Subject: Re: [PATCH kernel v3] KVM: PPC: Add in-kernel acceleration for VFIO

From: David Gibson <[email-masked]>
Date: Fri, 13 Jan 2017 13:38:52 +1100

On Fri, Jan 13, 2017 at 01:23:46PM +1100, Alexey Kardashevskiy wrote:
> On 13/01/17 10:53, David Gibson wrote:
> > On Thu, Jan 12, 2017 at 07:09:01PM +1100, Alexey Kardashevskiy wrote:
> >> On 12/01/17 16:04, David Gibson wrote:
> >>> On Tue, Dec 20, 2016 at 05:52:29PM +1100, Alexey Kardashevskiy 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.
> >>>>
> >>>> 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, this is done to simplify the cleanup and can be
> >>>> improved later.
> >>>>
> >>>> This advertises the new KVM_CAP_SPAPR_TCE_VFIO capability to the user
> >>>> space.
> >>>>
> >>>> 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 <[email-masked]>
> >>>> ---
> >>>> Changes:
> >>>> 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
> >>>> ---
> >>>>
> >>>> This obsoletes:
> >>>>
> >>>> [PATCH kernel v2 08/11] KVM: PPC: Pass kvm* to kvmppc_find_table()
> >>>> [PATCH kernel v2 09/11] vfio iommu: Add helpers to (un)register blocking notifiers per group
> >>>> [PATCH kernel v2 11/11] KVM: PPC: Add in-kernel acceleration for VFIO
> >>>>
> >>>>
> >>>> So I have not reposted the whole thing, should have I?
> >>>>
> >>>>
> >>>> btw "F:     virt/kvm/vfio.*"  is missing MAINTAINERS.
> >>>>
> >>>>
> >>>> ---
> >>>>  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           | 286 +++++++++++++++++++++++++++++
> >>>>  arch/powerpc/kvm/book3s_64_vio_hv.c        | 178 ++++++++++++++++++
> >>>>  arch/powerpc/kvm/powerpc.c                 |   2 +
> >>>>  virt/kvm/vfio.c                            |  88 +++++++++
> >>>>  8 files changed, 594 insertions(+), 2 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;
> >>>> +	@flags are not supported now, must be zero;
> >>>> +	@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 28350a294b1e..3d281b7ea369 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 0a21c8503974..936138b866e7 100644
> >>>> --- a/arch/powerpc/include/asm/kvm_ppc.h
> >>>> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> >>>> @@ -163,6 +163,10 @@ 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, struct iommu_group *grp);
> >>>> +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 810f74317987..4088da4a575f 100644
> >>>> --- a/include/uapi/linux/kvm.h
> >>>> +++ b/include/uapi/linux/kvm.h
> >>>> @@ -1068,6 +1068,7 @@ 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,
> >>>> @@ -1089,6 +1090,13 @@ 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 15df8ae627d9..008c4aee4df6 100644
> >>>> --- a/arch/powerpc/kvm/book3s_64_vio.c
> >>>> +++ b/arch/powerpc/kvm/book3s_64_vio.c
> >>>> @@ -27,6 +27,10 @@
> >>>>  #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>
> >>>> @@ -39,6 +43,20 @@
> >>>>  #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 (!fn)
> >>>
> >>> I think this should have a WARN_ON().  If the vfio module is gone
> >>> while you still have VFIO groups attached to a KVM table, something
> >>> has gone horribly wrong.
> >>>
> >>>> +		return;
> >>>> +
> >>>> +	fn(vfio_group);
> >>>> +
> >>>> +	symbol_put(vfio_group_put_external_user);
> >>>> +}
> >>>>  
> >>>>  static unsigned long kvmppc_tce_pages(unsigned long iommu_pages)
> >>>>  {
> >>>> @@ -90,6 +108,99 @@ 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);
> >>>> +
> >>>> +	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);
> >>>> +
> >>>> +		iommu_table_put(stit->tbl);
> >>>> +		kvm_vfio_group_put_external_user(stit->group);
> >>>> +
> >>>> +		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 iommu_group *grp)
> >>>
> >>> Isn't passing both the vfio_group and the iommu_group redundant?
> >>
> >> vfio_group struct is internal to the vfio driver and there is no API to get
> >> the iommu_group pointer from it.
> > 
> > But in the caller you *do* derive the group from the vfio group by
> > going via id (ugly, but workable I guess).  Why not fold that logic
> > into this function.
> 
> 
> I could, either way looks equally ugly-ish to me, rework it?

Yes please, it makes more sense having the ugly lookup within the function.

> >>>> +{
> >>>> +	struct kvmppc_spapr_tce_table *stt = NULL;
> >>>> +	bool found = false;
> >>>> +	struct iommu_table *tbl = NULL;
> >>>> +	struct iommu_table_group *table_group;
> >>>> +	long i;
> >>>> +	struct kvmppc_spapr_tce_iommu_table *stit;
> >>>> +	struct fd f;
> >>>> +
> >>>> +	f = fdget(tablefd);
> >>>> +	if (!f.file)
> >>>> +		return -EBADF;
> >>>> +
> >>>> +	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)
> >>>> +		return -ENODEV;
> >>>
> >>> Not entirely sure if ENODEV is the right error, but I can't
> >>> immediately think of a better one.
> 
> 
> btw I still do not have a better candidate, can I keep this as is?

Yes, that's ok.

> >>>
> >>>> +	table_group = iommu_group_get_iommudata(grp);
> >>>> +	if (!table_group)
> >>>> +		return -EFAULT;
> >>>
> >>> EFAULT is usually only returned when you pass a syscall a bad pointer,
> >>> which doesn't look to be the case here.  What situation does this
> >>> error path actually represent?
> >>
> >>
> >> "something went terribly wrong".
> > 
> > In that case there should be a WARN_ON().  As long as it's something
> > terribly wrong that can't be the user's fault.
> > 
> >>>> +
> >>>> +	for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
> >>>> +		struct iommu_table *tbltmp = table_group->tables[i];
> >>>> +
> >>>> +		if (!tbltmp)
> >>>> +			continue;
> >>>> +
> >>>> +		if ((tbltmp->it_page_shift == stt->page_shift) &&
> >>>> +				(tbltmp->it_offset == stt->offset)) {
> >>>> +			tbl = tbltmp;
> >>>> +			break;
> >>>> +		}
> >>>> +	}
> >>>> +	if (!tbl)
> >>>> +		return -ENODEV;
> >>>> +
> >>>> +	iommu_table_get(tbl);
> >>>> +
> >>>> +	stit = kzalloc(sizeof(*stit), GFP_KERNEL);
> >>>> +	stit->tbl = tbl;
> >>>> +	stit->group = group;
> >>>> +
> >>>> +	list_add_rcu(&stit->next, &stt->iommu_tables);
> >>>
> >>> Won't this add a separate stit entry for each group attached to the
> >>> LIOBN, even if those groups share a single hardware iommu table -
> >>> which is the likely case if those groups have all been put into the
> >>> same container.
> >>
> >>
> >> Correct. I am planning on optimizing this later.
> > 
> > Hmm, ok.
> > 
> >>>> +	return 0;
> >>>> +}
> >>>> +
> >>>>  static void release_spapr_tce_table(struct rcu_head *head)
> >>>>  {
> >>>>  	struct kvmppc_spapr_tce_table *stt = container_of(head,
> >>>> @@ -132,6 +243,8 @@ 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(
> >>>> @@ -181,6 +294,7 @@ 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);
> >>>> @@ -209,11 +323,161 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> >>>>  	return ret;
> >>>>  }
> >>>>  
> >>>> +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)
> >>>> +		return H_HARDWARE;
> >>>> +
> >>>> +	mem = mm_iommu_lookup(kvm->mm, *pua, pgsize);
> >>>> +	if (!mem)
> >>>> +		return H_HARDWARE;
> >>>
> >>> IIUC, this error represents trying to unmap a page from the vIOMMU,
> >>> and discovering that it wasn't preregistered in the first place, which
> >>> shouldn't happen.  So would a WARN_ON() make sense here as well as the
> >>> H_HARDWARE.
> >>>
> >>>> +	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;
> >>>> +
> >>>> +	if (iommu_tce_xchg(tbl, entry, &hpa, &dir))
> >>>> +		return H_HARDWARE;
> >>>> +
> >>>> +	if (dir == DMA_NONE)
> >>>> +		return H_SUCCESS;
> >>>> +
> >>>> +	return kvmppc_tce_iommu_mapped_dec(kvm, tbl, entry);
> >>>> +}
> >>>> +
> >>>> +long kvmppc_tce_iommu_map(struct kvm *kvm, struct iommu_table *tbl,
> >>>> +		unsigned long entry, unsigned long gpa,
> >>>> +		enum dma_data_direction dir)
> >>>> +{
> >>>> +	long ret;
> >>>> +	unsigned long hpa, ua, *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;
> >>>> +
> >>>> +	if (kvmppc_gpa_to_ua(kvm, gpa, &ua, NULL))
> >>>> +		return H_HARDWARE;
> >>>
> >>> This would represent the guest trying to map a mad GPA, yes?  In which
> >>> case H_HARDWARE doesn't seem right.  H_PARAMETER or H_PERMISSION, maybe.
> >>>
> >>>> +	mem = mm_iommu_lookup(kvm->mm, ua, 1ULL << tbl->it_page_shift);
> >>>> +	if (!mem)
> >>>> +		return H_HARDWARE;
> >>>
> >>> Here H_HARDWARE seems right. IIUC this represents the guest trying to
> >>> map an address which wasn't pre-registered.  That would indicate a bug
> >>> in qemu, which is hardware as far as the guest is concerned.
> >>>
> >>>> +
> >>>> +	if (mm_iommu_ua_to_hpa(mem, ua, &hpa))
> >>>> +		return H_HARDWARE;
> >>>
> >>> Not sure what this case represents.
> >>
> >> Preregistered memory not being able to translate userspace address to a
> >> host physical. In virtual mode it is a simple bounds checker, in real mode
> >> it also includes vmalloc_to_phys() failure.
> > 
> > Ok.  This caller is virtual mode only, isn't it?  If we fail the
> > bounds check, that sounds like a WARN_ON() + H_HARDWARE, since it
> > means we've translated the GPA to an insane UA.
> > 
> > If the translation just fails, that sounds like an H_TOO_HARD.
> > 
> >>>> +	if (mm_iommu_mapped_inc(mem))
> >>>> +		return H_HARDWARE;
> >>>
> >>> Or this.
> >>
> >> A preregistered memory area is in a process of disposal, no new mappings
> >> are allowed.
> > 
> > Ok, again under control of qemu, so H_HARDWARE is reasonable.
> > 
> >>>> +	ret = iommu_tce_xchg(tbl, entry, &hpa, &dir);
> >>>> +	if (ret) {
> >>>> +		mm_iommu_mapped_dec(mem);
> >>>> +		return H_TOO_HARD;
> >>>> +	}
> >>>> +
> >>>> +	if (dir != DMA_NONE)
> >>>> +		kvmppc_tce_iommu_mapped_dec(kvm, tbl, entry);
> >>>> +
> >>>> +	*pua = ua;
> >>>> +
> >>>> +	return 0;
> >>>> +}
> >>>> +
> >>>> +long kvmppc_h_put_tce_iommu(struct kvm_vcpu *vcpu,
> >>>> +		struct iommu_table *tbl,
> >>>> +		unsigned long liobn, unsigned long ioba,
> >>>> +		unsigned long tce)
> >>>> +{
> >>>> +	long idx, ret = H_HARDWARE;
> >>>> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> >>>> +	const unsigned long gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> >>>> +	const enum dma_data_direction dir = iommu_tce_direction(tce);
> >>>> +
> >>>> +	/* Clear TCE */
> >>>> +	if (dir == DMA_NONE) {
> >>>> +		if (iommu_tce_clear_param_check(tbl, ioba, 0, 1))
> >>>> +			return H_PARAMETER;
> >>>> +
> >>>> +		return kvmppc_tce_iommu_unmap(vcpu->kvm, tbl, entry);
> >>>> +	}
> >>>> +
> >>>> +	/* Put TCE */
> >>>> +	if (iommu_tce_put_param_check(tbl, ioba, gpa))
> >>>> +		return H_PARAMETER;
> >>>> +
> >>>> +	idx = srcu_read_lock(&vcpu->kvm->srcu);
> >>>> +	ret = kvmppc_tce_iommu_map(vcpu->kvm, tbl, entry, gpa, dir);
> >>>> +	srcu_read_unlock(&vcpu->kvm->srcu, idx);
> >>>> +
> >>>> +	return ret;
> >>>> +}
> >>>> +
> >>>> +static long kvmppc_h_put_tce_indirect_iommu(struct kvm_vcpu *vcpu,
> >>>> +		struct iommu_table *tbl, unsigned long ioba,
> >>>> +		u64 __user *tces, unsigned long npages)
> >>>> +{
> >>>> +	unsigned long i, ret, tce, gpa;
> >>>> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> >>>> +
> >>>> +	for (i = 0; i < npages; ++i) {
> >>>> +		gpa = be64_to_cpu(tces[i]) & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> >>>
> >>> IIUC this is the virtual mode, not the real mode version.  In which
> >>> case you shouldn't be accessing tces[i] (a userspace pointeR) directly
> >>> bit should instead be using get_user().
> >>>
> >>>> +		if (iommu_tce_put_param_check(tbl, ioba +
> >>>> +				(i << tbl->it_page_shift), gpa))
> >>>> +			return H_PARAMETER;
> >>>> +	}
> >>>> +
> >>>> +	for (i = 0; i < npages; ++i) {
> >>>> +		tce = be64_to_cpu(tces[i]);
> >>>> +		gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> >>>> +
> >>>> +		ret = kvmppc_tce_iommu_map(vcpu->kvm, tbl, entry + i, gpa,
> >>>> +				iommu_tce_direction(tce));
> >>>> +		if (ret != H_SUCCESS)
> >>>> +			return ret;
> >>>> +	}
> >>>> +
> >>>> +	return H_SUCCESS;
> >>>> +}
> >>>> +
> >>>> +long kvmppc_h_stuff_tce_iommu(struct kvm_vcpu *vcpu,
> >>>> +		struct iommu_table *tbl,
> >>>> +		unsigned long liobn, unsigned long ioba,
> >>>> +		unsigned long tce_value, unsigned long npages)
> >>>> +{
> >>>> +	unsigned long i;
> >>>> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> >>>> +
> >>>> +	if (iommu_tce_clear_param_check(tbl, ioba, tce_value, npages))
> >>>> +		return H_PARAMETER;
> >>>> +
> >>>> +	for (i = 0; i < npages; ++i)
> >>>> +		kvmppc_tce_iommu_unmap(vcpu->kvm, tbl, entry + i);
> >>>> +
> >>>> +	return H_SUCCESS;
> >>>> +}
> >>>> +
> >>>>  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;
> >>>> +	struct kvmppc_spapr_tce_iommu_table *stit;
> >>>>  
> >>>>  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
> >>>>  	/* 	    liobn, ioba, tce); */
> >>>> @@ -230,6 +494,12 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> >>>>  	if (ret != H_SUCCESS)
> >>>>  		return ret;
> >>>>  
> >>>> +	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> >>>
> >>> As noted above, AFAICT there is one stit per group, rather than per
> >>> backend IOMMU table, so if there are multiple groups in the same
> >>> container (and therefore attached to the same LIOBN), won't this mean
> >>> we duplicate this operation a bunch of times?
> >>>
> >>>> +		ret = kvmppc_h_put_tce_iommu(vcpu, stit->tbl, liobn, ioba, tce);
> >>>> +		if (ret != H_SUCCESS)
> >>>> +			return ret;
> >>>> +	}
> >>>> +
> >>>>  	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
> >>>>  
> >>>>  	return H_SUCCESS;
> >>>> @@ -245,6 +515,7 @@ 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)
> >>>> @@ -272,6 +543,13 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >>>>  	}
> >>>>  	tces = (u64 __user *) ua;
> >>>>  
> >>>> +	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> >>>> +		ret = kvmppc_h_put_tce_indirect_iommu(vcpu,
> >>>> +				stit->tbl, ioba, tces, npages);
> >>>> +		if (ret != H_SUCCESS)
> >>>> +			goto unlock_exit;
> >>>
> >>> Hmm, I don't suppose you could simplify things by not having a
> >>> put_tce_indirect() version of the whole backend iommu mapping
> >>> function, but just a single-TCE version, and instead looping across
> >>> the backend IOMMU tables as you put each indirect entry in .
> >>>
> >>>> +	}
> >>>> +
> >>>>  	for (i = 0; i < npages; ++i) {
> >>>>  		if (get_user(tce, tces + i)) {
> >>>>  			ret = H_TOO_HARD;
> >>>> @@ -299,6 +577,7 @@ 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)
> >>>> @@ -312,6 +591,13 @@ 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) {
> >>>> +		ret = kvmppc_h_stuff_tce_iommu(vcpu, stit->tbl, liobn, ioba,
> >>>> +				tce_value, npages);
> >>>> +		if (ret != H_SUCCESS)
> >>>> +			return ret;
> >>>> +	}
> >>>> +
> >>>>  	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 8a6834e6e1c8..4d6f01712a6d 100644
> >>>> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
> >>>> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
> >>>> @@ -190,11 +190,165 @@ static struct mm_iommu_table_group_mem_t *kvmppc_rm_iommu_lookup(
> >>>>  	return mm_iommu_lookup_rm(vcpu->kvm->mm, ua, size);
> >>>>  }
> >>>>  
> >>>> +static long kvmppc_rm_tce_iommu_mapped_dec(struct kvm_vcpu *vcpu,
> >>>> +		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)
> >>>> +		return H_SUCCESS;
> >>>
> >>> What case is this?  Not being able to find the userspace duesn't sound
> >>> like a success.
> >>>
> >>>> +	pua = (void *) vmalloc_to_phys(pua);
> >>>> +	if (!pua)
> >>>> +		return H_SUCCESS;
> >>>
> >>> And again..
> >>>
> >>>> +	mem = kvmppc_rm_iommu_lookup(vcpu, *pua, pgsize);
> >>>> +	if (!mem)
> >>>> +		return H_HARDWARE;
> >>>
> >>> Should this have a WARN_ON?
> >>>
> >>>> +	mm_iommu_mapped_dec(mem);
> >>>> +
> >>>> +	*pua = 0;
> >>>> +
> >>>> +	return H_SUCCESS;
> >>>> +}
> >>>> +
> >>>> +static long kvmppc_rm_tce_iommu_unmap(struct kvm_vcpu *vcpu,
> >>>> +		struct iommu_table *tbl, unsigned long entry)
> >>>> +{
> >>>> +	enum dma_data_direction dir = DMA_NONE;
> >>>> +	unsigned long hpa = 0;
> >>>> +
> >>>> +	if (iommu_tce_xchg_rm(tbl, entry, &hpa, &dir))
> >>>> +		return H_HARDWARE;
> >>>> +
> >>>> +	if (dir == DMA_NONE)
> >>>> +		return H_SUCCESS;
> >>>> +
> >>>> +	return kvmppc_rm_tce_iommu_mapped_dec(vcpu, tbl, entry);
> >>>> +}
> >>>> +
> >>>> +long kvmppc_rm_tce_iommu_map(struct kvm_vcpu *vcpu, struct iommu_table *tbl,
> >>>> +		unsigned long entry, unsigned long gpa,
> >>>> +		enum dma_data_direction dir)
> >>>> +{
> >>>> +	long ret;
> >>>> +	unsigned long hpa = 0, ua;
> >>>> +	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;
> >>>> +
> >>>> +	if (kvmppc_gpa_to_ua(vcpu->kvm, gpa, &ua, NULL))
> >>>> +		return H_HARDWARE;
> >>>
> >>> Again H_HARDWARE doesn't seem right here.
> >>>
> >>>> +	mem = kvmppc_rm_iommu_lookup(vcpu, ua, 1ULL << tbl->it_page_shift);
> >>>> +	if (!mem)
> >>>> +		return H_HARDWARE;
> >>>> +
> >>>> +	if (mm_iommu_ua_to_hpa_rm(mem, ua, &hpa))
> >>>> +		return H_HARDWARE;
> >>>> +
> >>>> +	pua = (void *) vmalloc_to_phys(pua);
> >>>> +	if (!pua)
> >>>> +		return H_HARDWARE;
> >>>> +
> >>>> +	if (mm_iommu_mapped_inc(mem))
> >>>> +		return H_HARDWARE;
> >>>> +
> >>>> +	ret = iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
> >>>> +	if (ret) {
> >>>> +		mm_iommu_mapped_dec(mem);
> >>>> +		return H_TOO_HARD;
> >>>> +	}
> >>>> +
> >>>> +	if (dir != DMA_NONE)
> >>>> +		kvmppc_rm_tce_iommu_mapped_dec(vcpu, tbl, entry);
> >>>> +
> >>>> +	*pua = ua;
> >>>> +
> >>>> +	return 0;
> >>>> +}
> >>>> +EXPORT_SYMBOL_GPL(kvmppc_rm_tce_iommu_map);
> >>>> +
> >>>> +static long kvmppc_rm_h_put_tce_iommu(struct kvm_vcpu *vcpu,
> >>>> +		struct iommu_table *tbl, unsigned long liobn,
> >>>> +		unsigned long ioba, unsigned long tce)
> >>>> +{
> >>>> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> >>>> +	const unsigned long gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> >>>> +	const enum dma_data_direction dir = iommu_tce_direction(tce);
> >>>> +
> >>>> +	/* Clear TCE */
> >>>> +	if (dir == DMA_NONE) {
> >>>> +		if (iommu_tce_clear_param_check(tbl, ioba, 0, 1))
> >>>> +			return H_PARAMETER;
> >>>> +
> >>>> +		return kvmppc_rm_tce_iommu_unmap(vcpu, tbl, entry);
> >>>> +	}
> >>>> +
> >>>> +	/* Put TCE */
> >>>> +	if (iommu_tce_put_param_check(tbl, ioba, gpa))
> >>>> +		return H_PARAMETER;
> >>>> +
> >>>> +	return kvmppc_rm_tce_iommu_map(vcpu, tbl, entry, gpa, dir);
> >>>> +}
> >>>> +
> >>>> +static long kvmppc_rm_h_put_tce_indirect_iommu(struct kvm_vcpu *vcpu,
> >>>> +		struct iommu_table *tbl, unsigned long ioba,
> >>>> +		u64 *tces, unsigned long npages)
> >>>> +{
> >>>> +	unsigned long i, ret, tce, gpa;
> >>>> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> >>>> +
> >>>> +	for (i = 0; i < npages; ++i) {
> >>>> +		gpa = be64_to_cpu(tces[i]) & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> >>>> +
> >>>> +		if (iommu_tce_put_param_check(tbl, ioba +
> >>>> +				(i << tbl->it_page_shift), gpa))
> >>>> +			return H_PARAMETER;
> >>>> +	}
> >>>> +
> >>>> +	for (i = 0; i < npages; ++i) {
> >>>> +		tce = be64_to_cpu(tces[i]);
> >>>> +		gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> >>>> +
> >>>> +		ret = kvmppc_rm_tce_iommu_map(vcpu, tbl, entry + i, gpa,
> >>>> +				iommu_tce_direction(tce));
> >>>> +		if (ret != H_SUCCESS)
> >>>> +			return ret;
> >>>> +	}
> >>>> +
> >>>> +	return H_SUCCESS;
> >>>> +}
> >>>> +
> >>>> +static long kvmppc_rm_h_stuff_tce_iommu(struct kvm_vcpu *vcpu,
> >>>> +		struct iommu_table *tbl,
> >>>> +		unsigned long liobn, unsigned long ioba,
> >>>> +		unsigned long tce_value, unsigned long npages)
> >>>> +{
> >>>> +	unsigned long i;
> >>>> +	const unsigned long entry = ioba >> tbl->it_page_shift;
> >>>> +
> >>>> +	if (iommu_tce_clear_param_check(tbl, ioba, tce_value, npages))
> >>>> +		return H_PARAMETER;
> >>>> +
> >>>> +	for (i = 0; i < npages; ++i)
> >>>> +		kvmppc_rm_tce_iommu_unmap(vcpu, tbl, entry + i);
> >>>> +
> >>>> +	return H_SUCCESS;
> >>>> +}
> >>>> +
> >>>>  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;
> >>>>  
> >>>>  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
> >>>>  	/* 	    liobn, ioba, tce); */
> >>>> @@ -211,6 +365,13 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
> >>>>  	if (ret != H_SUCCESS)
> >>>>  		return ret;
> >>>>  
> >>>> +	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> >>>> +		ret = kvmppc_rm_h_put_tce_iommu(vcpu, stit->tbl,
> >>>> +				liobn, ioba, tce);
> >>>> +		if (ret != H_SUCCESS)
> >>>> +			return ret;
> >>>> +	}
> >>>> +
> >>>>  	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
> >>>>  
> >>>>  	return H_SUCCESS;
> >>>> @@ -278,6 +439,7 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >>>>  		 * depend on hpt.
> >>>>  		 */
> >>>>  		struct mm_iommu_table_group_mem_t *mem;
> >>>> +		struct kvmppc_spapr_tce_iommu_table *stit;
> >>>>  
> >>>>  		if (kvmppc_gpa_to_ua(vcpu->kvm, tce_list, &ua, NULL))
> >>>>  			return H_TOO_HARD;
> >>>> @@ -285,6 +447,13 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
> >>>>  		mem = kvmppc_rm_iommu_lookup(vcpu, ua, IOMMU_PAGE_SIZE_4K);
> >>>>  		if (!mem || mm_iommu_ua_to_hpa_rm(mem, ua, &tces))
> >>>>  			return H_TOO_HARD;
> >>>> +
> >>>> +		list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
> >>>> +			ret = kvmppc_rm_h_put_tce_indirect_iommu(vcpu,
> >>>> +					stit->tbl, ioba, (u64 *)tces, npages);
> >>>> +			if (ret != H_SUCCESS)
> >>>> +				return ret;
> >>>> +		}
> >>>>  	} else {
> >>>>  		/*
> >>>>  		 * This is emulated devices case.
> >>>> @@ -334,6 +503,8 @@ 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)
> >>>> @@ -347,6 +518,13 @@ 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) {
> >>>> +		ret = kvmppc_rm_h_stuff_tce_iommu(vcpu, stit->tbl,
> >>>> +				liobn, ioba, tce_value, npages);
> >>>> +		if (ret != H_SUCCESS)
> >>>> +			return ret;
> >>>> +	}
> >>>> +
> >>>>  	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 70963c845e96..0e555ba998c0 100644
> >>>> --- a/arch/powerpc/kvm/powerpc.c
> >>>> +++ b/arch/powerpc/kvm/powerpc.c
> >>>> @@ -536,6 +536,8 @@ 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_ALLOC_HTAB:
> >>>>  	case KVM_CAP_PPC_RTAS:
> >>>>  	case KVM_CAP_PPC_FIXUP_HCALL:
> >>>> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> >>>> index d32f239eb471..3181054c8ff7 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;
> >>>> @@ -89,6 +93,22 @@ static bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
> >>>>  	return ret > 0;
> >>>>  }
> >>>>  
> >>>> +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;
> >>>> +}
> >>>> +
> >>>>  /*
> >>>>   * Groups can use the same or different IOMMU domains.  If the same then
> >>>>   * adding a new group may change the coherency of groups we've previously
> >>>> @@ -211,6 +231,9 @@ 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 +241,65 @@ 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) {
> >>>> +			int group_id;
> >>>> +			struct iommu_group *grp;
> >>>> +
> >>>> +			if (kvg->vfio_group != vfio_group)
> >>>> +				continue;
> >>>> +
> >>>> +			group_id = kvm_vfio_external_user_iommu_id(
> >>>> +					kvg->vfio_group);
> >>>> +			grp = iommu_group_get_by_id(group_id);
> >>>> +			if (!grp) {
> >>>> +				ret = -EFAULT;
> >>>> +				break;
> >>>> +			}
> >>>> +
> >>>> +			ret = kvm_spapr_tce_attach_iommu_group(dev->kvm,
> >>>> +					param.tablefd, vfio_group, grp);
> >>>> +
> >>>> +			iommu_group_put(grp);
> >>>> +			break;
> >>>> +		}
> >>>> +
> >>>> +		mutex_unlock(&kv->lock);
> >>>> +
> >>>> +		return ret;
> >>>> +	}
> >>>> +#endif /* CONFIG_SPAPR_TCE_IOMMU */
> >>>>  	}
> >>>
> >>> Don't you also need to add something to the KVM_DEV_VFIO_GROUP_DEL
> >>> path to detach the group from all LIOBNs,  Or else just fail if if
> >>> there are LIOBNs attached.  I think it would be a qemu bug not to
> >>> detach the LIOBNs before removing the group, but we stil need to
> >>> protect the host in that case.
> >>
> >>
> >> Yeah, this bit is a bit tricky/ugly.
> >>
> >> kvm_spapr_tce_liobn_release_iommu_group() (called from
> >> kvm_spapr_tce_fops::release()) drops references when a group is removed
> >> from the VFIO KVM device so there is no KVM_DEV_VFIO_GROUP_UNSET_SPAPR_TCE
> >> and no action from QEMU is required.
> > 
> > IF qemu simply closes the group fd.  Which it does now, but might not
> > always.  You still need to deal with the case where userspace does a
> > KVM_DEV_VFIO_GROUP_DEL instead of closing the group fd.
> 
> 
> This patch adds kvm_spapr_tce_release_iommu_group() to the
> KVM_DEV_VFIO_GROUP_DEL handler.

It does? Oh.. I didn't spot that.

> 
> 
> 
> > 
> >>
> >>
> >>
> >>>>  
> >>>>  	return -ENXIO;
> >>>> @@ -242,6 +324,9 @@ 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 +342,9 @@ 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