[RFC v3 1/5] KVM: add initial support for KVM_SET_IOREGION

Elena Afanasova
2021-02-21T12:12:04Z

This vm ioctl adds or removes an ioregionfd MMIO/PIO region. Guest
read and write accesses are dispatched through the given ioregionfd
instead of returning from ioctl(KVM_RUN).

Signed-off-by: Elena Afanasova <eafanasova@gmail.com>
---
v3:
- add FAST_MMIO bus support
- add KVM_IOREGION_DEASSIGN flag
- rename kvm_ioregion read/write file descriptors

arch/x86/kvm/Kconfig | 1 +
arch/x86/kvm/Makefile | 1 +
arch/x86/kvm/x86.c | 1 +
include/linux/kvm_host.h | 18 +++
include/uapi/linux/kvm.h | 25 ++++
virt/kvm/Kconfig | 3 +
virt/kvm/eventfd.c | 25 ++++
virt/kvm/eventfd.h | 14 +++
virt/kvm/ioregion.c | 265 +++++++++++++++++++++++++++++++++++++++
virt/kvm/ioregion.h | 15 +++
virt/kvm/kvm_main.c | 11 ++
11 files changed, 379 insertions(+)
create mode 100644 virt/kvm/eventfd.h
create mode 100644 virt/kvm/ioregion.c
create mode 100644 virt/kvm/ioregion.h

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index f92dfd8ef10d..b914ef375199 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -33,6 +33,7 @@ config KVM
select HAVE_KVM_IRQ_BYPASS
select HAVE_KVM_IRQ_ROUTING
select HAVE_KVM_EVENTFD
+ select KVM_IOREGION
select KVM_ASYNC_PF
select USER_RETURN_NOTIFIER
select KVM_MMIO
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index b804444e16d4..b3b17dc9f7d4 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -12,6 +12,7 @@ KVM := ../../../virt/kvm
kvm-y += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o \
$(KVM)/eventfd.o $(KVM)/irqchip.o $(KVM)/vfio.o
kvm-$(CONFIG_KVM_ASYNC_PF) += $(KVM)/async_pf.o
+kvm-$(CONFIG_KVM_IOREGION) += $(KVM)/ioregion.o

kvm-y += x86.o emulate.o i8259.o irq.o lapic.o \
i8254.o ioapic.o irq_comm.o cpuid.o pmu.o mtrr.o \
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e545a8a613b1..ddb28f5ca252 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3739,6 +3739,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_X86_USER_SPACE_MSR:
case KVM_CAP_X86_MSR_FILTER:
case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
+ case KVM_CAP_IOREGIONFD:
r = 1;
break;
case KVM_CAP_SYNC_REGS:
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 7f2e2a09ebbd..f35f0976f5cf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -470,6 +470,11 @@ struct kvm {
struct mutex resampler_lock;
} irqfds;
struct list_head ioeventfds;
+#endif
+#ifdef CONFIG_KVM_IOREGION
+ struct list_head ioregions_fast_mmio;
+ struct list_head ioregions_mmio;
+ struct list_head ioregions_pio;
#endif
struct kvm_vm_stat stat;
struct kvm_arch arch;
@@ -1262,6 +1267,19 @@ static inline int kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)

#endif /* CONFIG_HAVE_KVM_EVENTFD */

+#ifdef CONFIG_KVM_IOREGION
+void kvm_ioregionfd_init(struct kvm *kvm);
+int kvm_ioregionfd(struct kvm *kvm, struct kvm_ioregion *args);
+
+#else
+
+static inline void kvm_ioregionfd_init(struct kvm *kvm) {}
+static inline int kvm_ioregionfd(struct kvm *kvm, struct kvm_ioregion *args)
+{
+ return -ENOSYS;
+}
+#endif
+
void kvm_arch_irq_routing_update(struct kvm *kvm);

static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu)
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ca41220b40b8..a1b1a60571f8 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -732,6 +732,29 @@ struct kvm_ioeventfd {
__u8 pad[36];
};

+enum {
+ kvm_ioregion_flag_nr_pio,
+ kvm_ioregion_flag_nr_posted_writes,
+ kvm_ioregion_flag_nr_deassign,
+ kvm_ioregion_flag_nr_max,
+};
+
+#define KVM_IOREGION_PIO (1 << kvm_ioregion_flag_nr_pio)
+#define KVM_IOREGION_POSTED_WRITES (1 << kvm_ioregion_flag_nr_posted_writes)
+#define KVM_IOREGION_DEASSIGN (1 << kvm_ioregion_flag_nr_deassign)
+
+#define KVM_IOREGION_VALID_FLAG_MASK ((1 << kvm_ioregion_flag_nr_max) - 1)
+
+struct kvm_ioregion {
+ __u64 guest_paddr; /* guest physical address */
+ __u64 memory_size; /* bytes */
+ __u64 user_data;
+ __s32 read_fd;
+ __s32 write_fd;
+ __u32 flags;
+ __u8 pad[28];
+};
+
#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
@@ -1053,6 +1076,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_X86_USER_SPACE_MSR 188
#define KVM_CAP_X86_MSR_FILTER 189
#define KVM_CAP_ENFORCE_PV_FEATURE_CPUID 190
+#define KVM_CAP_IOREGIONFD 191

#ifdef KVM_CAP_IRQ_ROUTING

@@ -1308,6 +1332,7 @@ struct kvm_vfio_spapr_tce {
struct kvm_userspace_memory_region)
#define KVM_SET_TSS_ADDR _IO(KVMIO, 0x47)
#define KVM_SET_IDENTITY_MAP_ADDR _IOW(KVMIO, 0x48, __u64)
+#define KVM_SET_IOREGION _IOW(KVMIO, 0x49, struct kvm_ioregion)

/* enable ucontrol for s390 */
struct kvm_s390_ucas_mapping {
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 1c37ccd5d402..5e6620bbf000 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -17,6 +17,9 @@ config HAVE_KVM_EVENTFD
bool
select EVENTFD

+config KVM_IOREGION
+ bool
+
config KVM_MMIO
bool

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index c2323c27a28b..aadb73903f8b 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -27,6 +27,7 @@
#include <trace/events/kvm.h>

#include <kvm/iodev.h>
+#include "ioregion.h"

#ifdef CONFIG_HAVE_KVM_IRQFD

@@ -755,6 +756,23 @@ static const struct kvm_io_device_ops ioeventfd_ops = {
.destructor = ioeventfd_destructor,
};

+#ifdef CONFIG_KVM_IOREGION
+/* assumes kvm->slots_lock held */
+bool kvm_eventfd_collides(struct kvm *kvm, int bus_idx,
+ u64 start, u64 size)
+{
+ struct _ioeventfd *_p;
+
+ list_for_each_entry(_p, &kvm->ioeventfds, list)
+ if (_p->bus_idx == bus_idx &&
+ overlap(start, size, _p->addr,
+ !_p->length ? 8 : _p->length))
+ return true;
+
+ return false;
+}
+#endif
+
/* assumes kvm->slots_lock held */
static bool
ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
@@ -770,6 +788,13 @@ ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
_p->datamatch == p->datamatch))))
return true;

+#ifdef CONFIG_KVM_IOREGION
+ if (p->bus_idx == KVM_MMIO_BUS || p->bus_idx == KVM_PIO_BUS)
+ if (kvm_ioregion_collides(kvm, p->bus_idx, p->addr,
+ !p->length ? 8 : p->length))
+ return true;
+#endif
+
return false;
}

diff --git a/virt/kvm/eventfd.h b/virt/kvm/eventfd.h
new file mode 100644
index 000000000000..73a621eebae3
--- /dev/null
+++ b/virt/kvm/eventfd.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __KVM_EVENTFD_H__
+#define __KVM_EVENTFD_H__
+
+#ifdef CONFIG_KVM_IOREGION
+bool kvm_eventfd_collides(struct kvm *kvm, int bus_idx, u64 start, u64 size);
+#else
+static inline bool
+kvm_eventfd_collides(struct kvm *kvm, int bus_idx, u64 start, u64 size)
+{
+ return false;
+}
+#endif
+#endif
diff --git a/virt/kvm/ioregion.c b/virt/kvm/ioregion.c
new file mode 100644
index 000000000000..e09ef3e2c9d7
--- /dev/null
+++ b/virt/kvm/ioregion.c
@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kvm_host.h>
+#include <linux/fs.h>
+#include <kvm/iodev.h>
+#include "eventfd.h"
+
+void
+kvm_ioregionfd_init(struct kvm *kvm)
+{
+ INIT_LIST_HEAD(&kvm->ioregions_fast_mmio);
+ INIT_LIST_HEAD(&kvm->ioregions_mmio);
+ INIT_LIST_HEAD(&kvm->ioregions_pio);
+}
+
+struct ioregion {
+ struct list_head list;
+ u64 paddr; /* guest physical address */
+ u64 size; /* size in bytes */
+ struct file *rf;
+ struct file *wf;
+ u64 user_data; /* opaque token used by userspace */
+ struct kvm_io_device dev;
+ bool posted_writes;
+};
+
+static inline struct ioregion *
+to_ioregion(struct kvm_io_device *dev)
+{
+ return container_of(dev, struct ioregion, dev);
+}
+
+/* assumes kvm->slots_lock held */
+static void
+ioregion_release(struct ioregion *p)
+{
+ if (p->rf)
+ fput(p->rf);
+ fput(p->wf);
+ list_del(&p->list);
+ kfree(p);
+}
+
+static int
+ioregion_read(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
+ int len, void *val)
+{
+ return -EOPNOTSUPP;
+}
+
+static int
+ioregion_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
+ int len, const void *val)
+{
+ return -EOPNOTSUPP;
+}
+
+/*
+ * This function is called as KVM is completely shutting down. We do not
+ * need to worry about locking just nuke anything we have as quickly as possible
+ */
+static void
+ioregion_destructor(struct kvm_io_device *this)
+{
+ struct ioregion *p = to_ioregion(this);
+
+ ioregion_release(p);
+}
+
+static const struct kvm_io_device_ops ioregion_ops = {
+ .read = ioregion_read,
+ .write = ioregion_write,
+ .destructor = ioregion_destructor,
+};
+
+static inline struct list_head *
+get_ioregion_list(struct kvm *kvm, enum kvm_bus bus_idx)
+{
+ if (bus_idx == KVM_FAST_MMIO_BUS)
+ return &kvm->ioregions_fast_mmio;
+ if (bus_idx == KVM_MMIO_BUS)
+ return &kvm->ioregions_mmio;
+ if (bus_idx == KVM_PIO_BUS)
+ return &kvm->ioregions_pio;
+}
+
+/* check for not overlapping case and reverse */
+inline bool
+overlap(u64 start1, u64 size1, u64 start2, u64 size2)
+{
+ u64 end1 = start1 + size1 - 1;
+ u64 end2 = start2 + size2 - 1;
+
+ return !(end1 < start2 || start1 >= end2);
+}
+
+/* assumes kvm->slots_lock held */
+bool
+kvm_ioregion_collides(struct kvm *kvm, int bus_idx,
+ u64 start, u64 size)
+{
+ struct ioregion *p;
+ struct list_head *ioregions = get_ioregion_list(kvm, bus_idx);
+
+ list_for_each_entry(p, ioregions, list)
+ if (overlap(start, size, p->paddr, !p->size ? 8 : p->size))
+ return true;
+
+ return false;
+}
+
+/* assumes kvm->slots_lock held */
+static bool
+ioregion_collision(struct kvm *kvm, struct ioregion *p, enum kvm_bus bus_idx)
+{
+ if (kvm_ioregion_collides(kvm, bus_idx, p->paddr, !p->size ? 8 : p->size) ||
+ kvm_eventfd_collides(kvm, bus_idx, p->paddr, !p->size ? 8 : p->size))
+ return true;
+
+ return false;
+}
+
+static enum kvm_bus
+get_bus_from_flags(__u32 flags)
+{
+ if (flags & KVM_IOREGION_PIO)
+ return KVM_PIO_BUS;
+ return KVM_MMIO_BUS;
+}
+
+int
+kvm_set_ioregion_idx(struct kvm *kvm, struct kvm_ioregion *args, enum kvm_bus bus_idx)
+{
+ struct ioregion *p;
+ struct file *rfile = NULL, *wfile;
+ int ret = 0;
+
+ wfile = fget(args->write_fd);
+ if (!wfile)
+ return -EBADF;
+ if (args->memory_size) {
+ rfile = fget(args->read_fd);
+ if (!rfile) {
+ fput(wfile);
+ return -EBADF;
+ }
+ }
+ p = kzalloc(sizeof(*p), GFP_KERNEL_ACCOUNT);
+ if (!p) {
+ ret = -ENOMEM;
+ goto fail;
+ }
+
+ INIT_LIST_HEAD(&p->list);
+ p->paddr = args->guest_paddr;
+ p->size = args->memory_size;
+ p->user_data = args->user_data;
+ p->rf = rfile;
+ p->wf = wfile;
+ p->posted_writes = args->flags & KVM_IOREGION_POSTED_WRITES;
+
+ mutex_lock(&kvm->slots_lock);
+
+ if (ioregion_collision(kvm, p, bus_idx)) {
+ ret = -EEXIST;
+ goto unlock_fail;
+ }
+ kvm_iodevice_init(&p->dev, &ioregion_ops);
+ ret = kvm_io_bus_register_dev(kvm, bus_idx, p->paddr, p->size,
+ &p->dev);
+ if (ret < 0)
+ goto unlock_fail;
+ list_add_tail(&p->list, get_ioregion_list(kvm, bus_idx));
+
+ mutex_unlock(&kvm->slots_lock);
+
+ return 0;
+
+unlock_fail:
+ mutex_unlock(&kvm->slots_lock);
+ kfree(p);
+fail:
+ if (rfile)
+ fput(rfile);
+ fput(wfile);
+
+ return ret;
+}
+
+static int
+kvm_rm_ioregion_idx(struct kvm *kvm, struct kvm_ioregion *args, enum kvm_bus bus_idx)
+{
+ struct ioregion *p, *tmp;
+ int ret = -ENOENT;
+
+ struct list_head *ioregions = get_ioregion_list(kvm, bus_idx);
+
+ mutex_lock(&kvm->slots_lock);
+
+ list_for_each_entry_safe(p, tmp, ioregions, list) {
+ if (p->paddr == args->guest_paddr &&
+ p->size == args->memory_size) {
+ kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
+ ioregion_release(p);
+ ret = 0;
+ break;
+ }
+ }
+
+ mutex_unlock(&kvm->slots_lock);
+
+ return ret;
+}
+
+static int
+kvm_set_ioregion(struct kvm *kvm, struct kvm_ioregion *args)
+{
+ int ret;
+
+ enum kvm_bus bus_idx = get_bus_from_flags(args->flags);
+
+ /* check for range overflow */
+ if (args->guest_paddr + args->memory_size < args->guest_paddr)
+ return -EINVAL;
+ /* If size is ignored only posted writes are allowed */
+ if (!args->memory_size && !(args->flags & KVM_IOREGION_POSTED_WRITES))
+ return -EINVAL;
+
+ ret = kvm_set_ioregion_idx(kvm, args, bus_idx);
+ if (ret)
+ return ret;
+
+ /* If size is ignored, MMIO is also put on a FAST_MMIO bus */
+ if (!args->memory_size && bus_idx == KVM_MMIO_BUS)
+ ret = kvm_set_ioregion_idx(kvm, args, KVM_FAST_MMIO_BUS);
+ if (ret) {
+ kvm_rm_ioregion_idx(kvm, args, bus_idx);
+ return ret;
+ }
+
+ return 0;
+}
+
+static int
+kvm_rm_ioregion(struct kvm *kvm, struct kvm_ioregion *args)
+{
+ enum kvm_bus bus_idx = get_bus_from_flags(args->flags);
+ int ret = kvm_rm_ioregion_idx(kvm, args, bus_idx);
+
+ if (!args->memory_size && bus_idx == KVM_MMIO_BUS)
+ kvm_rm_ioregion_idx(kvm, args, KVM_FAST_MMIO_BUS);
+
+ return ret;
+}
+
+int
+kvm_ioregionfd(struct kvm *kvm, struct kvm_ioregion *args)
+{
+ if (args->flags & ~KVM_IOREGION_VALID_FLAG_MASK)
+ return -EINVAL;
+
+ if (args->flags & KVM_IOREGION_DEASSIGN)
+ return kvm_rm_ioregion(kvm, args);
+
+ return kvm_set_ioregion(kvm, args);
+}
diff --git a/virt/kvm/ioregion.h b/virt/kvm/ioregion.h
new file mode 100644
index 000000000000..23ffa812ec7a
--- /dev/null
+++ b/virt/kvm/ioregion.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __KVM_IOREGION_H__
+#define __KVM_IOREGION_H__
+
+#ifdef CONFIG_KVM_IOREGION
+inline bool overlap(u64 start1, u64 size1, u64 start2, u64 size2);
+bool kvm_ioregion_collides(struct kvm *kvm, int bus_idx, u64 start, u64 size);
+#else
+static inline bool
+kvm_ioregion_collides(struct kvm *kvm, int bus_idx, u64 start, u64 size)
+{
+ return false;
+}
+#endif
+#endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2541a17ff1c4..88b92fc3da51 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -747,6 +747,7 @@ static struct kvm *kvm_create_vm(unsigned long type)
mmgrab(current->mm);
kvm->mm = current->mm;
kvm_eventfd_init(kvm);
+ kvm_ioregionfd_init(kvm);
mutex_init(&kvm->lock);
mutex_init(&kvm->irq_lock);
mutex_init(&kvm->slots_lock);
@@ -3708,6 +3709,16 @@ static long kvm_vm_ioctl(struct file *filp,
r = kvm_vm_ioctl_set_memory_region(kvm, &kvm_userspace_mem);
break;
}
+ case KVM_SET_IOREGION: {
+ struct kvm_ioregion data;
+
+ r = -EFAULT;
+ if (copy_from_user(&data, argp, sizeof(data)))
+ goto out;
+
+ r = kvm_ioregionfd(kvm, &data);
+ break;
+ }
case KVM_GET_DIRTY_LOG: {
struct kvm_dirty_log log;

--
2.25.1