From: Jason Wang <jasowang@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>,
Elena Afanasova <eafanasova@gmail.com>
Cc: kvm@vger.kernel.org, jag.raman@oracle.com, elena.ufimtseva@oracle.com
Subject: Re: [RESEND RFC v2 1/4] KVM: add initial support for KVM_SET_IOREGION
Date: Thu, 18 Feb 2021 14:22:15 +0800 [thread overview]
Message-ID: <9b7c557e-08ac-bffd-256c-7e25992d213e@redhat.com> (raw)
In-Reply-To: <20210211145918.GV247031@stefanha-x1.localdomain>
On 2021/2/11 下午10:59, 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@gmail.com>
>>>> ---
>>>> 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?
>
> 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.
Yes.
>
> 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 agree.
Thanks
next prev parent reply other threads:[~2021-02-18 6:27 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-28 18:32 [RFC v2 0/4] Introduce MMIO/PIO dispatch file descriptors (ioregionfd) Elena Afanasova
2021-01-28 18:32 ` [RFC v2 2/4] KVM: x86: add support for ioregionfd signal handling Elena Afanasova
2021-01-30 16:58 ` Stefan Hajnoczi
2021-02-03 14:00 ` Elena Afanasova
2021-02-09 6:21 ` Jason Wang
2021-02-09 14:49 ` Stefan Hajnoczi
2021-02-10 19:06 ` Elena Afanasova
2021-02-09 6:26 ` Jason Wang
2021-01-28 18:32 ` [RFC v2 3/4] KVM: add support for ioregionfd cmds/replies serialization Elena Afanasova
2021-01-30 18:54 ` Stefan Hajnoczi
2021-02-03 14:10 ` Elena Afanasova
2021-01-28 18:32 ` [RFC v2 4/4] KVM: enforce NR_IOBUS_DEVS limit if kmemcg is disabled Elena Afanasova
2021-01-29 18:48 ` [RESEND RFC v2 1/4] KVM: add initial support for KVM_SET_IOREGION Elena Afanasova
2021-01-30 15:04 ` Stefan Hajnoczi
2021-02-04 13:03 ` Cornelia Huck
2021-02-05 18:39 ` Elena Afanasova
2021-02-08 11:49 ` Cornelia Huck
2021-02-08 6:21 ` Jason Wang
2021-02-09 14:59 ` Stefan Hajnoczi
2021-02-18 6:17 ` Jason Wang
2021-02-10 19:31 ` Elena Afanasova
2021-02-11 14:59 ` Stefan Hajnoczi
2021-02-17 23:05 ` Elena Afanasova
2021-02-18 6:22 ` Jason Wang [this message]
2021-02-18 6:20 ` Jason Wang
2021-01-30 14:56 ` [RFC v2 0/4] Introduce MMIO/PIO dispatch file descriptors (ioregionfd) Stefan Hajnoczi
2021-02-02 14:59 ` Stefan Hajnoczi
2021-02-08 6:02 ` Jason Wang
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