Re: [PATCH kernel v8 10/10] KVM: PPC: VFIO: Add in-kernel acceleration for VFIO

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On Tue, Mar 14, 2017 at 03:05:27PM -0600, Alex Williamson wrote:
> On Fri, 10 Mar 2017 14:53:37 +1100
> Alexey Kardashevskiy <aik@xxxxxxxxx> wrote:
> 
> > This allows the host kernel to handle H_PUT_TCE, H_PUT_TCE_INDIRECT
> > and H_STUFF_TCE requests targeted an IOMMU TCE table used for VFIO
> > without passing them to user space which saves time on switching
> > to user space and back.
> > 
> > This adds H_PUT_TCE/H_PUT_TCE_INDIRECT/H_STUFF_TCE handlers to KVM.
> > KVM tries to handle a TCE request in the real mode, if failed
> > it passes the request to the virtual mode to complete the operation.
> > If it a virtual mode handler fails, the request is passed to
> > the user space; this is not expected to happen though.
> > 
> > To avoid dealing with page use counters (which is tricky in real mode),
> > this only accelerates SPAPR TCE IOMMU v2 clients which are required
> > to pre-register the userspace memory. The very first TCE request will
> > be handled in the VFIO SPAPR TCE driver anyway as the userspace view
> > of the TCE table (iommu_table::it_userspace) is not allocated till
> > the very first mapping happens and we cannot call vmalloc in real mode.
> > 
> > If we fail to update a hardware IOMMU table unexpected reason, we just
> > clear it and move on as there is nothing really we can do about it -
> > for example, if we hot plug a VFIO device to a guest, existing TCE tables
> > will be mirrored automatically to the hardware and there is no interface
> > to report to the guest about possible failures.
> > 
> > This adds new attribute - KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE - to
> > the VFIO KVM device. It takes a VFIO group fd and SPAPR TCE table fd
> > and associates a physical IOMMU table with the SPAPR TCE table (which
> > is a guest view of the hardware IOMMU table). The iommu_table object
> > is cached and referenced so we do not have to look up for it in real mode.
> > 
> > This does not implement the UNSET counterpart as there is no use for it -
> > once the acceleration is enabled, the existing userspace won't
> > disable it unless a VFIO container is destroyed; this adds necessary
> > cleanup to the KVM_DEV_VFIO_GROUP_DEL handler.
> > 
> > As this creates a descriptor per IOMMU table-LIOBN couple (called
> > kvmppc_spapr_tce_iommu_table), it is possible to have several
> > descriptors with the same iommu_table (hardware IOMMU table) attached
> > to the same LIOBN; we do not remove duplicates though as
> > iommu_table_ops::exchange not just update a TCE entry (which is
> > shared among IOMMU groups) but also invalidates the TCE cache
> > (one per IOMMU group).
> > 
> > This advertises the new KVM_CAP_SPAPR_TCE_VFIO capability to the user
> > space.
> > 
> > This adds real mode version of WARN_ON_ONCE() as the generic version
> > causes problems with rcu_sched. Since we testing what vmalloc_to_phys()
> > returns in the code, this also adds a check for already existing
> > vmalloc_to_phys() call in kvmppc_rm_h_put_tce_indirect().
> > 
> > This finally makes use of vfio_external_user_iommu_id() which was
> > introduced quite some time ago and was considered for removal.
> > 
> > Tests show that this patch increases transmission speed from 220MB/s
> > to 750..1020MB/s on 10Gb network (Chelsea CXGB3 10Gb ethernet card).
> > 
> > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
> > ---
> > Changes:
> > v8:
> > * changed all (!pua) checks to return H_TOO_HARD as ioctl() is supposed
> > to handle them
> > * changed vmalloc_to_phys() callers to return H_HARDWARE
> > * changed real mode iommu_tce_xchg_rm() callers to return H_TOO_HARD
> > and added a comment about this in the code
> > * changed virtual mode iommu_tce_xchg() callers to return H_HARDWARE
> > and do WARN_ON
> > * added WARN_ON_ONCE_RM(!rmap) in kvmppc_rm_h_put_tce_indirect() to
> > have all vmalloc_to_phys() callsites covered
> > 
> > v7:
> > * added realmode-friendly WARN_ON_ONCE_RM
> > 
> > v6:
> > * changed handling of errors returned by kvmppc_(rm_)tce_iommu_(un)map()
> > * moved kvmppc_gpa_to_ua() to TCE validation
> > 
> > v5:
> > * changed error codes in multiple places
> > * added bunch of WARN_ON() in places which should not really happen
> > * adde a check that an iommu table is not attached already to LIOBN
> > * dropped explicit calls to iommu_tce_clear_param_check/
> > iommu_tce_put_param_check as kvmppc_tce_validate/kvmppc_ioba_validate
> > call them anyway (since the previous patch)
> > * if we fail to update a hardware IOMMU table for unexpected reason,
> > this just clears the entry
> > 
> > v4:
> > * added note to the commit log about allowing multiple updates of
> > the same IOMMU table;
> > * instead of checking for if any memory was preregistered, this
> > returns H_TOO_HARD if a specific page was not;
> > * fixed comments from v3 about error handling in many places;
> > * simplified TCE handlers and merged IOMMU parts inline - for example,
> > there used to be kvmppc_h_put_tce_iommu(), now it is merged into
> > kvmppc_h_put_tce(); this allows to check IOBA boundaries against
> > the first attached table only (makes the code simpler);
> > 
> > v3:
> > * simplified not to use VFIO group notifiers
> > * reworked cleanup, should be cleaner/simpler now
> > 
> > v2:
> > * reworked to use new VFIO notifiers
> > * now same iommu_table may appear in the list several times, to be fixed later
> > ---
> >  Documentation/virtual/kvm/devices/vfio.txt |  22 +-
> >  arch/powerpc/include/asm/kvm_host.h        |   8 +
> >  arch/powerpc/include/asm/kvm_ppc.h         |   4 +
> >  include/uapi/linux/kvm.h                   |   8 +
> >  arch/powerpc/kvm/book3s_64_vio.c           | 323 ++++++++++++++++++++++++++++-
> >  arch/powerpc/kvm/book3s_64_vio_hv.c        | 201 +++++++++++++++++-
> >  arch/powerpc/kvm/powerpc.c                 |   2 +
> >  virt/kvm/vfio.c                            |  60 ++++++
> >  8 files changed, 623 insertions(+), 5 deletions(-)
> > 
> > diff --git a/Documentation/virtual/kvm/devices/vfio.txt b/Documentation/virtual/kvm/devices/vfio.txt
> > index ef51740c67ca..f95d867168ea 100644
> > --- a/Documentation/virtual/kvm/devices/vfio.txt
> > +++ b/Documentation/virtual/kvm/devices/vfio.txt
> > @@ -16,7 +16,25 @@ Groups:
> >  
> >  KVM_DEV_VFIO_GROUP attributes:
> >    KVM_DEV_VFIO_GROUP_ADD: Add a VFIO group to VFIO-KVM device tracking
> > +	kvm_device_attr.addr points to an int32_t file descriptor
> > +	for the VFIO group.
> >    KVM_DEV_VFIO_GROUP_DEL: Remove a VFIO group from VFIO-KVM device tracking
> > +	kvm_device_attr.addr points to an int32_t file descriptor
> > +	for the VFIO group.
> > +  KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
> > +	allocated by sPAPR KVM.
> > +	kvm_device_attr.addr points to a struct:
> >  
> > -For each, kvm_device_attr.addr points to an int32_t file descriptor
> > -for the VFIO group.
> > +	struct kvm_vfio_spapr_tce {
> > +		__u32	argsz;
> > +		__u32	flags;
> > +		__s32	groupfd;
> > +		__s32	tablefd;
> > +	};
> > +
> > +	where
> > +	@argsz is the size of kvm_vfio_spapr_tce_liobn;
> 
> kvm_vfio_spapr_tce_liobn does not exist.  s/_liobn//?
> 
> > +	@flags are not supported now, must be zero;
> 
> We do this argsz/flags thing on vfio ioctls because ioctls are a bit
> more of a restricted resource.  We don't want to burn through them so
> we make them expandable.  I don't know that we have that restriction
> here and the ADD/DEL support certainly doesn't include it.  Maybe this
> isn't necessary?

I didn't comment on this before, but I tend to agree with Alex here.

> > +	@groupfd is a file descriptor for a VFIO group;
> > +	@tablefd is a file descriptor for a TCE table allocated via
> > +		KVM_CREATE_SPAPR_TCE.
> > diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> > index 7bba8f415627..857ae2c6aa39 100644
> > --- a/arch/powerpc/include/asm/kvm_host.h
> > +++ b/arch/powerpc/include/asm/kvm_host.h
> > @@ -191,6 +191,13 @@ struct kvmppc_pginfo {
> >  	atomic_t refcnt;
> >  };
> >  
> > +struct kvmppc_spapr_tce_iommu_table {
> > +	struct rcu_head rcu;
> > +	struct list_head next;
> > +	struct vfio_group *group;
> > +	struct iommu_table *tbl;
> > +};
> > +
> >  struct kvmppc_spapr_tce_table {
> >  	struct list_head list;
> >  	struct kvm *kvm;
> > @@ -199,6 +206,7 @@ struct kvmppc_spapr_tce_table {
> >  	u32 page_shift;
> >  	u64 offset;		/* in pages */
> >  	u64 size;		/* window size in pages */
> > +	struct list_head iommu_tables;
> >  	struct page *pages[0];
> >  };
> >  
> > diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> > index 72c2a155641f..66de7e73b3d3 100644
> > --- a/arch/powerpc/include/asm/kvm_ppc.h
> > +++ b/arch/powerpc/include/asm/kvm_ppc.h
> > @@ -164,6 +164,10 @@ extern long kvmppc_prepare_vrma(struct kvm *kvm,
> >  extern void kvmppc_map_vrma(struct kvm_vcpu *vcpu,
> >  			struct kvm_memory_slot *memslot, unsigned long porder);
> >  extern int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu);
> > +extern long kvm_spapr_tce_attach_iommu_group(struct kvm *kvm, int tablefd,
> > +		struct vfio_group *group);
> > +extern void kvm_spapr_tce_release_iommu_group(struct kvm *kvm,
> > +		struct vfio_group *group);
> >  
> >  extern long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> >  				struct kvm_create_spapr_tce_64 *args);
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index f5a52ffb6b58..e743cb0d176e 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -1088,6 +1088,7 @@ struct kvm_device_attr {
> >  #define  KVM_DEV_VFIO_GROUP			1
> >  #define   KVM_DEV_VFIO_GROUP_ADD			1
> >  #define   KVM_DEV_VFIO_GROUP_DEL			2
> > +#define   KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE		3
> >  
> >  enum kvm_device_type {
> >  	KVM_DEV_TYPE_FSL_MPIC_20	= 1,
> > @@ -1109,6 +1110,13 @@ enum kvm_device_type {
> >  	KVM_DEV_TYPE_MAX,
> >  };
> >  
> > +struct kvm_vfio_spapr_tce {
> > +	__u32	argsz;
> > +	__u32	flags;
> > +	__s32	groupfd;
> > +	__s32	tablefd;
> > +};
> > +
> >  /*
> >   * ioctls for VM fds
> >   */
> > diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
> > index e96a4590464c..be18cda01e1b 100644
> > --- a/arch/powerpc/kvm/book3s_64_vio.c
> > +++ b/arch/powerpc/kvm/book3s_64_vio.c
> > @@ -28,6 +28,10 @@
> >  #include <linux/hugetlb.h>
> >  #include <linux/list.h>
> >  #include <linux/anon_inodes.h>
> > +#include <linux/iommu.h>
> > +#include <linux/file.h>
> > +#include <linux/vfio.h>
> > +#include <linux/module.h>
> >  
> >  #include <asm/tlbflush.h>
> >  #include <asm/kvm_ppc.h>
> > @@ -40,6 +44,36 @@
> >  #include <asm/udbg.h>
> >  #include <asm/iommu.h>
> >  #include <asm/tce.h>
> > +#include <asm/mmu_context.h>
> > +
> > +static void kvm_vfio_group_put_external_user(struct vfio_group *vfio_group)
> > +{
> > +	void (*fn)(struct vfio_group *);
> > +
> > +	fn = symbol_get(vfio_group_put_external_user);
> > +	if (WARN_ON(!fn))
> > +		return;
> > +
> > +	fn(vfio_group);
> > +
> > +	symbol_put(vfio_group_put_external_user);
> > +}
> > +
> > +static int kvm_vfio_external_user_iommu_id(struct vfio_group *vfio_group)
> > +{
> > +	int (*fn)(struct vfio_group *);
> > +	int ret = -1;
> > +
> > +	fn = symbol_get(vfio_external_user_iommu_id);
> > +	if (!fn)
> > +		return ret;
> > +
> > +	ret = fn(vfio_group);
> > +
> > +	symbol_put(vfio_external_user_iommu_id);
> > +
> > +	return ret;
> > +}
> 
> 
> Ugh.  This feels so wrong.  Why can't you have kvm-vfio pass the
> iommu_group?  Why do you need to hold this additional vfio_group
> reference?

Keeping the vfio_group reference makes sense to me, since we don't
want the vfio context for the group to go away while it's attached to
the LIOBN.

However, going via the iommu_id rather than just having an interface
to directly grab the iommu group from the vfio_group seems bizarre to
me.  I'm ok with cleaning that up later, however.

> 
> >  
> >  static unsigned long kvmppc_tce_pages(unsigned long iommu_pages)
> >  {
> > @@ -91,6 +125,130 @@ static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
> >  	return ret;
> >  }
> >  
> > +static void kvm_spapr_tce_iommu_table_free(struct rcu_head *head)
> > +{
> > +	struct kvmppc_spapr_tce_iommu_table *stit = container_of(head,
> > +			struct kvmppc_spapr_tce_iommu_table, rcu);
> > +
> > +	iommu_table_put(stit->tbl);
> > +	kvm_vfio_group_put_external_user(stit->group);
> > +
> > +	kfree(stit);
> > +}
> > +
> > +static void kvm_spapr_tce_liobn_release_iommu_group(
> > +		struct kvmppc_spapr_tce_table *stt,
> > +		struct vfio_group *group)
> > +{
> > +	struct kvmppc_spapr_tce_iommu_table *stit, *tmp;
> > +
> > +	list_for_each_entry_safe(stit, tmp, &stt->iommu_tables, next) {
> > +		if (group && (stit->group != group))
> > +			continue;
> > +
> > +		list_del_rcu(&stit->next);
> > +
> > +		call_rcu(&stit->rcu, kvm_spapr_tce_iommu_table_free);
> > +	}
> > +}
> > +
> > +extern void kvm_spapr_tce_release_iommu_group(struct kvm *kvm,
> > +		struct vfio_group *group)
> > +{
> > +	struct kvmppc_spapr_tce_table *stt;
> > +
> > +	list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list)
> > +		kvm_spapr_tce_liobn_release_iommu_group(stt, group);
> > +}
> > +
> > +extern long kvm_spapr_tce_attach_iommu_group(struct kvm *kvm, int tablefd,
> > +		struct vfio_group *group)
> > +{
> > +	struct kvmppc_spapr_tce_table *stt = NULL;
> > +	bool found = false;
> > +	struct iommu_table *tbl = NULL;
> > +	struct iommu_table_group *table_group;
> > +	long i, ret = 0;
> > +	struct kvmppc_spapr_tce_iommu_table *stit;
> > +	struct fd f;
> > +	int group_id;
> > +	struct iommu_group *grp;
> > +
> > +	group_id = kvm_vfio_external_user_iommu_id(group);
> > +	grp = iommu_group_get_by_id(group_id);
> > +	if (WARN_ON(!grp))
> > +		return -EIO;
> > +
> > +	f = fdget(tablefd);
> > +	if (!f.file) {
> > +		ret = -EBADF;
> > +		goto put_exit;
> > +	}
> > +
> > +	list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list) {
> > +		if (stt == f.file->private_data) {
> > +			found = true;
> > +			break;
> > +		}
> > +	}
> > +
> > +	fdput(f);
> > +
> > +	if (!found) {
> > +		ret = -EINVAL;
> > +		goto put_exit;
> > +	}
> > +
> > +	table_group = iommu_group_get_iommudata(grp);
> > +	if (WARN_ON(!table_group)) {
> > +		ret = -EFAULT;
> > +		goto put_exit;
> > +	}
> > +
> > +	for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
> > +		struct iommu_table *tbltmp = table_group->tables[i];
> > +
> > +		if (!tbltmp)
> > +			continue;
> > +
> > +		/*
> > +		 * Make sure hardware table parameters are exactly the same;
> > +		 * this is used in the TCE handlers where boundary checks
> > +		 * use only the first attached table.
> > +		 */
> > +		if ((tbltmp->it_page_shift == stt->page_shift) &&
> > +				(tbltmp->it_offset == stt->offset) &&
> > +				(tbltmp->it_size == stt->size)) {
> > +			tbl = tbltmp;
> > +			break;
> > +		}
> > +	}
> > +	if (!tbl) {
> > +		ret = -EINVAL;
> > +		goto put_exit;
> > +	}
> > +
> > +	list_for_each_entry_rcu(stit, &stt->iommu_tables, next) {
> > +		if ((stit->tbl == tbl) && (stit->group == group)) {
> > +			ret = -EBUSY;
> > +			goto put_exit;
> > +		}
> > +	}
> > +
> > +	iommu_table_get(tbl);
> > +
> > +	stit = kzalloc(sizeof(*stit), GFP_KERNEL);
> > +	stit->tbl = tbl;
> > +	stit->group = group;
> > +
> > +	list_add_rcu(&stit->next, &stt->iommu_tables);
> > +
> > +put_exit:
> > +	iommu_group_put(grp);
> > +
> > +	return ret;
> > +}
> > +
> >  static void release_spapr_tce_table(struct rcu_head *head)
> >  {
> >  	struct kvmppc_spapr_tce_table *stt = container_of(head,
> > @@ -133,6 +291,8 @@ static int kvm_spapr_tce_release(struct inode *inode, struct file *filp)
> >  
> >  	list_del_rcu(&stt->list);
> >  
> > +	kvm_spapr_tce_liobn_release_iommu_group(stt, NULL /* release all */);
> > +
> >  	kvm_put_kvm(stt->kvm);
> >  
> >  	kvmppc_account_memlimit(
> > @@ -183,6 +343,7 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> >  	stt->offset = args->offset;
> >  	stt->size = size;
> >  	stt->kvm = kvm;
> > +	INIT_LIST_HEAD_RCU(&stt->iommu_tables);
> >  
> >  	for (i = 0; i < npages; i++) {
> >  		stt->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
> > @@ -211,11 +372,101 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> >  	return ret;
> >  }
> >  
> > +static void kvmppc_clear_tce(struct iommu_table *tbl, unsigned long entry)
> > +{
> > +	unsigned long hpa = 0;
> > +	enum dma_data_direction dir = DMA_NONE;
> > +
> > +	iommu_tce_xchg(tbl, entry, &hpa, &dir);
> > +}
> > +
> > +static long kvmppc_tce_iommu_mapped_dec(struct kvm *kvm,
> > +		struct iommu_table *tbl, unsigned long entry)
> > +{
> > +	struct mm_iommu_table_group_mem_t *mem = NULL;
> > +	const unsigned long pgsize = 1ULL << tbl->it_page_shift;
> > +	unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> > +
> > +	if (!pua)
> > +		/* it_userspace allocation might be delayed */
> > +		return H_TOO_HARD;
> > +
> > +	mem = mm_iommu_lookup(kvm->mm, *pua, pgsize);
> > +	if (!mem)
> > +		return H_TOO_HARD;
> > +
> > +	mm_iommu_mapped_dec(mem);
> > +
> > +	*pua = 0;
> > +
> > +	return H_SUCCESS;
> > +}
> > +
> > +static long kvmppc_tce_iommu_unmap(struct kvm *kvm,
> > +		struct iommu_table *tbl, unsigned long entry)
> > +{
> > +	enum dma_data_direction dir = DMA_NONE;
> > +	unsigned long hpa = 0;
> > +	long ret;
> > +
> > +	if (WARN_ON_ONCE(iommu_tce_xchg(tbl, entry, &hpa, &dir)))
> > +		return H_HARDWARE;
> > +
> > +	if (dir == DMA_NONE)
> > +		return H_SUCCESS;
> > +
> > +	ret = kvmppc_tce_iommu_mapped_dec(kvm, tbl, entry);
> > +	if (ret != H_SUCCESS)
> > +		iommu_tce_xchg(tbl, entry, &hpa, &dir);
> > +
> > +	return ret;
> > +}
> > +
> > +long kvmppc_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
> > +		unsigned long entry, unsigned long ua,
> > +		enum dma_data_direction dir)
> > +{
> > +	long ret;
> > +	unsigned long hpa, *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> > +	struct mm_iommu_table_group_mem_t *mem;
> > +
> > +	if (!pua)
> > +		/* it_userspace allocation might be delayed */
> > +		return H_TOO_HARD;
> > +
> > +	mem = mm_iommu_lookup(kvm->mm, ua, 1ULL << tbl->it_page_shift);
> > +	if (!mem)
> > +		/* This only handles v2 IOMMU type, v1 is handled via ioctl() */
> > +		return H_TOO_HARD;
> > +
> > +	if (WARN_ON_ONCE(mm_iommu_ua_to_hpa(mem, ua, &hpa)))
> > +		return H_HARDWARE;
> > +
> > +	if (mm_iommu_mapped_inc(mem))
> > +		return H_CLOSED;
> > +
> > +	ret = iommu_tce_xchg(tbl, entry, &hpa, &dir);
> > +	if (WARN_ON_ONCE(ret)) {
> > +		mm_iommu_mapped_dec(mem);
> > +		return H_HARDWARE;
> > +	}
> > +
> > +	if (dir != DMA_NONE)
> > +		kvmppc_tce_iommu_mapped_dec(kvm, tbl, entry);
> > +
> > +	*pua = ua;
> > +
> > +	return 0;
> > +}
> > +
> >  long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> >  		      unsigned long ioba, unsigned long tce)
> >  {
> >  	struct kvmppc_spapr_tce_table *stt;
> > -	long ret;
> > +	long ret, idx;
> > +	struct kvmppc_spapr_tce_iommu_table *stit;
> > +	unsigned long entry, ua = 0;
> > +	enum dma_data_direction dir;
> >  
> >  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
> >  	/* 	    liobn, ioba, tce); */
> > @@ -232,7 +483,35 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> >  	if (ret != H_SUCCESS)
> >  		return ret;
> >  
> > -	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
> > +	dir = iommu_tce_direction(tce);
> > +	if ((dir != DMA_NONE) && kvmppc_gpa_to_ua(vcpu->kvm,
> > +			tce & ~(TCE_PCI_READ | TCE_PCI_WRITE), &ua, NULL))
> > +		return H_PARAMETER;
> > +
> > +	entry = ioba >> stt->page_shift;
> > +
> > +	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> > +		if (dir == DMA_NONE) {
> > +			ret = kvmppc_tce_iommu_unmap(vcpu->kvm,
> > +					stit->tbl, entry);
> > +		} else {
> > +			idx = srcu_read_lock(&vcpu->kvm->srcu);
> > +			ret = kvmppc_tce_iommu_map(vcpu->kvm, stit->tbl,
> > +					entry, ua, dir);
> > +			srcu_read_unlock(&vcpu->kvm->srcu, idx);
> > +		}
> > +
> > +		if (ret == H_SUCCESS)
> > +			continue;
> > +
> > +		if (ret == H_TOO_HARD)
> > +			return ret;
> > +
> > +		WARN_ON_ONCE(1);
> > +		kvmppc_clear_tce(stit->tbl, entry);
> > +	}
> > +
> > +	kvmppc_tce_put(stt, entry, tce);
> >  
> >  	return H_SUCCESS;
> >  }
> > @@ -247,6 +526,7 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >  	unsigned long entry, ua = 0;
> >  	u64 __user *tces;
> >  	u64 tce;
> > +	struct kvmppc_spapr_tce_iommu_table *stit;
> >  
> >  	stt = kvmppc_find_table(vcpu->kvm, liobn);
> >  	if (!stt)
> > @@ -285,6 +565,26 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >  		if (ret != H_SUCCESS)
> >  			goto unlock_exit;
> >  
> > +		if (kvmppc_gpa_to_ua(vcpu->kvm,
> > +				tce & ~(TCE_PCI_READ | TCE_PCI_WRITE),
> > +				&ua, NULL))
> > +			return H_PARAMETER;
> > +
> > +		list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> > +			ret = kvmppc_tce_iommu_map(vcpu->kvm,
> > +					stit->tbl, entry + i, ua,
> > +					iommu_tce_direction(tce));
> > +
> > +			if (ret == H_SUCCESS)
> > +				continue;
> > +
> > +			if (ret == H_TOO_HARD)
> > +				goto unlock_exit;
> > +
> > +			WARN_ON_ONCE(1);
> > +			kvmppc_clear_tce(stit->tbl, entry);
> > +		}
> > +
> >  		kvmppc_tce_put(stt, entry + i, tce);
> >  	}
> >  
> > @@ -301,6 +601,7 @@ long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
> >  {
> >  	struct kvmppc_spapr_tce_table *stt;
> >  	long i, ret;
> > +	struct kvmppc_spapr_tce_iommu_table *stit;
> >  
> >  	stt = kvmppc_find_table(vcpu->kvm, liobn);
> >  	if (!stt)
> > @@ -314,6 +615,24 @@ long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
> >  	if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
> >  		return H_PARAMETER;
> >  
> > +	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> > +		unsigned long entry = ioba >> stit->tbl->it_page_shift;
> > +
> > +		for (i = 0; i < npages; ++i) {
> > +			ret = kvmppc_tce_iommu_unmap(vcpu->kvm,
> > +					stit->tbl, entry + i);
> > +
> > +			if (ret == H_SUCCESS)
> > +				continue;
> > +
> > +			if (ret == H_TOO_HARD)
> > +				return ret;
> > +
> > +			WARN_ON_ONCE(1);
> > +			kvmppc_clear_tce(stit->tbl, entry);
> > +		}
> > +	}
> > +
> >  	for (i = 0; i < npages; ++i, ioba += (1ULL << stt->page_shift))
> >  		kvmppc_tce_put(stt, ioba >> stt->page_shift, tce_value);
> >  
> > diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
> > index 440d3ab5dc32..eda0a8f6fae8 100644
> > --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
> > +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
> > @@ -40,6 +40,31 @@
> >  #include <asm/iommu.h>
> >  #include <asm/tce.h>
> >  
> > +#ifdef CONFIG_BUG
> > +
> > +#define WARN_ON_ONCE_RM(condition)	({			\
> > +	static bool __section(.data.unlikely) __warned;		\
> > +	int __ret_warn_once = !!(condition);			\
> > +								\
> > +	if (unlikely(__ret_warn_once && !__warned)) {		\
> > +		__warned = true;				\
> > +		pr_err("WARN_ON_ONCE_RM: (%s) at %s:%u\n",	\
> > +				__stringify(condition),		\
> > +				__func__, __LINE__);		\
> > +		dump_stack();					\
> > +	}							\
> > +	unlikely(__ret_warn_once);				\
> > +})
> > +
> > +#else
> > +
> > +#define WARN_ON_ONCE_RM(condition) ({				\
> > +	int __ret_warn_on = !!(condition);			\
> > +	unlikely(__ret_warn_on);				\
> > +})
> > +
> > +#endif
> > +
> >  #define TCES_PER_PAGE	(PAGE_SIZE / sizeof(u64))
> >  
> >  /*
> > @@ -161,11 +186,117 @@ long kvmppc_gpa_to_ua(struct kvm *kvm, unsigned long gpa,
> >  EXPORT_SYMBOL_GPL(kvmppc_gpa_to_ua);
> >  
> >  #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
> > +static void kvmppc_rm_clear_tce(struct iommu_table *tbl, unsigned long entry)
> > +{
> > +	unsigned long hpa = 0;
> > +	enum dma_data_direction dir = DMA_NONE;
> > +
> > +	iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
> > +}
> > +
> > +static long kvmppc_rm_tce_iommu_mapped_dec(struct kvm *kvm,
> > +		struct iommu_table *tbl, unsigned long entry)
> > +{
> > +	struct mm_iommu_table_group_mem_t *mem = NULL;
> > +	const unsigned long pgsize = 1ULL << tbl->it_page_shift;
> > +	unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> > +
> > +	if (!pua)
> > +		/* it_userspace allocation might be delayed */
> > +		return H_TOO_HARD;
> > +
> > +	pua = (void *) vmalloc_to_phys(pua);
> > +	if (WARN_ON_ONCE_RM(!pua))
> > +		return H_HARDWARE;
> > +
> > +	mem = mm_iommu_lookup_rm(kvm->mm, *pua, pgsize);
> > +	if (!mem)
> > +		return H_TOO_HARD;
> > +
> > +	mm_iommu_mapped_dec(mem);
> > +
> > +	*pua = 0;
> > +
> > +	return H_SUCCESS;
> > +}
> > +
> > +static long kvmppc_rm_tce_iommu_unmap(struct kvm *kvm,
> > +		struct iommu_table *tbl, unsigned long entry)
> > +{
> > +	enum dma_data_direction dir = DMA_NONE;
> > +	unsigned long hpa = 0;
> > +	long ret;
> > +
> > +	if (iommu_tce_xchg_rm(tbl, entry, &hpa, &dir))
> > +		/*
> > +		 * real mode xchg can fail if struct page crosses
> > +		 * a page boundary
> > +		 */
> > +		return H_TOO_HARD;
> > +
> > +	if (dir == DMA_NONE)
> > +		return H_SUCCESS;
> > +
> > +	ret = kvmppc_rm_tce_iommu_mapped_dec(kvm, tbl, entry);
> > +	if (ret)
> > +		iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
> > +
> > +	return ret;
> > +}
> > +
> > +static long kvmppc_rm_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
> > +		unsigned long entry, unsigned long ua,
> > +		enum dma_data_direction dir)
> > +{
> > +	long ret;
> > +	unsigned long hpa = 0;
> > +	unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
> > +	struct mm_iommu_table_group_mem_t *mem;
> > +
> > +	if (!pua)
> > +		/* it_userspace allocation might be delayed */
> > +		return H_TOO_HARD;
> > +
> > +	mem = mm_iommu_lookup_rm(kvm->mm, ua, 1ULL << tbl->it_page_shift);
> > +	if (!mem)
> > +		return H_TOO_HARD;
> > +
> > +	if (WARN_ON_ONCE_RM(mm_iommu_ua_to_hpa_rm(mem, ua, &hpa)))
> > +		return H_HARDWARE;
> > +
> > +	pua = (void *) vmalloc_to_phys(pua);
> > +	if (WARN_ON_ONCE_RM(!pua))
> > +		return H_HARDWARE;
> > +
> > +	if (WARN_ON_ONCE_RM(mm_iommu_mapped_inc(mem)))
> > +		return H_CLOSED;
> > +
> > +	ret = iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
> > +	if (ret) {
> > +		mm_iommu_mapped_dec(mem);
> > +		/*
> > +		 * real mode xchg can fail if struct page crosses
> > +		 * a page boundary
> > +		 */
> > +		return H_TOO_HARD;
> > +	}
> > +
> > +	if (dir != DMA_NONE)
> > +		kvmppc_rm_tce_iommu_mapped_dec(kvm, tbl, entry);
> > +
> > +	*pua = ua;
> > +
> > +	return 0;
> > +}
> > +
> >  long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> >  		unsigned long ioba, unsigned long tce)
> >  {
> >  	struct kvmppc_spapr_tce_table *stt;
> >  	long ret;
> > +	struct kvmppc_spapr_tce_iommu_table *stit;
> > +	unsigned long entry, ua = 0;
> > +	enum dma_data_direction dir;
> >  
> >  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
> >  	/* 	    liobn, ioba, tce); */
> > @@ -182,7 +313,32 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> >  	if (ret != H_SUCCESS)
> >  		return ret;
> >  
> > -	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
> > +	dir = iommu_tce_direction(tce);
> > +	if ((dir != DMA_NONE) && kvmppc_gpa_to_ua(vcpu->kvm,
> > +			tce & ~(TCE_PCI_READ | TCE_PCI_WRITE), &ua, NULL))
> > +		return H_PARAMETER;
> > +
> > +	entry = ioba >> stt->page_shift;
> > +
> > +	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> > +		if (dir == DMA_NONE)
> > +			ret = kvmppc_rm_tce_iommu_unmap(vcpu->kvm,
> > +					stit->tbl, entry);
> > +		else
> > +			ret = kvmppc_rm_tce_iommu_map(vcpu->kvm,
> > +					stit->tbl, entry, ua, dir);
> > +
> > +		if (ret == H_SUCCESS)
> > +			continue;
> > +
> > +		if (ret == H_TOO_HARD)
> > +			return ret;
> > +
> > +		WARN_ON_ONCE_RM(1);
> > +		kvmppc_rm_clear_tce(stit->tbl, entry);
> > +	}
> > +
> > +	kvmppc_tce_put(stt, entry, tce);
> >  
> >  	return H_SUCCESS;
> >  }
> > @@ -223,6 +379,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >  	unsigned long tces, entry, ua = 0;
> >  	unsigned long *rmap = NULL;
> >  	bool prereg = false;
> > +	struct kvmppc_spapr_tce_iommu_table *stit;
> >  
> >  	stt = kvmppc_find_table(vcpu->kvm, liobn);
> >  	if (!stt)
> > @@ -270,6 +427,8 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >  			return H_TOO_HARD;
> >  
> >  		rmap = (void *) vmalloc_to_phys(rmap);
> > +		if (WARN_ON_ONCE_RM(!rmap))
> > +			return H_HARDWARE;
> >  
> >  		/*
> >  		 * Synchronize with the MMU notifier callbacks in
> > @@ -293,6 +452,27 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >  		if (ret != H_SUCCESS)
> >  			goto unlock_exit;
> >  
> > +		ua = 0;
> > +		if (kvmppc_gpa_to_ua(vcpu->kvm,
> > +				tce & ~(TCE_PCI_READ | TCE_PCI_WRITE),
> > +				&ua, NULL))
> > +			return H_PARAMETER;
> > +
> > +		list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> > +			ret = kvmppc_rm_tce_iommu_map(vcpu->kvm,
> > +					stit->tbl, entry + i, ua,
> > +					iommu_tce_direction(tce));
> > +
> > +			if (ret == H_SUCCESS)
> > +				continue;
> > +
> > +			if (ret == H_TOO_HARD)
> > +				goto unlock_exit;
> > +
> > +			WARN_ON_ONCE_RM(1);
> > +			kvmppc_rm_clear_tce(stit->tbl, entry);
> > +		}
> > +
> >  		kvmppc_tce_put(stt, entry + i, tce);
> >  	}
> >  
> > @@ -309,6 +489,7 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
> >  {
> >  	struct kvmppc_spapr_tce_table *stt;
> >  	long i, ret;
> > +	struct kvmppc_spapr_tce_iommu_table *stit;
> >  
> >  	stt = kvmppc_find_table(vcpu->kvm, liobn);
> >  	if (!stt)
> > @@ -322,6 +503,24 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
> >  	if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
> >  		return H_PARAMETER;
> >  
> > +	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> > +		unsigned long entry = ioba >> stit->tbl->it_page_shift;
> > +
> > +		for (i = 0; i < npages; ++i) {
> > +			ret = kvmppc_rm_tce_iommu_unmap(vcpu->kvm,
> > +					stit->tbl, entry + i);
> > +
> > +			if (ret == H_SUCCESS)
> > +				continue;
> > +
> > +			if (ret == H_TOO_HARD)
> > +				return ret;
> > +
> > +			WARN_ON_ONCE_RM(1);
> > +			kvmppc_rm_clear_tce(stit->tbl, entry);
> > +		}
> > +	}
> > +
> >  	for (i = 0; i < npages; ++i, ioba += (1ULL << stt->page_shift))
> >  		kvmppc_tce_put(stt, ioba >> stt->page_shift, tce_value);
> >  
> > diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> > index 95c91a9de351..62bdd6c48107 100644
> > --- a/arch/powerpc/kvm/powerpc.c
> > +++ b/arch/powerpc/kvm/powerpc.c
> > @@ -538,6 +538,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >  #ifdef CONFIG_PPC_BOOK3S_64
> >  	case KVM_CAP_SPAPR_TCE:
> >  	case KVM_CAP_SPAPR_TCE_64:
> > +		/* fallthrough */
> > +	case KVM_CAP_SPAPR_TCE_VFIO:
> >  	case KVM_CAP_PPC_RTAS:
> >  	case KVM_CAP_PPC_FIXUP_HCALL:
> >  	case KVM_CAP_PPC_ENABLE_HCALL:
> > diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> > index d32f239eb471..2b7dc22265fe 100644
> > --- a/virt/kvm/vfio.c
> > +++ b/virt/kvm/vfio.c
> > @@ -20,6 +20,10 @@
> >  #include <linux/vfio.h>
> >  #include "vfio.h"
> >  
> > +#ifdef CONFIG_SPAPR_TCE_IOMMU
> > +#include <asm/kvm_ppc.h>
> > +#endif
> > +
> >  struct kvm_vfio_group {
> >  	struct list_head node;
> >  	struct vfio_group *vfio_group;
> > @@ -211,6 +215,9 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
> >  
> >  		mutex_unlock(&kv->lock);
> >  
> > +#ifdef CONFIG_SPAPR_TCE_IOMMU
> > +		kvm_spapr_tce_release_iommu_group(dev->kvm, vfio_group);
> > +#endif
> >  		kvm_vfio_group_set_kvm(vfio_group, NULL);
> >  
> >  		kvm_vfio_group_put_external_user(vfio_group);
> > @@ -218,6 +225,53 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
> >  		kvm_vfio_update_coherency(dev);
> >  
> >  		return ret;
> > +
> > +#ifdef CONFIG_SPAPR_TCE_IOMMU
> > +	case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: {
> > +		struct kvm_vfio_spapr_tce param;
> > +		unsigned long minsz;
> > +		struct kvm_vfio *kv = dev->private;
> > +		struct vfio_group *vfio_group;
> > +		struct kvm_vfio_group *kvg;
> > +		struct fd f;
> > +
> > +		minsz = offsetofend(struct kvm_vfio_spapr_tce, tablefd);
> > +
> > +		if (copy_from_user(&param, (void __user *)arg, minsz))
> > +			return -EFAULT;
> > +
> > +		if (param.argsz < minsz || param.flags)
> > +			return -EINVAL;
> > +
> > +		f = fdget(param.groupfd);
> > +		if (!f.file)
> > +			return -EBADF;
> > +
> > +		vfio_group = kvm_vfio_group_get_external_user(f.file);
> > +		fdput(f);
> > +
> > +		if (IS_ERR(vfio_group))
> > +			return PTR_ERR(vfio_group);
> > +
> > +		ret = -ENOENT;
> > +
> > +		mutex_lock(&kv->lock);
> > +
> > +		list_for_each_entry(kvg, &kv->group_list, node) {
> > +			if (kvg->vfio_group != vfio_group)
> > +				continue;
> > +
> > +			ret = kvm_spapr_tce_attach_iommu_group(dev->kvm,
> > +					param.tablefd, vfio_group);
> > +
> > +			break;
> > +		}
> > +
> > +		mutex_unlock(&kv->lock);
> > +
> > +		return ret;
> > +	}
> > +#endif /* CONFIG_SPAPR_TCE_IOMMU */
> 
> 
> The group reference is leaked if kvm_spapr_tce_attach_iommu_group()
> fails.

Good catch.

> My preference would be to not hold that separate group
> reference in the spapr code anyway, having a parallel life cycle over
> there is confusing and results in ugliness like duplicating 
> kvm_vfio_group_put_external_user().  Thanks,
> 
> Alex
> 
> >  	}
> >  
> >  	return -ENXIO;
> > @@ -242,6 +296,9 @@ static int kvm_vfio_has_attr(struct kvm_device *dev,
> >  		switch (attr->attr) {
> >  		case KVM_DEV_VFIO_GROUP_ADD:
> >  		case KVM_DEV_VFIO_GROUP_DEL:
> > +#ifdef CONFIG_SPAPR_TCE_IOMMU
> > +		case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
> > +#endif
> >  			return 0;
> >  		}
> >  
> > @@ -257,6 +314,9 @@ static void kvm_vfio_destroy(struct kvm_device *dev)
> >  	struct kvm_vfio_group *kvg, *tmp;
> >  
> >  	list_for_each_entry_safe(kvg, tmp, &kv->group_list, node) {
> > +#ifdef CONFIG_SPAPR_TCE_IOMMU
> > +		kvm_spapr_tce_release_iommu_group(dev->kvm, kvg->vfio_group);
> > +#endif
> >  		kvm_vfio_group_set_kvm(kvg->vfio_group, NULL);
> >  		kvm_vfio_group_put_external_user(kvg->vfio_group);
> >  		list_del(&kvg->node);
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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