On Tue, 2020-12-29 at 11:36 +0000, Stefan Hajnoczi wrote:
> On Tue, Dec 29, 2020 at 01:02:43PM +0300, Elena Afanasova wrote:
> > 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). Regions can be deleted by
> > setting fds to -1.
> >
> > Signed-off-by: Elena Afanasova <eafanasova@xxxxxxxxx>
> > ---
> > arch/x86/kvm/Kconfig | 1 +
> > arch/x86/kvm/Makefile | 1 +
> > arch/x86/kvm/x86.c | 1 +
> > include/linux/kvm_host.h | 17 +++
> > include/uapi/linux/kvm.h | 23 ++++
> > virt/kvm/Kconfig | 3 +
> > virt/kvm/eventfd.c | 25 +++++
> > virt/kvm/eventfd.h | 14 +++
> > virt/kvm/ioregion.c | 233
> > +++++++++++++++++++++++++++++++++++++++
> > virt/kvm/ioregion.h | 15 +++
> > virt/kvm/kvm_main.c | 20 +++-
> > 11 files changed, 350 insertions(+), 3 deletions(-)
> > 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
>
> TODO non-x86 arch support
>
> > 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..7cd667dddba9 100644
> > --- a/include/linux/kvm_host.h
> > +++ b/include/linux/kvm_host.h
> > @@ -470,6 +470,10 @@ struct kvm {
> > struct mutex resampler_lock;
> > } irqfds;
> > struct list_head ioeventfds;
> > +#endif
> > +#ifdef CONFIG_KVM_IOREGION
> > + struct list_head ioregions_mmio;
> > + struct list_head ioregions_pio;
> > #endif
> > struct kvm_vm_stat stat;
> > struct kvm_arch arch;
> > @@ -1262,6 +1266,19 @@ 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..81e775778c66 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -732,6 +732,27 @@ struct kvm_ioeventfd {
> > __u8 pad[36];
> > };
> >
> > +enum {
> > + kvm_ioregion_flag_nr_pio,
> > + kvm_ioregion_flag_nr_posted_writes,
> > + 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_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 rfd;
> > + __s32 wfd;
> > + __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 +1074,7 @@ 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 +1330,7 @@ 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..a200c3761343
> > --- /dev/null
> > +++ b/virt/kvm/ioregion.c
> > @@ -0,0 +1,233 @@
> > +// 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_mmio);
> > + INIT_LIST_HEAD(&kvm->ioregions_pio);
> > +}
> > +
> > +struct ioregion {
>
> Please add comments describing the purpose of the fields, locking,
> etc.
> For example, the list field is used with kvm->ioregions_mmio/pio.
> paddr
> is a guest physical address. size is in bytes. wf is for writing
> struct
> ioregion_cmd. rf is for reading struct ioregion_resp.
>
Ok
> > + struct list_head list;
> > + u64 paddr;
> > + u64 size;
> > + struct file *rf;
> > + struct file *wf;
> > + u64 user_data;
> > + struct kvm_io_device dev;
> > + bool posted_writes;
>
> TODO implement 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)
> > +{
> > + 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 0;
> > +}
> > +
> > +static int
> > +ioregion_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this,
> > gpa_t addr,
> > + int len, const void *val)
> > +{
> > + return 0;
> > +}
>
> The unimplemented ->read()/->write() should probably return errors.
>
You're right, it would be better
> > +
> > +/*
> > + * 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)
> > +{
> > + return (bus_idx == KVM_MMIO_BUS) ?
> > + &kvm->ioregions_mmio : &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;
> > +
> > + ioregions = get_ioregion_list(kvm, bus_idx);
> > + list_for_each_entry(_p, ioregions, list)
> > + if (overlap(start, size, _p->paddr, _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) ||
> > + kvm_eventfd_collides(kvm, bus_idx, p->paddr, 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(struct kvm *kvm, struct kvm_ioregion *args)
> > +{
> > + struct ioregion *p;
> > + bool is_posted_writes;
> > + struct file *rfile, *wfile;
> > + enum kvm_bus bus_idx;
> > + int ret = 0;
> > +
> > + if (!args->memory_size)
> > + return -EINVAL;
> > + if ((args->guest_paddr + args->memory_size - 1) < args-
> > >guest_paddr)
> > + return -EINVAL;
> > + if (args->flags & ~KVM_IOREGION_VALID_FLAG_MASK)
> > + return -EINVAL;
> > +
> > + rfile = fget(args->rfd);
> > + if (!rfile)
> > + return -EBADF;
> > + wfile = fget(args->wfd);
> > + if (!wfile) {
> > + fput(rfile);
> > + return -EBADF;
> > + }
> > + if ((rfile->f_flags & O_NONBLOCK) || (wfile->f_flags &
> > O_NONBLOCK)) {
>
> This check prevents most user errors, but the userspace process can
> still change the file descriptor flags later. Therefore the code
> needs
> to be written to fail cleanly on -EAGAIN/-EWOULDBLOCK (no infinite
> loops
> or crashes). It's worth noting this in a comment here so others
> reading
> the code are aware of this constraint.
>
Ok, I'll fix this, thanks!
> > + ret = -EINVAL;
> > + goto fail;
> > + }
> > + 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;
> > + is_posted_writes = args->flags & KVM_IOREGION_POSTED_WRITES;
> > + p->posted_writes = is_posted_writes ? true : false;
> > + bus_idx = get_bus_from_flags(args->flags);
> > +
> > + 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:
> > + fput(rfile);
> > + fput(wfile);
> > +
> > + return ret;
> > +}
> > +
> > +static int
> > +kvm_rm_ioregion(struct kvm *kvm, struct kvm_ioregion *args)
> > +{
> > + struct ioregion *p, *tmp;
> > + enum kvm_bus bus_idx;
> > + int ret = -ENOENT;
> > + struct list_head *ioregions;
> > +
> > + if (args->rfd != -1 || args->wfd != -1)
> > + return -EINVAL;
> > +
> > + bus_idx = get_bus_from_flags(args->flags);
> > + 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;
> > +}
> > +
> > +int
> > +kvm_ioregionfd(struct kvm *kvm, struct kvm_ioregion *args)
> > +{
>
> The following check can be done here to make sure the ioctl always
> returns EINVAL if unsupported flags are passed:
>
> if (args->flags & ~KVM_IOREGION_VALID_FLAG_MASK)
> return -EINVAL;
>
> (It's currently missing in kvm_rm_ioregion().)
>
Ok
> > + if (args->rfd == -1 || args->wfd == -1)
> > + 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..385d8ec6350d 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;
> >
> > @@ -4301,9 +4312,12 @@ int kvm_io_bus_register_dev(struct kvm *kvm,
> > enum kvm_bus bus_idx, gpa_t addr,
> > if (!bus)
> > return -ENOMEM;
> >
> > - /* exclude ioeventfd which is limited by maximum fd */
> > - if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
> > - return -ENOSPC;
> > + /* enforce hard limit if kmemcg is disabled and
> > + * exclude ioeventfd which is limited by maximum fd
> > + */
> > + if (!memcg_kmem_enabled())
> > + if (bus->dev_count - bus->ioeventfd_count >
> > NR_IOBUS_DEVS - 1)
> > + return -ENOSPC;
> >
> > new_bus = kmalloc(struct_size(bus, range, bus->dev_count + 1),
> > GFP_KERNEL_ACCOUNT);
>
> Please move this change to a separate patch.
Ok
