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[37.145.186.126]) by smtp.gmail.com with ESMTPSA id e20sm8412214ljn.8.2021.01.03.12.33.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 03 Jan 2021 12:33:07 -0800 (PST) Message-ID: <0cc68c81d6fae042d8a84bf90dd77eecd4da7cc8.camel@gmail.com> Subject: Re: [RFC 1/2] KVM: add initial support for KVM_SET_IOREGION From: Elena Afanasova To: Jason Wang , kvm@vger.kernel.org Cc: stefanha@redhat.com, jag.raman@oracle.com, elena.ufimtseva@oracle.com Date: Sun, 03 Jan 2021 12:32:53 -0800 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.4-0ubuntu1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 2020-12-31 at 11:45 +0800, Jason Wang wrote: > On 2020/12/29 下午6:02, Elena Afanasova wrote: > > This vm ioctl adds or removes an ioregionfd MMIO/PIO region. > > How about FAST_MMIO? > I’ll add KVM_IOREGION_FAST_MMIO flag support. So this may be suitable for triggers which could use posted writes. The struct ioregionfd_cmd size bits and the data field will be unused in this case. > > > 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 > > --- > > 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 > > 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; > > What will this field do? Is it a token? > Yes, it’s an opaque token that can be used by userspace in order to determine which MemoryRegion to dispatch. > > > + __s32 rfd; > > + __s32 wfd; > > + __u32 flags; > > + __u8 pad[28]; > > +}; > > Is this possible to register the same fd with multiple GPA ranges? > If > not, do we need to check for fd collision? > Yes, it’s possible to register the same fd with multiple GPA ranges. > > > + > > #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 > > > > #include > > +#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 > > +#include > > +#include > > +#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; > > + u64 size; > > + struct file *rf; > > + struct file *wf; > > + u64 user_data; > > + 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 0; > > +} > > + > > +static int > > +ioregion_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, > > gpa_t addr, > > + int len, const void *val) > > +{ > > + return 0; > > +} > > + > > +/* > > + * 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)) { > > + ret = -EINVAL; > > + goto fail; > > + } > > Instead of checking nonblocking, can we poll here? > Yes, it’s possible. It would be necessary in the case of out-of-order requests. But since multiple in-flight messages don’t seem to be a use case I’m not sure if it’s necessary. Typically device register accesses should not take a long time, so making them asynchronous doesn't seem like a practical advantage. Also this might complicate the code and make it slower. What do you think? > > > + 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; > > We probably need to register to FAST_MMIO when bus_idx is MMIO. > > > > + 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; > > If we want to use ioregion fd for doorbell, rfd is probably not > necessary here. > This condition is simply a requirement that region can be deleted in the case of both fds are set to -1. > Thanks > > > > + > > + 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) > > +{ > > + 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);