On Thu, 2021-02-11 at 14:59 +0000, Stefan Hajnoczi wrote:
> On Wed, Feb 10, 2021 at 11:31:30AM -0800, Elena Afanasova wrote:
> > On Mon, 2021-02-08 at 14:21 +0800, Jason Wang wrote:
> > > On 2021/1/30 上午2:48, 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>
> > > > ---
> > > > Changes in v2:
> > > > - changes after code review
> > > >
> > > > 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 | 232
> > > > +++++++++++++++++++++++++++++++++++++++
> > > > virt/kvm/ioregion.h | 15 +++
> > > > virt/kvm/kvm_main.c | 11 ++
> > > > 11 files changed, 343 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..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 */
> > >
> > > Do we really need __u64 here?
> > >
> > >
> > > > + __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..48ff92bca966
> > > > --- /dev/null
> > > > +++ b/virt/kvm/ioregion.c
> > > > @@ -0,0 +1,232 @@
> > > > +// 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 {
> > > > + 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)
> > > > +{
> > > > + 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)
> > > > +{
> > > > + 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;
> > > > + 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;
> > > > +
> > > > + rfile = fget(args->rfd);
> > > > + if (!rfile)
> > > > + return -EBADF;
> > >
> > > So the question still, if we want to use ioregion fd for
> > > doorbell,
> > > we
> > > don't need rfd in this case?
> > >
> > Using ioregionfd for doorbell seems to be an open question.
> > Probably it
> > could just focus on the non-doorbell cases.
>
> Below you replied FAST_MMIO will be in v3. That is the doorbell case,
> so
> maybe it is in scope for this patch series?
>
Ok, will fix
> I think continuing to use ioeventfd for most doorbell registers makes
> sense.
>
> However, there are two cases where ioregionfd doorbell support is
> interesting:
>
> 1. The (non-FAST_MMIO) case where the application needs to know the
> value written to the doorbell. ioeventfd cannot do this (datamatch
> can handle a subset of cases but not all) so we need ioregionfd
> for
> this.
>
> 2. The FAST_MMIO case just for convenience if applications prefer to
> use
> a single API (ioregionfd) instead of implementing both ioregionfd
> and
> ioeventfd.
>
> ioeventfd will still have its benefits (and limitations) that make it
> different from ioregionfd. In particular, ioregionfd will not merge
> doorbell writes into a single message because doing so would
> basically
> involve reimplementing ioeventfd functionality as part of ioregionfd
> and
> isn't compatible with the current approach where userspace can
> provide
> any file descriptor for communication.
>
> Elena and Jason: do you agree with this API design?
I’m still not sure about coalescing the writes support, but in general
it looks ok to me.
