wait);
+}
+
+static int gunyah_irqfd_populate(struct gunyah_vm_resource_ticket *ticket,
+ struct gunyah_resource *ghrsc)
+{
+ struct gunyah_irqfd *irqfd = container_of(ticket, struct gunyah_irqfd, ticket);
+ u64 enable_mask = GH_DBL_NONBLOCK;
+ u64 ack_mask = ~0;
+ int ret = 0;
+
+ irqfd->ghrsc = ghrsc;
+ if (irqfd->level) {
+ ret = gh_hypercall_dbl_set_mask(irqfd->ghrsc->capid, enable_mask, ack_mask);
+ if (ret)
+ pr_warn("irq %d couldn't be set as level triggered. Might cause IRQ storm if asserted\n",
+ irqfd->f->fn.irqfd.label);
+ }
+ kref_get(&irqfd->kref);
+
+ return 0;
+}
+
+static void gunyah_irqfd_unpopulate(struct gunyah_vm_resource_ticket *ticket,
+ struct gunyah_resource *ghrsc)
+{
+ struct gunyah_irqfd *irqfd = container_of(ticket, struct gunyah_irqfd, ticket);
+ u64 cnt;
+
+ eventfd_ctx_remove_wait_queue(irqfd->ctx, &irqfd->wait, &cnt);
+ eventfd_ctx_put(irqfd->ctx);
+ fdput(irqfd->fd);
+ irqfd->ctx = NULL;
+ irqfd->fd.file = NULL;
+ irqfd->ghrsc = NULL;
+ kref_put(&irqfd->kref, gh_irqfd_cleanup);
+}
+
+static long gunyah_irqfd_bind(struct gunyah_vm_function *f)
+{
+ __poll_t events;
+ struct gunyah_irqfd *irqfd;
+ long r;
+
+ irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
+ if (!irqfd)
+ return -ENOMEM;
+
+ irqfd->f = f;
+ f->data = irqfd;
+
+ irqfd->fd = fdget(f->fn.irqfd.fd);
+ if (!irqfd->fd.file) {
+ r = -EBADF;
+ goto err_free;
+ }
+
+ irqfd->ctx = eventfd_ctx_fileget(irqfd->fd.file);
+ if (IS_ERR(irqfd->ctx)) {
+ r = PTR_ERR(irqfd->ctx);
+ goto err_fdput;
+ }
+
+ if (f->fn.irqfd.flags & GH_IRQFD_LEVEL)
+ irqfd->level = true;
+
+ init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
+ init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
+ kref_init(&irqfd->kref);
+
+ irqfd->ticket.resource_type = GUNYAH_RESOURCE_TYPE_BELL_TX;
+ irqfd->ticket.label = f->fn.irqfd.label;
+ irqfd->ticket.owner = THIS_MODULE;
+ irqfd->ticket.populate = gunyah_irqfd_populate;
+ irqfd->ticket.unpopulate = gunyah_irqfd_unpopulate;
+
+ r = ghvm_add_resource_ticket(f->ghvm, &irqfd->ticket);
+ if (r)
+ goto err_ctx;
+
+ events = vfs_poll(irqfd->fd.file, &irqfd->pt);
+ if (events & EPOLLIN)
+ pr_warn("Premature injection of interrupt\n");
+
+ return 0;
+err_ctx:
+ eventfd_ctx_put(irqfd->ctx);
+err_fdput:
+ fdput(irqfd->fd);
+err_free:
+ kfree(irqfd);
+ return r;
+}
+
+static void gunyah_irqfd_release(struct gunyah_vm_function *f)
+{
+ struct gunyah_irqfd *irqfd = f->data;
+
+ /* unpopulate will trigger clean up of the eventfd */
+ ghvm_remove_resource_ticket(irqfd->f->ghvm, &irqfd->ticket);
+}
+
+DECLARE_GUNYAH_VM_FUNCTION_INIT(irqfd, gunyah_irqfd_bind, gunyah_irqfd_release);
+MODULE_DESCRIPTION("Gunyah irqfds");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
index ac4879940c10..6b363707a901 100644
--- a/include/linux/gunyah.h
+++ b/include/linux/gunyah.h
@@ -33,6 +33,11 @@ struct gunyah_resource {
u32 rm_label;
};

+/**
+ * Gunyah Doorbells
+ */
+#define GH_DBL_NONBLOCK BIT(32)
+
/**
* Gunyah Message Queues
*/
diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index b4afb11f538a..a947f0317ca9 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h
@@ -57,10 +57,19 @@ struct gh_fn_vcpu_arg {
__u32 vcpu_id;
};

+struct gh_fn_irqfd_arg {
+ __u32 fd;
+ __u32 label;
+#define GH_IRQFD_LEVEL (1UL << 0)
+#define GH_IRQFD_DEASSIGN (1UL << 1)
+ __u32 flags;
+};
+
struct gh_vm_function {
char name[GUNYAH_FUNCTION_NAME_SIZE];
union {
- struct gh_device_vcpu_arg vcpu;
+ struct gh_fn_vcpu_arg vcpu;
+ struct gh_fn_irqfd_arg irqfd;
char data[GUNYAH_FUNCTION_MAX_ARG_SIZE];
};
};
--
2.39.0