[PATCH v2 09/16] KVM: device: Add test device

[Charlie Jenkins via B4 Relay <devnull+thecharlesjenkins.gmail.com@kernel.org>]

From: Charlie Jenkins <thecharlesjenkins@gmail.com>

Create a KVM test device to help verify mmio reads and write emulation.
This is a simple device that will store the data in a buffer on writes
and echo back that stored data on a read.

Signed-off-by: Charlie Jenkins <thecharlesjenkins@gmail.com>
---
 include/uapi/linux/kvm.h |  2 +
 lib/Kconfig.debug        |  6 +++
 virt/kvm/Kconfig.debug   | 16 ++++++++
 virt/kvm/Makefile.kvm    |  1 +
 virt/kvm/kvm_main.c      |  8 ++++
 virt/kvm/mmio_test.c     | 95 ++++++++++++++++++++++++++++++++++++++++++++++++
 virt/kvm/mmio_test.h     | 18 +++++++++
 7 files changed, 146 insertions(+)

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 6c8afa2047bf..abbbf74627a2 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1235,6 +1235,8 @@ enum kvm_device_type {
 #define KVM_DEV_TYPE_LOONGARCH_DMSINTC	KVM_DEV_TYPE_LOONGARCH_DMSINTC
 	KVM_DEV_TYPE_ARM_VGIC_V5,
 #define KVM_DEV_TYPE_ARM_VGIC_V5	KVM_DEV_TYPE_ARM_VGIC_V5
+	KVM_DEV_TYPE_TEST,
+#define KVM_DEV_TYPE_TEST		KVM_DEV_TYPE_TEST
 
 	KVM_DEV_TYPE_MAX,
 
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8ff5adcfe1e0..0d235bdc94ec 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -754,6 +754,12 @@ source "net/Kconfig.debug"
 
 endmenu # "Networking Debugging"
 
+menu "KVM Debugging"
+
+source "virt/kvm/Kconfig.debug"
+
+endmenu # "KVM Debugging"
+
 menu "Memory Debugging"
 
 source "mm/Kconfig.debug"
diff --git a/virt/kvm/Kconfig.debug b/virt/kvm/Kconfig.debug
new file mode 100644
index 000000000000..d24709f5bcbf
--- /dev/null
+++ b/virt/kvm/Kconfig.debug
@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config KVM_MMIO_TEST
+       bool "Enable kvm mmio testing"
+       depends on KVM
+       depends on KVM_MMIO
+       default n
+       help
+         Enable testing for kvm mmio. This is a test-only mmio device that
+         stores writes in a buffer and returns the buffered data on a read.
+         
+         This is useful for testing the kvm mmio emulation code. Enabling
+         this does not run any tests, just builds in the support for the test
+         device into the kernel.
+
+         If unsure, say N.
diff --git a/virt/kvm/Makefile.kvm b/virt/kvm/Makefile.kvm
index d047d4cf58c9..bd4da8c23923 100644
--- a/virt/kvm/Makefile.kvm
+++ b/virt/kvm/Makefile.kvm
@@ -8,6 +8,7 @@ KVM ?= ../../../virt/kvm
 kvm-y := $(KVM)/kvm_main.o $(KVM)/eventfd.o $(KVM)/binary_stats.o
 kvm-$(CONFIG_KVM_VFIO) += $(KVM)/vfio.o
 kvm-$(CONFIG_KVM_MMIO) += $(KVM)/coalesced_mmio.o
+kvm-$(CONFIG_KVM_MMIO_TEST) += $(KVM)/mmio_test.o
 kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o
 kvm-$(CONFIG_HAVE_KVM_IRQ_ROUTING) += $(KVM)/irqchip.o
 kvm-$(CONFIG_HAVE_KVM_DIRTY_RING) += $(KVM)/dirty_ring.o
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 881f92d7a469..d9bbe570eddd 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -58,6 +58,7 @@
 #include "async_pf.h"
 #include "kvm_mm.h"
 #include "vfio.h"
+#include "mmio_test.h"
 
 #include <trace/events/ipi.h>
 
@@ -6532,6 +6533,10 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
 	if (WARN_ON_ONCE(r))
 		goto err_vfio;
 
+	r = kvm_mmio_test_ops_init();
+	if (WARN_ON_ONCE(r))
+		goto err_mmio_test;
+
 	r = kvm_gmem_init(module);
 	if (r)
 		goto err_gmem;
@@ -6559,6 +6564,8 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
 err_gmem:
 	kvm_vfio_ops_exit();
 err_vfio:
+	kvm_mmio_test_ops_exit();
+err_mmio_test:
 	kvm_async_pf_deinit();
 err_async_pf:
 	kvm_irqfd_exit();
@@ -6589,6 +6596,7 @@ void kvm_exit(void)
 		free_cpumask_var(per_cpu(cpu_kick_mask, cpu));
 	kmem_cache_destroy(kvm_vcpu_cache);
 	kvm_gmem_exit();
+	kvm_mmio_test_ops_exit();
 	kvm_vfio_ops_exit();
 	kvm_async_pf_deinit();
 	kvm_irqfd_exit();
diff --git a/virt/kvm/mmio_test.c b/virt/kvm/mmio_test.c
new file mode 100644
index 000000000000..fa84c2b4c5fc
--- /dev/null
+++ b/virt/kvm/mmio_test.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * mmio_test.c - Kernel module side for testing the KVM riscv mmio functionality.
+ */
+
+#include <linux/kvm_host.h>
+
+#include <kvm/iodev.h>
+#include "mmio_test.h"
+
+struct mmio_test {
+	struct kvm *kvm;
+	struct kvm_io_device dev;
+	unsigned long start;
+	unsigned long size;
+	char cache[16];
+};
+
+static struct mmio_test *kvm_to_mmio_test_dev(const struct kvm_io_device *dev)
+{
+	return container_of(dev, struct mmio_test, dev);
+}
+
+static int mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
+		     gpa_t addr, int len, void *val)
+{
+	struct mmio_test *mmio_test = kvm_to_mmio_test_dev(dev);
+
+	if ((addr - mmio_test->start) >= mmio_test->size)
+		return -1;
+
+	/* Write back cached value */
+	memcpy(val, &mmio_test->cache[(addr - mmio_test->start)], len);
+	return 0;
+}
+
+static int mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
+		      gpa_t addr, int len, const void *val)
+{
+	struct mmio_test *mmio_test = kvm_to_mmio_test_dev(dev);
+
+	if ((addr - mmio_test->start) >= mmio_test->size)
+		return -1;
+
+	/* Cache value */
+	memcpy(&mmio_test->cache[(addr - mmio_test->start)], val, len);
+	return 0;
+}
+
+static const struct kvm_io_device_ops mmio_ops = {
+	.read = mmio_read,
+	.write = mmio_write,
+};
+
+static int mmio_test_create(struct kvm_device *dev, u32 type)
+{
+	struct mmio_test *mmio_test;
+
+	mmio_test = kzalloc(sizeof(*mmio_test), GFP_KERNEL);
+	if (!mmio_test)
+		return -ENOMEM;
+
+	mmio_test->start = 0x20000000;
+	mmio_test->size = 0x16;
+
+	dev->private = mmio_test;
+
+	kvm_iodevice_init(&mmio_test->dev, &mmio_ops);
+	kvm_io_bus_register_dev(dev->kvm, KVM_MMIO_BUS, mmio_test->start,
+				mmio_test->size, &mmio_test->dev);
+
+	return 0;
+}
+
+static void mmio_test_release(struct kvm_device *dev)
+{
+	kfree(dev->private);
+}
+
+struct kvm_device_ops kvm_riscv_mmio_test_device_ops = {
+	.name = "kvm-riscv-mmio_test",
+	.create = mmio_test_create,
+	.release = mmio_test_release,
+};
+
+int kvm_mmio_test_ops_init(void)
+{
+	return kvm_register_device_ops(&kvm_riscv_mmio_test_device_ops,
+					KVM_DEV_TYPE_TEST);
+}
+
+void kvm_mmio_test_ops_exit(void)
+{
+	kvm_unregister_device_ops(KVM_DEV_TYPE_TEST);
+}
diff --git a/virt/kvm/mmio_test.h b/virt/kvm/mmio_test.h
new file mode 100644
index 000000000000..49a6e900eec9
--- /dev/null
+++ b/virt/kvm/mmio_test.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __KVM_MMIO_TEST_H
+#define __KVM_MMIO_TEST_H
+
+#ifdef CONFIG_KVM_MMIO_TEST
+int kvm_mmio_test_ops_init(void);
+void kvm_mmio_test_ops_exit(void);
+#else
+static inline int kvm_mmio_test_ops_init(void)
+{
+	return 0;
+}
+static inline void kvm_mmio_test_ops_exit(void)
+{
+}
+#endif
+
+#endif

-- 
2.54.0