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

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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 <aik@xxxxxxxxx>
>> ---
>> 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.



> 
>> +{
>> +	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.
> 
>> +	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".


> 
>> +
>> +	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.



> 
>> +	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.


> 
>> +	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.


> 
>> +	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.



>>  
>>  	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);
> 


-- 
Alexey

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