[PATCH kernel 6/9] KVM: PPC: Associate IOMMU group with guest view of TCE table
David Gibson
david at gibson.dropbear.id.au
Tue Mar 8 15:55:08 AEDT 2016
On Mon, Mar 07, 2016 at 08:38:13PM +1100, Alexey Kardashevskiy wrote:
> On 03/07/2016 05:25 PM, David Gibson wrote:
> >On Mon, Mar 07, 2016 at 02:41:14PM +1100, Alexey Kardashevskiy wrote:
> >>The existing in-kernel TCE table for emulated devices contains
> >>guest physical addresses which are accesses by emulated devices.
> >>Since we need to keep this information for VFIO devices too
> >>in order to implement H_GET_TCE, we are reusing it.
> >>
> >>This adds IOMMU group list to kvmppc_spapr_tce_table. Each group
> >>will have an iommu_table pointer.
> >>
> >>This adds kvm_spapr_tce_attach_iommu_group() helper and its detach
> >>counterpart to manage the lists.
> >>
> >>This puts a group when:
> >>- guest copy of TCE table is destroyed when TCE table fd is closed;
> >>- kvm_spapr_tce_detach_iommu_group() is called from
> >>the KVM_DEV_VFIO_GROUP_DEL ioctl handler in the case vfio-pci hotunplug
> >>(will be added in the following patch).
> >>
> >>Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> >>---
> >> arch/powerpc/include/asm/kvm_host.h | 8 +++
> >> arch/powerpc/include/asm/kvm_ppc.h | 6 ++
> >> arch/powerpc/kvm/book3s_64_vio.c | 108 ++++++++++++++++++++++++++++++++++++
> >> 3 files changed, 122 insertions(+)
> >>
> >>diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> >>index 2e7c791..2c5c823 100644
> >>--- a/arch/powerpc/include/asm/kvm_host.h
> >>+++ b/arch/powerpc/include/asm/kvm_host.h
> >>@@ -178,6 +178,13 @@ struct kvmppc_pginfo {
> >> atomic_t refcnt;
> >> };
> >>
> >>+struct kvmppc_spapr_tce_group {
> >>+ struct list_head next;
> >>+ struct rcu_head rcu;
> >>+ struct iommu_group *refgrp;/* for reference counting only */
> >>+ struct iommu_table *tbl;
> >>+};
> >>+
> >> struct kvmppc_spapr_tce_table {
> >> struct list_head list;
> >> struct kvm *kvm;
> >>@@ -186,6 +193,7 @@ struct kvmppc_spapr_tce_table {
> >> u32 page_shift;
> >> u64 offset; /* in pages */
> >> u64 size; /* window size in pages */
> >>+ struct list_head groups;
> >> struct page *pages[0];
> >> };
> >>
> >>diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> >>index 2544eda..d1482dc 100644
> >>--- a/arch/powerpc/include/asm/kvm_ppc.h
> >>+++ b/arch/powerpc/include/asm/kvm_ppc.h
> >>@@ -164,6 +164,12 @@ 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,
> >>+ unsigned long liobn,
> >>+ phys_addr_t start_addr,
> >>+ struct iommu_group *grp);
> >>+extern void kvm_spapr_tce_detach_iommu_group(struct kvm *kvm,
> >>+ struct iommu_group *grp);
> >> extern long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> >> struct kvm_create_spapr_tce_64 *args);
> >> extern struct kvmppc_spapr_tce_table *kvmppc_find_table(
> >>diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
> >>index 2c2d103..846d16d 100644
> >>--- a/arch/powerpc/kvm/book3s_64_vio.c
> >>+++ b/arch/powerpc/kvm/book3s_64_vio.c
> >>@@ -27,6 +27,7 @@
> >> #include <linux/hugetlb.h>
> >> #include <linux/list.h>
> >> #include <linux/anon_inodes.h>
> >>+#include <linux/iommu.h>
> >>
> >> #include <asm/tlbflush.h>
> >> #include <asm/kvm_ppc.h>
> >>@@ -95,10 +96,18 @@ static void release_spapr_tce_table(struct rcu_head *head)
> >> struct kvmppc_spapr_tce_table *stt = container_of(head,
> >> struct kvmppc_spapr_tce_table, rcu);
> >> unsigned long i, npages = kvmppc_tce_pages(stt->size);
> >>+ struct kvmppc_spapr_tce_group *kg;
> >>
> >> for (i = 0; i < npages; i++)
> >> __free_page(stt->pages[i]);
> >>
> >>+ while (!list_empty(&stt->groups)) {
> >>+ kg = list_first_entry(&stt->groups,
> >>+ struct kvmppc_spapr_tce_group, next);
> >>+ list_del(&kg->next);
> >>+ kfree(kg);
> >>+ }
> >>+
> >> kfree(stt);
> >> }
> >>
> >>@@ -129,9 +138,15 @@ static int kvm_spapr_tce_mmap(struct file *file, struct vm_area_struct *vma)
> >> static int kvm_spapr_tce_release(struct inode *inode, struct file *filp)
> >> {
> >> struct kvmppc_spapr_tce_table *stt = filp->private_data;
> >>+ struct kvmppc_spapr_tce_group *kg;
> >>
> >> list_del_rcu(&stt->list);
> >>
> >>+ list_for_each_entry_rcu(kg, &stt->groups, next) {
> >>+ iommu_group_put(kg->refgrp);
> >>+ kg->refgrp = NULL;
> >>+ }
> >
> >What's the reason for this kind of two-phase deletion? Dereffing the
> >group here, and setting to NULL, then actually removing from the liast above.
>
> Well, this way I have only one RCU-delayed release_spapr_tce_table(). The
> other option would be to call for each @kg:
> - list_del(&kg->next);
> - call_rcu()
>
> as release_spapr_tce_table() won't be able to delete them - they are not in
> the list anymore.
Ah, ok, that makes sense.
> I suppose I can reuse kvm_spapr_tce_put_group(), this looks inaccurate...
>
>
>
> >
> >> kvm_put_kvm(stt->kvm);
> >>
> >> kvmppc_account_memlimit(
> >>@@ -146,6 +161,98 @@ static const struct file_operations kvm_spapr_tce_fops = {
> >> .release = kvm_spapr_tce_release,
> >> };
> >>
> >>+extern long kvm_spapr_tce_attach_iommu_group(struct kvm *kvm,
> >>+ unsigned long liobn,
> >>+ phys_addr_t start_addr,
> >>+ struct iommu_group *grp)
> >>+{
> >>+ struct kvmppc_spapr_tce_table *stt = NULL;
> >>+ struct iommu_table_group *table_group;
> >>+ long i;
> >>+ bool found = false;
> >>+ struct kvmppc_spapr_tce_group *kg;
> >>+ struct iommu_table *tbltmp;
> >>+
> >>+ /* Check this LIOBN hasn't been previously allocated */
> >
> >This comment does not appear to be correct.
> >
> >>+ list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list) {
> >>+ if (stt->liobn == liobn) {
> >>+ if ((stt->offset << stt->page_shift) != start_addr)
> >>+ return -EINVAL;
> >>+
> >>+ found = true;
> >>+ break;
> >>+ }
> >>+ }
> >>+
> >>+ if (!found)
> >>+ return -ENODEV;
> >>+
> >>+ /* Find IOMMU group and table at @start_addr */
> >>+ table_group = iommu_group_get_iommudata(grp);
> >>+ if (!table_group)
> >>+ return -EFAULT;
> >>+
> >>+ tbltmp = NULL;
> >>+ for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
> >>+ struct iommu_table *tbl = table_group->tables[i];
> >>+
> >>+ if (!tbl)
> >>+ continue;
> >>+
> >>+ if ((tbl->it_page_shift == stt->page_shift) &&
> >>+ (tbl->it_offset == stt->offset)) {
> >>+ tbltmp = tbl;
> >>+ break;
> >>+ }
> >>+ }
> >>+ if (!tbltmp)
> >>+ return -ENODEV;
> >>+
> >>+ list_for_each_entry_rcu(kg, &stt->groups, next) {
> >>+ if (kg->refgrp == grp)
> >>+ return -EBUSY;
> >>+ }
> >>+
> >>+ kg = kzalloc(sizeof(*kg), GFP_KERNEL);
> >>+ kg->refgrp = grp;
> >>+ kg->tbl = tbltmp;
> >>+ list_add_rcu(&kg->next, &stt->groups);
> >>+
> >>+ return 0;
> >>+}
> >>+
> >>+static void kvm_spapr_tce_put_group(struct rcu_head *head)
> >>+{
> >>+ struct kvmppc_spapr_tce_group *kg = container_of(head,
> >>+ struct kvmppc_spapr_tce_group, rcu);
> >>+
> >>+ iommu_group_put(kg->refgrp);
> >>+ kg->refgrp = NULL;
> >>+ kfree(kg);
> >>+}
> >>+
> >>+extern void kvm_spapr_tce_detach_iommu_group(struct kvm *kvm,
> >>+ struct iommu_group *grp)
> >
> >Hrm. attach takes an explicit liobn, but this one iterates over all
> >liobns. Why the asymmetry?
>
>
> For attach(), LIOBN is specified in an additional (to VFIO KVM device's "add
> group") ioctl(). There is no need for "detach" ioctl() as we only want this
> detach() to happen when a group is removed from a container, and in this
> case the usual KVM_DEV_VFIO_GROUP_DEL is good enough hint that we need to
> detach LIOBN. Since _DEL does not take LIOBN, here I have a loop.
>
> I'll put this in the commit log next time.
>
>
> >
> >>+{
> >>+ struct kvmppc_spapr_tce_table *stt;
> >>+ struct iommu_table_group *table_group;
> >>+ struct kvmppc_spapr_tce_group *kg;
> >>+
> >>+ table_group = iommu_group_get_iommudata(grp);
> >>+ if (!table_group)
> >>+ return;
> >>+
> >>+ list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list) {
> >>+ list_for_each_entry_rcu(kg, &stt->groups, next) {
> >>+ if (kg->refgrp == grp) {
> >>+ list_del_rcu(&kg->next);
> >>+ call_rcu(&kg->rcu, kvm_spapr_tce_put_group);
> >>+ break;
> >>+ }
> >>+ }
> >>+ }
> >>+}
> >>+
> >> long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> >> struct kvm_create_spapr_tce_64 *args)
> >> {
> >>@@ -181,6 +288,7 @@ 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->groups);
> >>
> >> for (i = 0; i < npages; i++) {
> >> stt->pages[i] = alloc_page(GFP_KERNEL | __GFP_ZERO);
> >
>
>
--
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
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