[PATCH kernel 9/9] KVM: PPC: VFIO device: support SPAPR TCE
David Gibson
david at gibson.dropbear.id.au
Thu Mar 10 16:21:08 AEDT 2016
On Wed, Mar 09, 2016 at 08:20:12PM +1100, Alexey Kardashevskiy wrote:
> On 03/09/2016 04:45 PM, David Gibson wrote:
> >On Mon, Mar 07, 2016 at 02:41:17PM +1100, Alexey Kardashevskiy wrote:
> >>sPAPR TCE IOMMU is para-virtualized and the guest does map/unmap
> >>via hypercalls which take a logical bus id (LIOBN) as a target IOMMU
> >>identifier. LIOBNs are made up, advertised to guest systems and
> >>linked to IOMMU groups by the user space.
> >>In order to enable acceleration for IOMMU operations in KVM, we need
> >>to tell KVM the information about the LIOBN-to-group mapping.
> >>
> >>For that, a new KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE_LIOBN parameter
> >>is added which accepts:
> >>- a VFIO group fd and IO base address to find the actual hardware
> >>TCE table;
> >>- a LIOBN to assign to the found table.
> >>
> >>Before notifying KVM about new link, this check the group for being
> >>registered with KVM device in order to release them at unexpected KVM
> >>finish.
> >>
> >>This advertises the new KVM_CAP_SPAPR_TCE_VFIO capability to the user
> >>space.
> >>
> >>While we are here, this also fixes VFIO KVM device compiling to let it
> >>link to a KVM module.
> >>
> >>Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> >>---
> >> Documentation/virtual/kvm/devices/vfio.txt | 21 +++++-
> >> arch/powerpc/kvm/Kconfig | 1 +
> >> arch/powerpc/kvm/Makefile | 5 +-
> >> arch/powerpc/kvm/powerpc.c | 1 +
> >> include/uapi/linux/kvm.h | 9 +++
> >> virt/kvm/vfio.c | 106 +++++++++++++++++++++++++++++
> >> 6 files changed, 140 insertions(+), 3 deletions(-)
> >>
> >>diff --git a/Documentation/virtual/kvm/devices/vfio.txt b/Documentation/virtual/kvm/devices/vfio.txt
> >>index ef51740..c0d3eb7 100644
> >>--- a/Documentation/virtual/kvm/devices/vfio.txt
> >>+++ b/Documentation/virtual/kvm/devices/vfio.txt
> >>@@ -16,7 +16,24 @@ 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.
> >
> >AFAICT these changes are accurate for VFIO as it is already, in which
> >case it might be clearer to put them in a separate patch.
> >
> >> 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.
> >>
> >>-For each, kvm_device_attr.addr points to an int32_t file descriptor
> >>-for the VFIO group.
> >>+ KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE_LIOBN: sets a liobn for a VFIO group
> >>+ kvm_device_attr.addr points to a struct:
> >>+ struct kvm_vfio_spapr_tce_liobn {
> >>+ __u32 argsz;
> >>+ __s32 fd;
> >>+ __u32 liobn;
> >>+ __u8 pad[4];
> >>+ __u64 start_addr;
> >>+ };
> >>+ where
> >>+ @argsz is the size of kvm_vfio_spapr_tce_liobn;
> >>+ @fd is a file descriptor for a VFIO group;
> >>+ @liobn is a logical bus id to be associated with the group;
> >>+ @start_addr is a DMA window offset on the IO (PCI) bus
> >
> >For the cause of DDW and multiple windows, I'm assuming you can call
> >this multiple times with different LIOBNs and the same IOMMU group?
>
>
> Yes. It is called twice per each group (when DDW is activated) - for 32bit
> and 64bit windows, this is why @start_addr is there.
>
>
> >>diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
> >>index 1059846..dfa3488 100644
> >>--- a/arch/powerpc/kvm/Kconfig
> >>+++ b/arch/powerpc/kvm/Kconfig
> >>@@ -65,6 +65,7 @@ config KVM_BOOK3S_64
> >> select KVM
> >> select KVM_BOOK3S_PR_POSSIBLE if !KVM_BOOK3S_HV_POSSIBLE
> >> select SPAPR_TCE_IOMMU if IOMMU_SUPPORT
> >>+ select KVM_VFIO if VFIO
> >> ---help---
> >> Support running unmodified book3s_64 and book3s_32 guest kernels
> >> in virtual machines on book3s_64 host processors.
> >>diff --git a/arch/powerpc/kvm/Makefile b/arch/powerpc/kvm/Makefile
> >>index 7f7b6d8..71f577c 100644
> >>--- a/arch/powerpc/kvm/Makefile
> >>+++ b/arch/powerpc/kvm/Makefile
> >>@@ -8,7 +8,7 @@ ccflags-y := -Ivirt/kvm -Iarch/powerpc/kvm
> >> KVM := ../../../virt/kvm
> >>
> >> common-objs-y = $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o \
> >>- $(KVM)/eventfd.o $(KVM)/vfio.o
> >>+ $(KVM)/eventfd.o
> >
> >Please don't disable the VFIO device for the non-book3s case. I added
> >it (even though it didn't do anything until now) so that libvirt
> >wouldn't choke when it finds it's not available. Obviously the new
> >ioctl needs to be only for the right IOMMU setup, but the device
> >itself should be available always.
>
> Ah. Ok, I'll fix this. I just wanted to be able to compile kvm as a module.
>
>
> >> CFLAGS_e500_mmu.o := -I.
> >> CFLAGS_e500_mmu_host.o := -I.
> >>@@ -87,6 +87,9 @@ endif
> >> kvm-book3s_64-objs-$(CONFIG_KVM_XICS) += \
> >> book3s_xics.o
> >>
> >>+kvm-book3s_64-objs-$(CONFIG_KVM_VFIO) += \
> >>+ $(KVM)/vfio.o \
> >>+
> >> kvm-book3s_64-module-objs += \
> >> $(KVM)/kvm_main.o \
> >> $(KVM)/eventfd.o \
> >>diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> >>index 19aa59b..63f188d 100644
> >>--- a/arch/powerpc/kvm/powerpc.c
> >>+++ b/arch/powerpc/kvm/powerpc.c
> >>@@ -521,6 +521,7 @@ 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:
> >>+ 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/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> >>index 080ffbf..f1abbea 100644
> >>--- a/include/uapi/linux/kvm.h
> >>+++ b/include/uapi/linux/kvm.h
> >>@@ -1056,6 +1056,7 @@ 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_LIOBN 3
> >>
> >> enum kvm_device_type {
> >> KVM_DEV_TYPE_FSL_MPIC_20 = 1,
> >>@@ -1075,6 +1076,14 @@ enum kvm_device_type {
> >> KVM_DEV_TYPE_MAX,
> >> };
> >>
> >>+struct kvm_vfio_spapr_tce_liobn {
> >>+ __u32 argsz;
> >>+ __s32 fd;
> >>+ __u32 liobn;
> >>+ __u8 pad[4];
> >>+ __u64 start_addr;
> >>+};
> >>+
> >> /*
> >> * ioctls for VM fds
> >> */
> >>diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> >>index 1dd087d..87c771e 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;
> >>@@ -60,6 +64,22 @@ static void kvm_vfio_group_put_external_user(struct vfio_group *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;
> >
> >Should this be -ESOMETHING?
> >
> >>+ 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 bool kvm_vfio_group_is_coherent(struct vfio_group *vfio_group)
> >> {
> >> long (*fn)(struct vfio_group *, unsigned long);
> >>@@ -110,6 +130,22 @@ static void kvm_vfio_update_coherency(struct kvm_device *dev)
> >> mutex_unlock(&kv->lock);
> >> }
> >>
> >>+#ifdef CONFIG_SPAPR_TCE_IOMMU
> >>+static void kvm_vfio_spapr_detach_iommu_group(struct kvm *kvm,
> >>+ struct vfio_group *vfio_group)
> >
> >
> >Shouldn't this go in the same patch that introduced the attach
> >function?
>
> Having less patches which touch different maintainers areas is better. I
> cannot avoid touching both PPC KVM and VFIO in this patch but I can in
> "[PATCH kernel 6/9] KVM: PPC: Associate IOMMU group with guest view of TCE
> table".
>
>
> >
> >>+{
> >>+ int group_id;
> >>+ struct iommu_group *grp;
> >>+
> >>+ group_id = kvm_vfio_external_user_iommu_id(vfio_group);
> >>+ grp = iommu_group_get_by_id(group_id);
> >>+ if (grp) {
> >>+ kvm_spapr_tce_detach_iommu_group(kvm, grp);
> >>+ iommu_group_put(grp);
> >>+ }
> >>+}
> >>+#endif
> >>+
> >> static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
> >> {
> >> struct kvm_vfio *kv = dev->private;
> >>@@ -186,6 +222,10 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
> >> continue;
> >>
> >> list_del(&kvg->node);
> >>+#ifdef CONFIG_SPAPR_TCE_IOMMU
> >
> >Better to make a no-op version of the call than have to #ifdef at the
> >callsite.
>
> It is questionable. A x86 reader may decide that
> KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE_LIOBN is implemented for x86 and get
> confused.
>
>
> >
> >>+ kvm_vfio_spapr_detach_iommu_group(dev->kvm,
> >>+ kvg->vfio_group);
> >>+#endif
> >> kvm_vfio_group_put_external_user(kvg->vfio_group);
> >> kfree(kvg);
> >> ret = 0;
> >>@@ -201,6 +241,69 @@ 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_LIOBN: {
> >>+ struct kvm_vfio_spapr_tce_liobn 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_liobn,
> >>+ start_addr);
> >>+
> >>+ if (copy_from_user(¶m, (void __user *)arg, minsz))
> >>+ return -EFAULT;
> >>+
> >>+ if (param.argsz < minsz)
> >>+ return -EINVAL;
> >>+
> >>+ f = fdget(param.fd);
> >>+ 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;
> >
> >Shouldn't there be some runtime test for the type of the IOMMU? It's
> >possible a kernel could be built for a platform supporting multiple
> >IOMMU types.
>
> Well, may make sense but I do not know to test that. The IOMMU type is a
> VFIO container property, not a group property and here (KVM) we only have
> groups.
Which, as mentioned previously, is broken.
> And calling iommu_group_get_iommudata() is quite useless as it returns a
> void pointer... I could probably check that the release() callback is the
> one I set via iommu_group_set_iommudata() but there is no API to get it from
> a group.
>
> And I cannot really imagine a kernel with CONFIG_PPC_BOOK3S_64 (and
> therefore KVM_CAP_SPAPR_TCE_VFIO enabled) with different IOMMU types. Can
> the same kernel binary image work on both BOOK3S and embedded PPC? Where
> these other types can come from?
>
>
> >
> >>+ 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.liobn, param.start_addr,
> >>+ grp);
> >>+ if (ret)
> >>+ iommu_group_put(grp);
> >>+ break;
> >>+ }
> >>+
> >>+ mutex_unlock(&kv->lock);
> >>+
> >>+ kvm_vfio_group_put_external_user(vfio_group);
> >>+
> >>+ return ret;
> >>+ }
> >>+#endif /* CONFIG_SPAPR_TCE_IOMMU */
> >> }
> >>
> >> return -ENXIO;
> >>@@ -225,6 +328,9 @@ 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_LIOBN:
> >>+#endif
> >> return 0;
> >> }
> >>
> >
>
>
--
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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