Subject: Re: [PATCH kernel v4 10/10] KVM: PPC: VFIO: Add in-kernel acceleration for VFIO

From: David Gibson <[email-masked]>
Date: Thu, 9 Feb 2017 17:41:12 +1100

On Tue, Feb 07, 2017 at 06:17:11PM +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; 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 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:
> 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
> ---
> 
> This has separate copies of handlers for real and virtual modes as
> in fact H_PUT_TCE and H_STUFF_TCE could share a lot (common helpers
> would take a "realmode" flag) but H_PUT_TCE_INDIRECT uses get_user()
> in virtual mode and direct access in real mode and having a common
> helper for it would make things uglier imho.
> 
> 
> ---
>  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           | 319 ++++++++++++++++++++++++++++-
>  arch/powerpc/kvm/book3s_64_vio_hv.c        | 172 +++++++++++++++-
>  arch/powerpc/kvm/powerpc.c                 |   2 +
>  virt/kvm/vfio.c                            |  60 ++++++
>  8 files changed, 590 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;
> +	@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 e59b172666cd..a827006941f8 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 37bc9e7e90ba..da1410bd6b36 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);
> +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 a2c9bb5a0ead..cdfa01169bd2 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1076,6 +1076,7 @@ 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,
> @@ -1097,6 +1098,13 @@ 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 9a7b7fca5e84..cb0469151e35 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 +43,36 @@
>  #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;
> +}
>  
>  static unsigned long kvmppc_tce_pages(unsigned long iommu_pages)
>  {
> @@ -90,6 +124,123 @@ 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 (!grp)
> +		return -EFAULT;

EFAULT doesn't look right, that's usually means userspace has give us
a bad address.  What does failure to look up the iommu group by id
mean here?

> +
> +	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 = -ENODEV;

ENODEV doesn't look right either.  That generally means you're trying
to use a device or facility that doesn't exist.  This case just means
you've passed a file handle that either isn't a TCE table at all, or
os one associated with a different VM.  -EINVAL, I guess, overloaded
as it is.

> +		goto put_exit;

Don't you need to put the table fd as well as the iommu group which
you put in that exit path?

> +	}
> +
> +	table_group = iommu_group_get_iommudata(grp);
> +	if (WARN_ON(!table_group)) {
> +		ret = -EFAULT;
> +		goto put_exit;

Again don't you need to put the table fd as well.

> +	}
> +
> +	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 = -ENODEV;

Again, ENODEV doesn't seem right.  Here the problem is that the host
hardware constraints don't match the guest hardware constraints.
Hmm.  EIO?  ENOSPC?

> +		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);

So if you add the same group to the same liobn multiple times, you'll
get multiple identical entries in this list.

I guess that's mostly harmless... although.. does it allow the user to
force the allocation of arbitrary amounts of kernel memory in that
list?

> +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,
> @@ -132,6 +283,8 @@ 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 +334,7 @@ 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 +363,94 @@ 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;

What could trigger this error?  Should it be a WARN_ON?

> +	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 (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 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_PARAMETER;
> +
> +	mem = mm_iommu_lookup(kvm->mm, ua, 1ULL << tbl->it_page_shift);
> +	if (!mem)
> +		return H_TOO_HARD;
> +
> +	if (mm_iommu_ua_to_hpa(mem, ua, &hpa))
> +		return H_HARDWARE;

IIUC this would happen if qemu had failed to preregister all of guest
RAM, making this indeed an H_HARDWARE.

> +	if (mm_iommu_mapped_inc(mem))
> +		return H_HARDWARE;

I'm less clear on when this one would happen.

> +
> +	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(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, gpa;
> +	enum dma_data_direction dir;
>  
>  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
>  	/* 	    liobn, ioba, tce); */
> @@ -230,6 +467,36 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  	if (ret != H_SUCCESS)
>  		return ret;
>  
> +	stit = list_first_entry_or_null(&stt->iommu_tables,
> +			struct kvmppc_spapr_tce_iommu_table, next);
> +	if (stit) {
> +		entry = ioba >> stit->tbl->it_page_shift;
> +		gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +		dir = iommu_tce_direction(tce);
> +
> +		if (dir == DMA_NONE) {
> +			if (iommu_tce_clear_param_check(stit->tbl, ioba, 0, 1))
> +				return H_PARAMETER;
> +		} else {
> +			if (iommu_tce_put_param_check(stit->tbl, ioba, gpa))

Any way you could make these param check functions based on stt
instead of stit->tbl?  That would let you do them before checking if
there are any hw tables to update, avaoiding the somewhat awkward
	if (at least one)
		for (each one)
construct.

> +				return H_PARAMETER;
> +		}
> +
> +		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, gpa, dir);
> +				srcu_read_unlock(&vcpu->kvm->srcu, idx);
> +			}
> +			if (ret != H_SUCCESS)
> +				return ret;

Doesn't this error path need to clean up for the case where you
managed to update some backing TCE tables, but then failed later ones?

> +		}
> +	}
> +
>  	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
>  
>  	return H_SUCCESS;
> @@ -242,9 +509,10 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  {
>  	struct kvmppc_spapr_tce_table *stt;
>  	long i, ret = H_SUCCESS, idx;
> -	unsigned long entry, ua = 0;
> +	unsigned long entry, gpa, 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 +540,9 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  	}
>  	tces = (u64 __user *) ua;
>  
> +	stit = list_first_entry_or_null(&stt->iommu_tables,
> +			struct kvmppc_spapr_tce_iommu_table, next);
> +
>  	for (i = 0; i < npages; ++i) {
>  		if (get_user(tce, tces + i)) {
>  			ret = H_TOO_HARD;
> @@ -282,6 +553,15 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  		ret = kvmppc_tce_validate(stt, tce);
>  		if (ret != H_SUCCESS)
>  			goto unlock_exit;
> +
> +		if (stit) {
> +			gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +			ret = iommu_tce_put_param_check(stit->tbl,
> +					ioba + (i << stit->tbl->it_page_shift),
> +					gpa);
> +			if (ret != H_SUCCESS)
> +				goto unlock_exit;
> +		}
>  	}
>  
>  	for (i = 0; i < npages; ++i) {
> @@ -291,6 +571,21 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  		}
>  		tce = be64_to_cpu(tce);
>  
> +		if (stit) {
> +			for (i = 0; i < npages; ++i) {
> +				gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +
> +				list_for_each_entry_lockless(stit,
> +						&stt->iommu_tables, next) {
> +					ret = kvmppc_tce_iommu_map(vcpu->kvm,
> +						stit->tbl, entry + i, gpa,
> +						iommu_tce_direction(tce));
> +					if (ret != H_SUCCESS)
> +						goto unlock_exit;
> +				}

Um.. what value will this for_each leave in stit after completion?  I
suspect it will be something bogus, which means re-using stit in the
next 0..npages loop iteration won't be safe (you only initialize stit
with the first entry outside that loop).

> +			}
> +		}
> +
>  		kvmppc_tce_put(stt, entry + i, tce);
>  	}
>  
> @@ -307,6 +602,7 @@ 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)
> @@ -320,6 +616,25 @@ long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
>  	if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
>  		return H_PARAMETER;
>  
> +	stit = list_first_entry_or_null(&stt->iommu_tables,
> +			struct kvmppc_spapr_tce_iommu_table, next);
> +	if (stit) {
> +		if (iommu_tce_clear_param_check(stit->tbl, ioba,
> +					tce_value, npages))
> +			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)
> +					return ret;

Again do you need some sort of cleanup for partial completion?

> +			}
> +		}
> +	}
> +
>  	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 dc1c66fda941..018c7d94a575 100644
> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
> @@ -178,11 +178,104 @@ 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 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)
> +		return H_HARDWARE;
> +
> +	pua = (void *) vmalloc_to_phys(pua);
> +	if (!pua)
> +		return H_TOO_HARD;
> +
> +	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))
> +		return H_HARDWARE;
> +
> +	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;
> +}
> +
> +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_PARAMETER;
> +
> +	mem = mm_iommu_lookup_rm(vcpu->kvm->mm, ua, 1ULL << tbl->it_page_shift);
> +	if (!mem)
> +		return H_TOO_HARD;
> +
> +	if (mm_iommu_ua_to_hpa_rm(mem, ua, &hpa))
> +		return H_HARDWARE;
> +
> +	pua = (void *) vmalloc_to_phys(pua);
> +	if (!pua)
> +		return H_HARDWARE;

What circumstances can this fail under?  Does it need to be H_TOO_HARD instead?

> +
> +	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->kvm, tbl, entry);
> +
> +	*pua = ua;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(kvmppc_rm_tce_iommu_map);
> +
>  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, gpa;
> +	enum dma_data_direction dir;
>  
>  	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
>  	/* 	    liobn, ioba, tce); */
> @@ -199,6 +292,33 @@ long kvmppc_rm_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>  	if (ret != H_SUCCESS)
>  		return ret;
>  
> +	stit = list_first_entry_or_null(&stt->iommu_tables,
> +			struct kvmppc_spapr_tce_iommu_table, next);
> +	if (stit) {
> +		entry = ioba >> stit->tbl->it_page_shift;
> +		gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +		dir = iommu_tce_direction(tce);
> +
> +		if (dir == DMA_NONE) {
> +			if (iommu_tce_clear_param_check(stit->tbl, ioba, 0, 1))
> +				return H_PARAMETER;
> +		} else {
> +			if (iommu_tce_put_param_check(stit->tbl, ioba, gpa))
> +				return H_PARAMETER;
> +		}
> +
> +		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, stit->tbl,
> +						entry, gpa, dir);
> +			if (ret != H_SUCCESS)
> +				return ret;
> +		}
> +	}
> +
>  	kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
>  
>  	return H_SUCCESS;
> @@ -237,9 +357,10 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  {
>  	struct kvmppc_spapr_tce_table *stt;
>  	long i, ret = H_SUCCESS;
> -	unsigned long tces, entry, tce, ua = 0;
> +	unsigned long tces, entry, gpa, tce, 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)
> @@ -303,17 +424,45 @@ long kvmppc_rm_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>  		}
>  	}
>  
> +	stit = list_first_entry_or_null(&stt->iommu_tables,
> +			struct kvmppc_spapr_tce_iommu_table, next);
> +
>  	for (i = 0; i < npages; ++i) {
>  		tce = be64_to_cpu(((u64 *)tces)[i]);
>  
>  		ret = kvmppc_tce_validate(stt, tce);
>  		if (ret != H_SUCCESS)
>  			goto unlock_exit;
> +
> +		if (stit) {
> +			gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +			ret = iommu_tce_put_param_check(stit->tbl,
> +					ioba + (i << stit->tbl->it_page_shift),
> +					gpa);
> +			if (ret != H_SUCCESS)
> +				goto unlock_exit;
> +
> +		}
>  	}
>  
>  	for (i = 0; i < npages; ++i) {
>  		tce = be64_to_cpu(((u64 *)tces)[i]);

As noted in the earlier patch this is really dangerous - by reloading
the tce from userspace you've thrown away the verification above.

> +		if (stit) {
> +			for (i = 0; i < npages; ++i) {
> +				gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
> +
> +				list_for_each_entry_lockless(stit,
> +						&stt->iommu_tables, next) {
> +					ret = kvmppc_rm_tce_iommu_map(vcpu,
> +						stit->tbl, entry + i, gpa,
> +						iommu_tce_direction(tce));
> +					if (ret != H_SUCCESS)
> +						goto unlock_exit;
> +				}
> +			}
> +		}
> +
>  		kvmppc_tce_put(stt, entry + i, tce);
>  	}
>  
> @@ -330,6 +479,8 @@ 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)
> @@ -343,6 +494,25 @@ long kvmppc_rm_h_stuff_tce(struct kvm_vcpu *vcpu,
>  	if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
>  		return H_PARAMETER;
>  
> +	stit = list_first_entry_or_null(&stt->iommu_tables,
> +			struct kvmppc_spapr_tce_iommu_table, next);
> +	if (stit) {
> +		if (iommu_tce_clear_param_check(stit->tbl, ioba,
> +					tce_value, npages))
> +			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)
> +					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 cd892dec7cb6..f3127dc87912 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 */

I'm not sure why this one should get a fallthrough comment, when none
of the other cases do.

> +	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);
> +

Is there any particular reason you unwrap the group fd here, but the
table fd inside kvm__spapr_tce_attach_iommu_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 */
>  	}
>  
>  	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