[PATCH kernel v6 10/10] KVM: PPC: VFIO: Add in-kernel acceleration for VFIO
Alexey Kardashevskiy
aik at ozlabs.ru
Mon Mar 6 16:04:55 AEDT 2017
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!
--
Alexey
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