On 3/3/23 7:06 PM, Elliot Berman wrote:
Allow userspace to attach an ioeventfd to an mmio address within the guest.
Co-developed-by: Prakruthi Deepak Heragu <quic_pheragu@xxxxxxxxxxx>
Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@xxxxxxxxxxx>
Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
Mostly minor suggestions here. -Alex
---
Documentation/virt/gunyah/vm-manager.rst | 2 +-
drivers/virt/gunyah/Kconfig | 9 ++
drivers/virt/gunyah/Makefile | 1 +
drivers/virt/gunyah/gunyah_ioeventfd.c | 117 +++++++++++++++++++++++
include/uapi/linux/gunyah.h | 37 +++++++
5 files changed, 165 insertions(+), 1 deletion(-)
create mode 100644 drivers/virt/gunyah/gunyah_ioeventfd.c
diff --git a/Documentation/virt/gunyah/vm-manager.rst b/Documentation/virt/gunyah/vm-manager.rst
index a1dd70f0cbf6..cd41a705849f 100644
--- a/Documentation/virt/gunyah/vm-manager.rst
+++ b/Documentation/virt/gunyah/vm-manager.rst
@@ -124,7 +124,7 @@ the VM starts.
The possible types are documented below:
.. kernel-doc:: include/uapi/linux/gunyah.h
- :identifiers: GH_FN_VCPU gh_fn_vcpu_arg GH_FN_IRQFD gh_fn_irqfd_arg
+ :identifiers: GH_FN_VCPU gh_fn_vcpu_arg GH_FN_IRQFD gh_fn_irqfd_arg GH_FN_IOEVENTFD gh_fn_ioeventfd_arg
Gunyah VCPU API Descriptions
----------------------------
diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
index 2cde24d429d1..bd8e31184962 100644
--- a/drivers/virt/gunyah/Kconfig
+++ b/drivers/virt/gunyah/Kconfig
@@ -35,3 +35,12 @@ config GUNYAH_IRQFD
on Gunyah virtual machine.
Say Y/M here if unsure and you want to support Gunyah VMMs.
+
+config GUNYAH_IOEVENTFD
+ tristate "Gunyah ioeventfd interface"
+ depends on GUNYAH
+ help
+ Enable kernel support for creating ioeventfds which can alert userspace
+ when a Gunyah virtual machine accesses a memory address.
+
+ 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 6cf756bfa3c2..7347b1470491 100644
--- a/drivers/virt/gunyah/Makefile
+++ b/drivers/virt/gunyah/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_GUNYAH) += gunyah_rsc_mgr.o
obj-$(CONFIG_GUNYAH_VCPU) += gunyah_vcpu.o
obj-$(CONFIG_GUNYAH_IRQFD) += gunyah_irqfd.o
+obj-$(CONFIG_GUNYAH_IOEVENTFD) += gunyah_ioeventfd.o
diff --git a/drivers/virt/gunyah/gunyah_ioeventfd.c b/drivers/virt/gunyah/gunyah_ioeventfd.c
new file mode 100644
index 000000000000..517f55706ed9
--- /dev/null
+++ b/drivers/virt/gunyah/gunyah_ioeventfd.c
@@ -0,0 +1,117 @@
+// 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/module.h>
+#include <linux/printk.h>
+
+#include <uapi/linux/gunyah.h>
+
+struct gh_ioeventfd {
+ struct gh_vm_function_instance *f;
+ struct gh_vm_io_handler io_handler;
+
+ struct eventfd_ctx *ctx;
+};
+
+static int gh_write_ioeventfd(struct gh_vm_io_handler *io_dev, u64 addr, u32 len, u64 data)
+{
+ struct gh_ioeventfd *iofd = container_of(io_dev, struct gh_ioeventfd, io_handler);
+
I think it's interesting that this signals an event even if
len is zero. I'm not saying it's wrong, just interesting...
+ eventfd_signal(iofd->ctx, 1);
+ return 0;
+}
+
+static struct gh_vm_io_handler_ops io_ops = {
+ .write = gh_write_ioeventfd,
+};
+
+static long gh_ioeventfd_bind(struct gh_vm_function_instance *f)
+{
+ const struct gh_fn_ioeventfd_arg *args = f->argp;
+ struct eventfd_ctx *ctx = NULL;
No need to initialize ctx.
+ struct gh_ioeventfd *iofd;
+ int ret;
+
+ if (f->arg_size != sizeof(*args))
+ return -EINVAL;
+
+ /* must be natural-word sized, or 0 to ignore length */
+ switch (args->len) {
+ case 0:
+ case 1:
+ case 2:
+ case 4:
+ case 8:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* check for range overflow */
+ if (args->addr + args->len < args->addr)
I think you could use:
if (overflows_type(args->addr + args->len, args->addr))
This is a relatively recent addition (and I haven't been using it
myself yet) but it's meant for this purpose. Consider using it
and its relatives here and anywhere else you're making this kind
of check.
+ return -EINVAL;
+
+ /* ioeventfd with no length can't be combined with DATAMATCH */
+ if (!args->len && (args->flags & GH_IOEVENTFD_DATAMATCH))
+ return -EINVAL;
+
Maybe check for invalid flags before before ensuring
valid flags are used properly?
+ /* All other flag bits are reserved for future use */
+ if (args->flags & ~GH_IOEVENTFD_DATAMATCH)
+ return -EINVAL;
+
+ ctx = eventfd_ctx_fdget(args->fd);
+ if (IS_ERR(ctx))
+ return PTR_ERR(ctx);
+
+ iofd = kzalloc(sizeof(*iofd), GFP_KERNEL);
+ if (!iofd) {
+ ret = -ENOMEM;
+ goto err_eventfd;
+ }
+
+ f->data = iofd;
+ iofd->f = f;
+
+ iofd->ctx = ctx;
+
+ if (args->flags & GH_IOEVENTFD_DATAMATCH) {
+ iofd->io_handler.datamatch = true;
+ iofd->io_handler.len = args->len;
+ iofd->io_handler.data = args->datamatch;
I think you might want to rename one or the other of these
fields (datamatch or data). I might be wrong; I'll explain
elsewhere what I mean.
+ }
+ iofd->io_handler.addr = args->addr;
+ iofd->io_handler.ops = &io_ops;
+
+ ret = gh_vm_add_io_handler(f->ghvm, &iofd->io_handler);
+ if (ret)
+ goto err_io_dev_add;
+
+ return 0;
+
+err_io_dev_add:
+ kfree(iofd);
+err_eventfd:
+ eventfd_ctx_put(ctx);
+ return ret;
+}
+
+static void gh_ioevent_unbind(struct gh_vm_function_instance *f)
+{
+ struct gh_ioeventfd *iofd = f->data;
+
+ eventfd_ctx_put(iofd->ctx);
It's not a big deal but I prefer to "undo" everything in the
reverse order that they are originally "done". I.e., put the
eventfd context after removing the I/O handler.
+ gh_vm_remove_io_handler(iofd->f->ghvm, &iofd->io_handler);
+ kfree(iofd);
+}
+
+DECLARE_GH_VM_FUNCTION_INIT(ioeventfd, GH_FN_IOEVENTFD,
+ gh_ioeventfd_bind, gh_ioevent_unbind);
+MODULE_DESCRIPTION("Gunyah ioeventfds");
s/ioeventfds/ioeventfd/
I understand why you might want it to be plural, but I think it's
better to just name the abstraction. (If you take this suggestion,
check elsewhere and be consistent.)
AND/OR... You might also somehow incorporate the fact that this is a
VM *function* that is represented: "Gunyah ioeventfd VM function(s)"
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index 5617dadc1c7b..f8482ff4cc55 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h
@@ -89,6 +89,23 @@ struct gh_vm_dtb_config {
*/
#define GH_FN_IRQFD 2
+/**
+ * GH_FN_IOEVENTFD - register ioeventfd to trigger when VM faults on parameter
What does "faults on parameter" mean?
+ *
+ * gh_fn_desc is filled with gh_fn_ioeventfd_arg
+ *
+ * Attaches an ioeventfd to a legal mmio address within the guest. A guest write
+ * in the registered address will signal the provided event instead of triggering
+ * an exit on the GH_VCPU_RUN ioctl.
+ *
+ * If GH_IOEVENTFD_DATAMATCH flag is set, the event will be signaled only if the
+ * written value to the registered address is equal to datamatch in
+ * struct gh_fn_ioeventfd_arg.
+ *
+ * Return: 0
+ */
+#define GH_FN_IOEVENTFD 3
If you added another tab before 3, it will align more nicely with the
next definition. (If you do that, add a tab in the other function
definitions as well.)
+
#define GH_FN_MAX_ARG_SIZE 256
/**
@@ -118,6 +135,26 @@ struct gh_fn_irqfd_arg {
#define GH_IOEVENTFD_DATAMATCH (1UL << 0)
+/**
+ * struct gh_fn_ioeventfd_arg - Arguments to create an ioeventfd function
+ * @datamatch: data used when GH_IOEVENTFD_DATAMATCH is set
+ * @addr: Address in guest memory
+ * @len: Length of access
+ * @fd: When ioeventfd is matched, this eventfd is written
+ * @flags: If GH_IOEVENTFD_DATAMATCH flag is set, the event will be signaled
+ * only if the written value to the registered address is equal to
+ * @datamatch
+ * @padding: padding bytes
+ */
+struct gh_fn_ioeventfd_arg {
+ __u64 datamatch;
+ __u64 addr; /* legal mmio address */
+ __u32 len; /* 1, 2, 4, or 8 bytes; or 0 to ignore length */
+ __s32 fd;
+ __u32 flags;
+ __u32 padding;
+};
+
/**
* struct gh_fn_desc - Arguments to create a VM function
* @type: Type of the function. See GH_FN_* macro for supported types
