[PATCH kernel v6 10/10] KVM: PPC: VFIO: Add in-kernel acceleration for VFIO
Alexey Kardashevskiy
aik at ozlabs.ru
Tue Mar 7 22:07:27 AEDT 2017
On 06/03/17 16:04, Alexey Kardashevskiy wrote:
> On 06/03/17 15:30, David Gibson wrote:
>> On Fri, Mar 03, 2017 at 06:09:25PM +1100, Alexey Kardashevskiy wrote:
>>> On 03/03/17 16:59, David Gibson wrote:
>>>> On Thu, Mar 02, 2017 at 07:56:44PM +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.
>>>>>
>>>>> If we fail to update a hardware IOMMU table unexpected reason, we just
>>>>> clear it and move on as there is nothing really we can do about it -
>>>>> for example, if we hot plug a VFIO device to a guest, existing TCE tables
>>>>> will be mirrored automatically to the hardware and there is no interface
>>>>> to report to the guest about possible failures.
>>>>>
>>>>> This adds new attribute - KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE - to
>>>>> the VFIO KVM device. It takes a VFIO group fd and SPAPR TCE table fd
>>>>> and associates a physical IOMMU table with the SPAPR TCE table (which
>>>>> is a guest view of the hardware IOMMU table). The iommu_table object
>>>>> is cached and referenced so we do not have to look up for it in real mode.
>>>>>
>>>>> This does not implement the UNSET counterpart as there is no use for it -
>>>>> once the acceleration is enabled, the existing userspace won't
>>>>> disable it unless a VFIO container is destroyed; this adds necessary
>>>>> cleanup to the KVM_DEV_VFIO_GROUP_DEL handler.
>>>>>
>>>>> As this creates a descriptor per IOMMU table-LIOBN couple (called
>>>>> kvmppc_spapr_tce_iommu_table), it is possible to have several
>>>>> descriptors with the same iommu_table (hardware IOMMU table) attached
>>>>> to the same LIOBN; we do not remove duplicates though as
>>>>> iommu_table_ops::exchange not just update a TCE entry (which is
>>>>> shared among IOMMU groups) but also invalidates the TCE cache
>>>>> (one per IOMMU group).
>>>>>
>>>>> This advertises the new KVM_CAP_SPAPR_TCE_VFIO capability to the user
>>>>> space.
>>>>>
>>>>> This 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 at ozlabs.ru>
>>>>> ---
>>>>> Changes:
>>>>> v6:
>>>>> * changed handling of errors returned by kvmppc_(rm_)tce_iommu_(un)map()
>>>>> * moved kvmppc_gpa_to_ua() to TCE validation
>>>>>
>>>>> v5:
>>>>> * changed error codes in multiple places
>>>>> * added bunch of WARN_ON() in places which should not really happen
>>>>> * adde a check that an iommu table is not attached already to LIOBN
>>>>> * dropped explicit calls to iommu_tce_clear_param_check/
>>>>> iommu_tce_put_param_check as kvmppc_tce_validate/kvmppc_ioba_validate
>>>>> call them anyway (since the previous patch)
>>>>> * if we fail to update a hardware IOMMU table for unexpected reason,
>>>>> this just clears the entry
>>>>>
>>>>> v4:
>>>>> * added note to the commit log about allowing multiple updates of
>>>>> the same IOMMU table;
>>>>> * instead of checking for if any memory was preregistered, this
>>>>> returns H_TOO_HARD if a specific page was not;
>>>>> * fixed comments from v3 about error handling in many places;
>>>>> * simplified TCE handlers and merged IOMMU parts inline - for example,
>>>>> there used to be kvmppc_h_put_tce_iommu(), now it is merged into
>>>>> kvmppc_h_put_tce(); this allows to check IOBA boundaries against
>>>>> the first attached table only (makes the code simpler);
>>>>>
>>>>> v3:
>>>>> * simplified not to use VFIO group notifiers
>>>>> * reworked cleanup, should be cleaner/simpler now
>>>>>
>>>>> v2:
>>>>> * reworked to use new VFIO notifiers
>>>>> * now same iommu_table may appear in the list several times, to be fixed later
>>>>> ---
>>>>> Documentation/virtual/kvm/devices/vfio.txt | 22 +-
>>>>> arch/powerpc/include/asm/kvm_host.h | 8 +
>>>>> arch/powerpc/include/asm/kvm_ppc.h | 4 +
>>>>> include/uapi/linux/kvm.h | 8 +
>>>>> arch/powerpc/kvm/book3s_64_vio.c | 321 ++++++++++++++++++++++++++++-
>>>>> arch/powerpc/kvm/book3s_64_vio_hv.c | 165 ++++++++++++++-
>>>>> arch/powerpc/kvm/powerpc.c | 2 +
>>>>> virt/kvm/vfio.c | 60 ++++++
>>>>> 8 files changed, 585 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 7bba8f415627..857ae2c6aa39 100644
>>>>> --- a/arch/powerpc/include/asm/kvm_host.h
>>>>> +++ b/arch/powerpc/include/asm/kvm_host.h
>>>>> @@ -191,6 +191,13 @@ struct kvmppc_pginfo {
>>>>> atomic_t refcnt;
>>>>> };
>>>>>
>>>>> +struct kvmppc_spapr_tce_iommu_table {
>>>>> + struct rcu_head rcu;
>>>>> + struct list_head next;
>>>>> + struct vfio_group *group;
>>>>> + struct iommu_table *tbl;
>>>>> +};
>>>>> +
>>>>> struct kvmppc_spapr_tce_table {
>>>>> struct list_head list;
>>>>> struct kvm *kvm;
>>>>> @@ -199,6 +206,7 @@ struct kvmppc_spapr_tce_table {
>>>>> u32 page_shift;
>>>>> u64 offset; /* in pages */
>>>>> u64 size; /* window size in pages */
>>>>> + struct list_head iommu_tables;
>>>>> struct page *pages[0];
>>>>> };
>>>>>
>>>>> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
>>>>> index 72c2a155641f..66de7e73b3d3 100644
>>>>> --- a/arch/powerpc/include/asm/kvm_ppc.h
>>>>> +++ b/arch/powerpc/include/asm/kvm_ppc.h
>>>>> @@ -164,6 +164,10 @@ extern long kvmppc_prepare_vrma(struct kvm *kvm,
>>>>> extern void kvmppc_map_vrma(struct kvm_vcpu *vcpu,
>>>>> struct kvm_memory_slot *memslot, unsigned long porder);
>>>>> extern int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu);
>>>>> +extern long kvm_spapr_tce_attach_iommu_group(struct kvm *kvm, int tablefd,
>>>>> + struct vfio_group *group);
>>>>> +extern void kvm_spapr_tce_release_iommu_group(struct kvm *kvm,
>>>>> + struct vfio_group *group);
>>>>>
>>>>> extern long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
>>>>> struct kvm_create_spapr_tce_64 *args);
>>>>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>>>>> index f5a52ffb6b58..e743cb0d176e 100644
>>>>> --- a/include/uapi/linux/kvm.h
>>>>> +++ b/include/uapi/linux/kvm.h
>>>>> @@ -1088,6 +1088,7 @@ struct kvm_device_attr {
>>>>> #define KVM_DEV_VFIO_GROUP 1
>>>>> #define KVM_DEV_VFIO_GROUP_ADD 1
>>>>> #define KVM_DEV_VFIO_GROUP_DEL 2
>>>>> +#define KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE 3
>>>>>
>>>>> enum kvm_device_type {
>>>>> KVM_DEV_TYPE_FSL_MPIC_20 = 1,
>>>>> @@ -1109,6 +1110,13 @@ enum kvm_device_type {
>>>>> KVM_DEV_TYPE_MAX,
>>>>> };
>>>>>
>>>>> +struct kvm_vfio_spapr_tce {
>>>>> + __u32 argsz;
>>>>> + __u32 flags;
>>>>> + __s32 groupfd;
>>>>> + __s32 tablefd;
>>>>> +};
>>>>> +
>>>>> /*
>>>>> * ioctls for VM fds
>>>>> */
>>>>> diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
>>>>> index 57dd036bd998..85927f467811 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 +124,130 @@ static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
>>>>> return ret;
>>>>> }
>>>>>
>>>>> +static void kvm_spapr_tce_iommu_table_free(struct rcu_head *head)
>>>>> +{
>>>>> + struct kvmppc_spapr_tce_iommu_table *stit = container_of(head,
>>>>> + struct kvmppc_spapr_tce_iommu_table, rcu);
>>>>> +
>>>>> + iommu_table_put(stit->tbl);
>>>>> + kvm_vfio_group_put_external_user(stit->group);
>>>>> +
>>>>> + kfree(stit);
>>>>> +}
>>>>> +
>>>>> +static void kvm_spapr_tce_liobn_release_iommu_group(
>>>>> + struct kvmppc_spapr_tce_table *stt,
>>>>> + struct vfio_group *group)
>>>>> +{
>>>>> + struct kvmppc_spapr_tce_iommu_table *stit, *tmp;
>>>>> +
>>>>> + list_for_each_entry_safe(stit, tmp, &stt->iommu_tables, next) {
>>>>> + if (group && (stit->group != group))
>>>>> + continue;
>>>>> +
>>>>> + list_del_rcu(&stit->next);
>>>>> +
>>>>> + call_rcu(&stit->rcu, kvm_spapr_tce_iommu_table_free);
>>>>> + }
>>>>> +}
>>>>> +
>>>>> +extern void kvm_spapr_tce_release_iommu_group(struct kvm *kvm,
>>>>> + struct vfio_group *group)
>>>>> +{
>>>>> + struct kvmppc_spapr_tce_table *stt;
>>>>> +
>>>>> + list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list)
>>>>> + kvm_spapr_tce_liobn_release_iommu_group(stt, group);
>>>>> +}
>>>>> +
>>>>> +extern long kvm_spapr_tce_attach_iommu_group(struct kvm *kvm, int tablefd,
>>>>> + struct vfio_group *group)
>>>>> +{
>>>>> + struct kvmppc_spapr_tce_table *stt = NULL;
>>>>> + bool found = false;
>>>>> + struct iommu_table *tbl = NULL;
>>>>> + struct iommu_table_group *table_group;
>>>>> + long i, ret = 0;
>>>>> + struct kvmppc_spapr_tce_iommu_table *stit;
>>>>> + struct fd f;
>>>>> + int group_id;
>>>>> + struct iommu_group *grp;
>>>>> +
>>>>> + group_id = kvm_vfio_external_user_iommu_id(group);
>>>>> + grp = iommu_group_get_by_id(group_id);
>>>>> + if (WARN_ON(!grp))
>>>>> + return -EIO;
>>>>> +
>>>>> + f = fdget(tablefd);
>>>>> + if (!f.file) {
>>>>> + ret = -EBADF;
>>>>> + goto put_exit;
>>>>> + }
>>>>> +
>>>>> + list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list) {
>>>>> + if (stt == f.file->private_data) {
>>>>> + found = true;
>>>>> + break;
>>>>> + }
>>>>> + }
>>>>> +
>>>>> + fdput(f);
>>>>> +
>>>>> + if (!found) {
>>>>> + ret = -EINVAL;
>>>>> + goto put_exit;
>>>>> + }
>>>>> +
>>>>> + table_group = iommu_group_get_iommudata(grp);
>>>>> + if (WARN_ON(!table_group)) {
>>>>> + ret = -EFAULT;
>>>>> + goto put_exit;
>>>>> + }
>>>>> +
>>>>> + for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
>>>>> + struct iommu_table *tbltmp = table_group->tables[i];
>>>>> +
>>>>> + if (!tbltmp)
>>>>> + continue;
>>>>> +
>>>>> + /*
>>>>> + * Make sure hardware table parameters are exactly the same;
>>>>> + * this is used in the TCE handlers where boundary checks
>>>>> + * use only the first attached table.
>>>>> + */
>>>>> + if ((tbltmp->it_page_shift == stt->page_shift) &&
>>>>> + (tbltmp->it_offset == stt->offset) &&
>>>>> + (tbltmp->it_size == stt->size)) {
>>>>> + tbl = tbltmp;
>>>>> + break;
>>>>> + }
>>>>> + }
>>>>> + if (!tbl) {
>>>>> + ret = -EINVAL;
>>>>> + goto put_exit;
>>>>> + }
>>>>> +
>>>>> + list_for_each_entry_rcu(stit, &stt->iommu_tables, next) {
>>>>> + if ((stit->tbl == tbl) && (stit->group == group)) {
>>>>> + ret = -EBUSY;
>>>>> + goto put_exit;
>>>>> + }
>>>>> + }
>>>>> +
>>>>> + iommu_table_get(tbl);
>>>>> +
>>>>> + stit = kzalloc(sizeof(*stit), GFP_KERNEL);
>>>>> + stit->tbl = tbl;
>>>>> + stit->group = group;
>>>>> +
>>>>> + list_add_rcu(&stit->next, &stt->iommu_tables);
>>>>> +
>>>>> +put_exit:
>>>>> + iommu_group_put(grp);
>>>>> +
>>>>> + return ret;
>>>>> +}
>>>>> +
>>>>> static void release_spapr_tce_table(struct rcu_head *head)
>>>>> {
>>>>> struct kvmppc_spapr_tce_table *stt = container_of(head,
>>>>> @@ -132,6 +290,8 @@ 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(
>>>>> @@ -182,6 +342,7 @@ 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);
>>>>> @@ -210,11 +371,99 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
>>>>> return ret;
>>>>> }
>>>>>
>>>>> +static void kvmppc_clear_tce(struct iommu_table *tbl, unsigned long entry)
>>>>> +{
>>>>> + unsigned long hpa = 0;
>>>>> + enum dma_data_direction dir = DMA_NONE;
>>>>> +
>>>>> + iommu_tce_xchg(tbl, entry, &hpa, &dir);
>>>>> +}
>>>>> +
>>>>> +static long kvmppc_tce_iommu_mapped_dec(struct kvm *kvm,
>>>>> + struct iommu_table *tbl, unsigned long entry)
>>>>> +{
>>>>> + struct mm_iommu_table_group_mem_t *mem = NULL;
>>>>> + const unsigned long pgsize = 1ULL << tbl->it_page_shift;
>>>>> + unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
>>>>> +
>>>>> + if (WARN_ON_ONCE(!pua))
>>>>> + return H_HARDWARE;
>>>>> +
>>>>> + 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 ua,
>>>>> + enum dma_data_direction dir)
>>>>> +{
>>>>> + long ret;
>>>>> + unsigned long hpa, *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
>>>>> + struct mm_iommu_table_group_mem_t *mem;
>>>>> +
>>>>> + if (!pua)
>>>>> + /* it_userspace allocation might be delayed */
>>>>> + return H_TOO_HARD;
>>>>> +
>>>>> + mem = mm_iommu_lookup(kvm->mm, ua, 1ULL << tbl->it_page_shift);
>>>>> + if (!mem)
>>>>> + return H_TOO_HARD;
>>>>
>>>> IIUC this is the virtual mode path, not the real mode patch. Under
>>>> what circumstances could qemu succeed that KVM virtual mode couldn't,
>>>> for either of the above failures?
>>>
>>> The (!pua) failure is handled in tce_iommu_build_v2() from
>>> drivers/vfio/vfio_iommu_spapr_tce.c as:
>>>
>>>
>>> if (!tbl->it_userspace) {
>>> ret = tce_iommu_userspace_view_alloc(tbl, container->mm);
>>> if (ret)
>>> return ret;
>>> }
>>
>> Ah.. which is called from the ioctl() path but not the KVM hcall path,
>> ok, I get it.
>>
>>> The (!mem) can succeed if the container is in VFIO_SPAPR_TCE_IOMMU mode
>>> (not VFIO_SPAPR_TCE_v2_IOMMU). Remember that the userspace can call
>>> ioctl(vfio_kvm_device, KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE) without having
>>> memory preregistered so tables will appear in the
>>> kvmppc_spapr_tce_iommu_table list in KVM.
>>
>> Ok. So in short, the userspace->ioctl() path will handle both v1 and
>> v2 versions of the IOMMU interface, whereas the in-kernel
>> implementation (both real and virtual) will only handle v2. Is that
>> right?
>
>
> Correct. I used to have an explicit check for any memory preregistered, now
> it is as bit less obvious but still the case.
>
>
>
>
>>
>>>>> +
>>>>> + if (WARN_ON_ONCE(mm_iommu_ua_to_hpa(mem, ua, &hpa)))
>>>>> + return H_HARDWARE;
>>>>> +
>>>>> + if (mm_iommu_mapped_inc(mem))
>>>>> + return H_CLOSED;
>>>>> +
>>>>> + ret = iommu_tce_xchg(tbl, entry, &hpa, &dir);
>>>>> + if (ret) {
>>>>
>>>> It thought the xchg could basically never fail, so this should be
>>>> another WARN_ON().
>>>
>>>
>>> Correct.
>>>
>>>
>>>>> + 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, ua = 0;
>>>>> + enum dma_data_direction dir;
>>>>>
>>>>> /* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
>>>>> /* liobn, ioba, tce); */
>>>>> @@ -231,7 +480,35 @@ long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
>>>>> if (ret != H_SUCCESS)
>>>>> return ret;
>>>>>
>>>>> - kvmppc_tce_put(stt, ioba >> stt->page_shift, tce);
>>>>> + dir = iommu_tce_direction(tce);
>>>>> + if ((dir != DMA_NONE) && kvmppc_gpa_to_ua(vcpu->kvm,
>>>>> + tce & ~(TCE_PCI_READ | TCE_PCI_WRITE), &ua, NULL))
>>>>> + return H_PARAMETER;
>>>>> +
>>>>> + entry = ioba >> stt->page_shift;
>>>>> +
>>>>> + list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
>>>>> + if (dir == DMA_NONE) {
>>>>> + ret = kvmppc_tce_iommu_unmap(vcpu->kvm,
>>>>> + stit->tbl, entry);
>>>>> + } else {
>>>>> + idx = srcu_read_lock(&vcpu->kvm->srcu);
>>>>> + ret = kvmppc_tce_iommu_map(vcpu->kvm, stit->tbl,
>>>>> + entry, ua, dir);
>>>>> + srcu_read_unlock(&vcpu->kvm->srcu, idx);
>>>>> + }
>>>>> +
>>>>> + if (ret == H_SUCCESS)
>>>>> + continue;
>>>>> +
>>>>> + if (ret == H_TOO_HARD)
>>>>> + return ret;
>>>>> +
>>>>> + WARN_ON_ONCE(1);
>>>>> + kvmppc_clear_tce(stit->tbl, entry);
>>>>> + }
>>>>> +
>>>>> + kvmppc_tce_put(stt, entry, tce);
>>>>>
>>>>> return H_SUCCESS;
>>>>> }
>>>>> @@ -246,6 +523,7 @@ 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)
>>>>> @@ -284,6 +562,26 @@ long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
>>>>> if (ret != H_SUCCESS)
>>>>> goto unlock_exit;
>>>>>
>>>>> + if (kvmppc_gpa_to_ua(vcpu->kvm,
>>>>> + tce & ~(TCE_PCI_READ | TCE_PCI_WRITE),
>>>>> + &ua, NULL))
>>>>> + return H_PARAMETER;
>>>>> +
>>>>> + list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
>>>>> + ret = kvmppc_tce_iommu_map(vcpu->kvm,
>>>>> + stit->tbl, entry + i, ua,
>>>>> + iommu_tce_direction(tce));
>>>>> +
>>>>> + if (ret == H_SUCCESS)
>>>>> + continue;
>>>>> +
>>>>> + if (ret == H_TOO_HARD)
>>>>> + goto unlock_exit;
>>>>> +
>>>>> + WARN_ON_ONCE(1);
>>>>> + kvmppc_clear_tce(stit->tbl, entry);
>>>>> + }
>>>>> +
>>>>> kvmppc_tce_put(stt, entry + i, tce);
>>>>> }
>>>>>
>>>>> @@ -300,6 +598,7 @@ 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)
>>>>> @@ -313,6 +612,24 @@ long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
>>>>> if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
>>>>> return H_PARAMETER;
>>>>>
>>>>> + list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
>>>>> + unsigned long entry = ioba >> stit->tbl->it_page_shift;
>>>>> +
>>>>> + for (i = 0; i < npages; ++i) {
>>>>> + ret = kvmppc_tce_iommu_unmap(vcpu->kvm,
>>>>> + stit->tbl, entry + i);
>>>>> +
>>>>> + if (ret == H_SUCCESS)
>>>>> + continue;
>>>>> +
>>>>> + if (ret == H_TOO_HARD)
>>>>> + return ret;
>>>>> +
>>>>> + WARN_ON_ONCE(1);
>>>>> + kvmppc_clear_tce(stit->tbl, entry);
>>>>> + }
>>>>> + }
>>>>> +
>>>>> for (i = 0; i < npages; ++i, ioba += (1ULL << stt->page_shift))
>>>>> kvmppc_tce_put(stt, ioba >> stt->page_shift, tce_value);
>>>>>
>>>>> diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c b/arch/powerpc/kvm/book3s_64_vio_hv.c
>>>>> index 440d3ab5dc32..3ad06badc552 100644
>>>>> --- a/arch/powerpc/kvm/book3s_64_vio_hv.c
>>>>> +++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
>>>>> @@ -161,11 +161,108 @@ long kvmppc_gpa_to_ua(struct kvm *kvm, unsigned long gpa,
>>>>> EXPORT_SYMBOL_GPL(kvmppc_gpa_to_ua);
>>>>>
>>>>> #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
>>>>> +static void kvmppc_rm_clear_tce(struct iommu_table *tbl, unsigned long entry)
>>>>> +{
>>>>> + unsigned long hpa = 0;
>>>>> + enum dma_data_direction dir = DMA_NONE;
>>>>> +
>>>>> + iommu_tce_xchg_rm(tbl, entry, &hpa, &dir);
>>>>> +}
>>>>> +
>>>>> +static long kvmppc_rm_tce_iommu_mapped_dec(struct kvm *kvm,
>>>>> + struct iommu_table *tbl, unsigned long entry)
>>>>> +{
>>>>> + struct mm_iommu_table_group_mem_t *mem = NULL;
>>>>> + const unsigned long pgsize = 1ULL << tbl->it_page_shift;
>>>>> + unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
>>>>> +
>>>>> + if (WARN_ON_ONCE(!pua))
>>>>> + return H_HARDWARE;
>>>>
>>>> So.. I know I encouraged WARN_ON()s, but is it safe to call WARN_ON()
>>>> from real mode?
>>>
>>> Ouch. Tried WARN_ON_ONCE(1) in kvmppc_rm_h_stuff_tce() and got "rcu_sched
>>> detected stalls" straight away.
>>
>> Bother. Sorry I didn't think of that earlier.
>>
>>> What do I replace it with, in documenting purposes?
>>>
>>> - if (WARN_ON_ONCE(!pua))
>>> + if (!pua) /* Not expected to fail */
>>
>> So, I'd suggest adding a WARN_ON_RM() or whatever macro to wrap this
>> at least. As you may have seen I discussed this with mpe on IRC and
>> printk() should work, so you could just put a printk() and
>> dump_stack() in there.
>
> Yes, noticed. Thanks!
>
Something like this? Copied from include/asm-generic/bug.h.
diff --git a/arch/powerpc/kvm/book3s_64_vio_hv.c
b/arch/powerpc/kvm/book3s_64_vio_hv.c
index 3ad06badc552..9d6f7e2043ca 100644
--- a/arch/powerpc/kvm/book3s_64_vio_hv.c
+++ b/arch/powerpc/kvm/book3s_64_vio_hv.c
@@ -40,6 +40,31 @@
#include <asm/iommu.h>
#include <asm/tce.h>
+#ifdef CONFIG_BUG
+
+#define WARN_ON_ONCE_RM(condition) ({ \
+ static bool __section(.data.unlikely) __warned; \
+ int __ret_warn_once = !!(condition); \
+ \
+ if (unlikely(__ret_warn_once && !__warned)) { \
+ __warned = true; \
+ pr_err("WARN_ON_ONCE_RM: (%s) at %s:%u\n", \
+ __stringify(condition), \
+ __func__, __LINE__); \
+ dump_stack(); \
+ } \
+ unlikely(__ret_warn_once); \
+})
+
+#else
+
+#define WARN_ON_ONCE_RM(condition) ({ \
+ int __ret_warn_on = !!(condition); \
+ unlikely(__ret_warn_on); \
+})
+
+#endif
+
>
>
>
--
Alexey
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 839 bytes
Desc: OpenPGP digital signature
URL: <http://lists.ozlabs.org/pipermail/linuxppc-dev/attachments/20170307/6b9f076a/attachment-0001.sig>
More information about the Linuxppc-dev
mailing list