[PATCH kernel 9/9] KVM: PPC: VFIO device: support SPAPR TCE
Alexey Kardashevskiy
aik at ozlabs.ru
Wed Mar 9 20:20:12 AEDT 2016
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.
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;
>> }
>>
>
--
Alexey
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