Re: [PATCH v13 23/24] virt: gunyah: Add ioeventfd
From: Elliot Berman
Date: Fri Jun 09 2023 - 13:34:13 EST
On 6/5/2023 12:50 PM, Alex Elder wrote:
On 5/9/23 3:48 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>
Looks good. One question below.
Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
Thanks!
---
Documentation/virt/gunyah/vm-manager.rst | 2 +-
drivers/virt/gunyah/Kconfig | 9 ++
drivers/virt/gunyah/Makefile | 1 +
drivers/virt/gunyah/gunyah_ioeventfd.c | 130 +++++++++++++++++++++++
include/uapi/linux/gunyah.h | 37 +++++++
5 files changed, 178 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 c4960948c779..87838c5b5945 100644
--- a/Documentation/virt/gunyah/vm-manager.rst
+++ b/Documentation/virt/gunyah/vm-manager.rst
@@ -115,7 +115,7 @@ the VM *before* the VM starts.
The argument types are documented below:
.. kernel-doc:: include/uapi/linux/gunyah.h
- :identifiers: gh_fn_vcpu_arg gh_fn_irqfd_arg gh_irqfd_flags
+ :identifiers: gh_fn_vcpu_arg gh_fn_irqfd_arg gh_irqfd_flags
gh_fn_ioeventfd_arg gh_ioeventfd_flags
Gunyah VCPU API Descriptions
----------------------------
diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
index bc2c46d9df94..63bebc5b9f82 100644
--- a/drivers/virt/gunyah/Kconfig
+++ b/drivers/virt/gunyah/Kconfig
@@ -48,3 +48,12 @@ 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 ad212a1cf967..63ca11e74796 100644
--- a/drivers/virt/gunyah/Makefile
+++ b/drivers/virt/gunyah/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_GUNYAH) += gunyah.o
obj-$(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..5b1b9fd9ac3a
--- /dev/null
+++ b/drivers/virt/gunyah/gunyah_ioeventfd.c
@@ -0,0 +1,130 @@
+// 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);
Does a write of 0 bytes still signal an event?
From gunyah_ioeventfd perspective, yes. I don't think a write of 0
bytes is possible, but maybe you are thinking of scenario I'm not?
+
+ 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 gh_ioeventfd *iofd;
+ struct eventfd_ctx *ctx;
+ int ret;
+
+ if (f->arg_size != sizeof(*args))
+ return -EINVAL;
+
+ /* All other flag bits are reserved for future use */
+ if (args->flags & ~GH_IOEVENTFD_FLAGS_DATAMATCH)
+ 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 (overflows_type(args->addr + args->len, u64))
+ return -EINVAL;
+
+ /* ioeventfd with no length can't be combined with DATAMATCH */
+ if (!args->len && (args->flags & GH_IOEVENTFD_FLAGS_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_FLAGS_DATAMATCH) {
+ iofd->io_handler.datamatch = true;
+ iofd->io_handler.len = args->len;
+ iofd->io_handler.data = args->datamatch;
+ }
+ 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);
+ gh_vm_remove_io_handler(iofd->f->ghvm, &iofd->io_handler);
+ kfree(iofd);
+}
+
+static bool gh_ioevent_compare(const struct gh_vm_function_instance *f,
+ const void *arg, size_t size)
+{
+ const struct gh_fn_ioeventfd_arg *instance = f->argp,
+ *other = arg;
+
+ if (sizeof(*other) != size)
+ return false;
+
+ return instance->addr == other->addr;
+}
+
+DECLARE_GH_VM_FUNCTION_INIT(ioeventfd, GH_FN_IOEVENTFD, 3,
+ gh_ioeventfd_bind, gh_ioevent_unbind,
+ gh_ioevent_compare);
+MODULE_DESCRIPTION("Gunyah ioeventfd VM Function");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index 0c480c622686..fa1cae7419d2 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h
@@ -79,10 +79,13 @@ struct gh_vm_dtb_config {
* Return: file descriptor to manipulate the vcpu.
* @GH_FN_IRQFD: register eventfd to assert a Gunyah doorbell
* &struct gh_fn_desc.arg is a pointer to &struct
gh_fn_irqfd_arg
+ * @GH_FN_IOEVENTFD: register ioeventfd to trigger when VM faults on
parameter
+ * &struct gh_fn_desc.arg is a pointer to &struct
gh_fn_ioeventfd_arg
*/
enum gh_fn_type {
GH_FN_VCPU = 1,
GH_FN_IRQFD,
+ GH_FN_IOEVENTFD,
};
#define GH_FN_MAX_ARG_SIZE 256
@@ -134,6 +137,40 @@ struct gh_fn_irqfd_arg {
__u32 padding;
};
+/**
+ * enum gh_ioeventfd_flags - flags for use in gh_fn_ioeventfd_arg
+ * @GH_IOEVENTFD_FLAGS_DATAMATCH: the event will be signaled only if the
+ * written value to the registered
address is
+ * equal to &struct
gh_fn_ioeventfd_arg.datamatch
+ */
+enum gh_ioeventfd_flags {
+ GH_IOEVENTFD_FLAGS_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: See &enum gh_ioeventfd_flags
+ * @padding: padding bytes
+ *
+ * Create this function with &GH_VM_ADD_FUNCTION using type
&GH_FN_IOEVENTFD.
+ *
+ * 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.
+ */
+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 &enum gh_fn_type.