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Subject[PATCH v8 28/28] virt: gunyah: Add ioeventfd
Date
Allow userspace to attach an ioeventfd to an mmio address within 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 | 21 +++++
drivers/virt/gunyah/Kconfig | 10 +++
drivers/virt/gunyah/Makefile | 1 +
drivers/virt/gunyah/gunyah_ioeventfd.c | 109 +++++++++++++++++++++++
include/uapi/linux/gunyah.h | 10 +++
5 files changed, 151 insertions(+)
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 b6cf8db826b8..19ec859a7912 100644
--- a/Documentation/virt/gunyah/vm-manager.rst
+++ b/Documentation/virt/gunyah/vm-manager.rst
@@ -164,3 +164,24 @@ the irqfd.label.

GH_IRQFD_LEVEL configures the corresponding doorbell to behave like a level
triggered interrupt.
+
+Type: "ioeventfd"
+^^^^^^^^^^^^^^^^^
+
+::
+
+ struct gh_fn_ioeventfd_arg {
+ __u64 datamatch;
+ __u64 addr; /* legal mmio address */
+ __u32 len; /* 1, 2, 4, or 8 bytes */
+ __s32 fd;
+ #define GH_IOEVENTFD_DATAMATCH (1UL << 0)
+ __u32 flags;
+ };
+
+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 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.
diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
index 42842e755a04..06f1082f98f0 100644
--- a/drivers/virt/gunyah/Kconfig
+++ b/drivers/virt/gunyah/Kconfig
@@ -59,5 +59,15 @@ config GUNYAH_IRQFD
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.
+
+config GUNYAH_IOEVENTFD
+ tristate "Gunyah ioeventfd interface"
+ depends on GUNYAH_RESOURCE_MANAGER
+ depends on GUNYAH_VM_MANAGER
+ 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.
endif
diff --git a/drivers/virt/gunyah/Makefile b/drivers/virt/gunyah/Makefile
index 065eeb060597..bcffb99eb28f 100644
--- a/drivers/virt/gunyah/Makefile
+++ b/drivers/virt/gunyah/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_GUNYAH_RESOURCE_MANAGER) += 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..5f43057eb768
--- /dev/null
+++ b/drivers/virt/gunyah/gunyah_ioeventfd.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022 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 gunyah_ioeventfd {
+ struct gunyah_vm_function *f;
+ struct gunyah_vm_io_handler io_handler;
+
+ struct eventfd_ctx *ctx;
+};
+
+static int gh_write_ioeventfd(struct gunyah_vm_io_handler *io_dev, u64 addr, u32 len, u64 data)
+{
+ struct gunyah_ioeventfd *iofd = container_of(io_dev, struct gunyah_ioeventfd, io_handler);
+
+ eventfd_signal(iofd->ctx, 1);
+ return 0;
+}
+
+static struct gunyah_vm_io_handler_ops io_ops = {
+ .write = gh_write_ioeventfd,
+};
+
+static long gunyah_ioeventfd_bind(struct gunyah_vm_function *f)
+{
+ struct eventfd_ctx *ctx = NULL;
+ struct gunyah_ioeventfd *iofd;
+ const struct gh_fn_ioeventfd_arg *args = &f->fn.ioeventfd;
+ int ret;
+
+ /* 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)
+ return -EINVAL;
+
+ /* ioeventfd with no length can't be combined with DATAMATCH */
+ if (!args->len && (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;
+ }
+ iofd->io_handler.addr = args->addr;
+ iofd->io_handler.ops = &io_ops;
+
+ ret = gh_vm_mgr_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 gunyah_ioeventfd_release(struct gunyah_vm_function *f)
+{
+ struct gunyah_ioeventfd *iofd = f->data;
+
+ eventfd_ctx_put(iofd->ctx);
+ gh_vm_mgr_remove_io_handler(iofd->f->ghvm, &iofd->io_handler);
+ kfree(iofd);
+}
+
+DECLARE_GUNYAH_VM_FUNCTION_INIT(ioeventfd, gunyah_ioeventfd_bind, gunyah_ioeventfd_release);
+MODULE_DESCRIPTION("Gunyah ioeventfds");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/gunyah.h b/include/uapi/linux/gunyah.h
index 5eab212c7bf5..5da9fb933bae 100644
--- a/include/uapi/linux/gunyah.h
+++ b/include/uapi/linux/gunyah.h
@@ -65,11 +65,21 @@ struct gh_fn_irqfd_arg {
__u32 flags;
};

+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;
+#define GH_IOEVENTFD_DATAMATCH (1UL << 0)
+ __u32 flags;
+};
+
struct gh_vm_function {
char name[GUNYAH_FUNCTION_NAME_SIZE];
union {
struct gh_fn_vcpu_arg vcpu;
struct gh_fn_irqfd_arg irqfd;
+ struct gh_fn_ioeventfd_arg ioeventfd;
char data[GUNYAH_FUNCTION_MAX_ARG_SIZE];
};
};
--
2.25.1
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