Subject: Re: [RFC PATCH] PPC: KVM: vfio kvm device: support spapr tce

From: Alexey Kardashevskiy <[email-masked]>
Date: Sat, 05 Oct 2013 13:36:46 +1000

On 10/05/2013 11:52 AM, Alexey Kardashevskiy wrote:
> On 05.10.2013 2:05, Alex Williamson wrote:
>> On Fri, 2013-10-04 at 22:24 +1000, Alexey Kardashevskiy wrote:
>>> This is a very rough change set required for ppc64 to use this KVM device.
>>>
>>> vfio_rm.c is a piece of code which is going to be called from the realmode (MMU off),
>>> and I will put everything spapr-related under #ifdef CONFIG_SPAPR_TCE_IOMMU,
>>> it is just friday and I have to run :)
>>>
>>> This is an RFC but it works.
>>>
>>> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
>>> ---
>>>  arch/powerpc/kvm/Kconfig  |  1 +
>>>  arch/powerpc/kvm/Makefile |  4 ++++
>>>  include/linux/kvm_host.h  |  8 ++++---
>>>  include/linux/vfio.h      |  3 +++
>>>  include/uapi/linux/kvm.h  |  1 +
>>>  virt/kvm/vfio.c           | 46 ++++++++++++++++++++++++++++++++++++++++
>>>  virt/kvm/vfio_rm.c        | 54 +++++++++++++++++++++++++++++++++++++++++++++++
>>>  7 files changed, 114 insertions(+), 3 deletions(-)
>>>  create mode 100644 virt/kvm/vfio_rm.c
>>>
>>> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
>>> index 61b3535..d1b7f64 100644
>>> --- a/arch/powerpc/kvm/Kconfig
>>> +++ b/arch/powerpc/kvm/Kconfig
>>> @@ -60,6 +60,7 @@ config KVM_BOOK3S_64
>>>  	select KVM_BOOK3S_64_HANDLER
>>>  	select KVM
>>>  	select SPAPR_TCE_IOMMU
>>> +	select KVM_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 6646c95..fc2878b 100644
>>> --- a/arch/powerpc/kvm/Makefile
>>> +++ b/arch/powerpc/kvm/Makefile
>>> @@ -55,6 +55,8 @@ kvm-objs-$(CONFIG_KVM_E500MC) := $(kvm-e500mc-objs)
>>>  
>>>  kvm-book3s_64-objs-$(CONFIG_KVM_BOOK3S_64_PR) := \
>>>  	$(KVM)/coalesced_mmio.o \
>>> +	$(KVM)/vfio.o \
>>> +	$(KVM)/vfio_rm.o \
>>>  	fpu.o \
>>>  	book3s_paired_singles.o \
>>>  	book3s_pr.o \
>>> @@ -76,6 +78,7 @@ kvm-book3s_64-objs-$(CONFIG_KVM_BOOK3S_64_HV) := \
>>>  kvm-book3s_64-builtin-xics-objs-$(CONFIG_KVM_XICS) := \
>>>  	book3s_hv_rm_xics.o
>>>  kvm-book3s_64-builtin-objs-$(CONFIG_KVM_BOOK3S_64_HV) := \
>>> +	$(KVM)/vfio_rm.o \
>>>  	book3s_hv_rmhandlers.o \
>>>  	book3s_hv_rm_mmu.o \
>>>  	book3s_64_vio_hv.o \
>>> @@ -89,6 +92,7 @@ kvm-book3s_64-objs-$(CONFIG_KVM_XICS) += \
>>>  
>>>  kvm-book3s_64-module-objs := \
>>>  	$(KVM)/kvm_main.o \
>>> +	$(KVM)/vfio.o \
>>>  	$(KVM)/eventfd.o \
>>>  	powerpc.o \
>>>  	emulate.o \
>>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>>> index ad2b581..43c0290 100644
>>> --- a/include/linux/kvm_host.h
>>> +++ b/include/linux/kvm_host.h
>>> @@ -407,6 +407,8 @@ struct kvm {
>>>  #endif
>>>  	long tlbs_dirty;
>>>  	struct list_head devices;
>>> +
>>> +	struct kvm_vfio *vfio;
>>
>>
>> <cringe> can't this be on kvm->arch?
> 
> It can, I just thought since it is valid for more than just one
> platform, it can go here.
> 
> 
>>>  };
>>>  
>>>  #define kvm_err(fmt, ...) \
>>> @@ -677,15 +679,15 @@ void kvm_arch_register_noncoherent_dma(struct kvm *kvm);
>>>  void kvm_arch_unregister_noncoherent_dma(struct kvm *kvm);
>>>  bool kvm_arch_has_noncoherent_dma(struct kvm *kvm);
>>>  #else
>>> -static inline void kvm_arch_register_noncoherent_dma(void)
>>> +static inline void kvm_arch_register_noncoherent_dma(struct kvm *kvm)
>>>  {
>>>  }
>>>  
>>> -static inline void kvm_arch_unregister_noncoherent_dma(void)
>>> +static inline void kvm_arch_unregister_noncoherent_dma(struct kvm *kvm)
>>>  {
>>>  }
>>>  
>>> -static inline bool kvm_arch_has_noncoherent_dma(void)
>>> +static inline bool kvm_arch_has_noncoherent_dma(struct kvm *kvm)
>>>  {
>>>  	return false;
>>>  }
>>
>> Will fix in my series.
>>
>>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>>> index 24579a0..681e19b 100644
>>> --- a/include/linux/vfio.h
>>> +++ b/include/linux/vfio.h
>>> @@ -97,4 +97,7 @@ extern struct vfio_group *vfio_group_get_external_user(struct file *filep);
>>>  extern void vfio_group_put_external_user(struct vfio_group *group);
>>>  extern int vfio_external_user_iommu_id(struct vfio_group *group);
>>>  
>>> +extern struct iommu_group *vfio_find_group_by_liobn(struct kvm *kvm,
>>> +		unsigned long liobn);
>>> +
>>
>> Wrong header file.

btw there are two - uapi/linux/vfio.h and linux/vfio.h. The external user
API is in linux/vfio.h but my change should go to uapi/linux/vfio.h, is
that correct? Or we need a third header? Just asking, no kidding, no arguing :)

>>
>>>  #endif /* VFIO_H */
>>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>>> index 7c1a349..a74ad16 100644
>>> --- a/include/uapi/linux/kvm.h
>>> +++ b/include/uapi/linux/kvm.h
>>> @@ -847,6 +847,7 @@ 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_SPAPR_TCE_LIOBN		2
>>>  
>>>  /*
>>>   * ioctls for VM fds
>>> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
>>> index 2e336a7..39dea9f 100644
>>> --- a/virt/kvm/vfio.c
>>> +++ b/virt/kvm/vfio.c
>>> @@ -22,6 +22,7 @@
>>>  struct kvm_vfio_group {
>>>  	struct list_head node;
>>>  	struct vfio_group *vfio_group;
>>> +	uint64_t liobn; /* sPAPR */
>>
>> Perhaps an arch pointer or at least a union.
>>
>>>  };
>>>  
>>>  struct kvm_vfio {
>>> @@ -188,12 +189,52 @@ static int kvm_vfio_set_group(struct kvm_device *dev, long attr, u64 arg)
>>>  	return -ENXIO;
>>>  }
>>>  
>>> +static int kvm_vfio_set_spapr_tce_liobn(struct kvm_device *dev,
>>> +		long attr, u64 arg)
>>> +{
>>> +	struct kvm_vfio *kv = dev->private;
>>> +	struct vfio_group *vfio_group;
>>> +	struct kvm_vfio_group *kvg;
>>> +	void __user *argp = (void __user *)arg;
>>> +	struct fd f;
>>> +	int32_t fd;
>>> +	uint64_t liobn = attr;
>>> +
>>> +	if (get_user(fd, (int32_t __user *)argp))
>>> +		return -EFAULT;
>>> +
>>> +	f = fdget(fd);
>>> +	if (!f.file)
>>> +		return -EBADF;
>>> +
>>> +	vfio_group = kvm_vfio_group_get_external_user(f.file);
>>> +	fdput(f);
>>> +
>>> +	list_for_each_entry(kvg, &kv->group_list, node) {
>>> +		if (kvg->vfio_group == vfio_group) {
>>> +			WARN_ON(kvg->liobn);
>>
>> Users shouldn't be able to trigger WARN_ON so easily, return -EBUSY,
>> allow it to be unset and re-set, or just allow the overwrite.
>>
>>> +			kvg->liobn = liobn;
>>> +			kvm_vfio_group_put_external_user(vfio_group);
>>> +			return 0;
>>> +		}
>>> +	}
>>> +
>>> +	kvm_vfio_group_put_external_user(vfio_group);
>>> +
>>> +	return -ENXIO;
>>> +}
>>> +
>>>  static int kvm_vfio_set_attr(struct kvm_device *dev,
>>>  			     struct kvm_device_attr *attr)
>>>  {
>>>  	switch (attr->group) {
>>>  	case KVM_DEV_VFIO_GROUP:
>>>  		return kvm_vfio_set_group(dev, attr->attr, attr->addr);
>>> +#ifdef CONFIG_SPAPR_TCE_IOMMU
>>> +	case KVM_DEV_VFIO_SPAPR_TCE_LIOBN:
>>> +		return kvm_vfio_set_spapr_tce_liobn(dev, attr->attr,
>>> +				attr->addr);
>>> +#endif
>>>  	}
>>>  
>>>  	return -ENXIO;
>>> @@ -211,6 +252,10 @@ static int kvm_vfio_has_attr(struct kvm_device *dev,
>>>  		}
>>>  
>>>  		break;
>>> +#ifdef CONFIG_SPAPR_TCE_IOMMU
>>> +	case KVM_DEV_VFIO_SPAPR_TCE_LIOBN:
>>> +		return 0;
>>> +#endif
>>>  	}
>>>  
>>>  	return -ENXIO;
>>> @@ -250,6 +295,7 @@ static int kvm_vfio_create(struct kvm_device *dev, u32 type)
>>>  	mutex_init(&kv->lock);
>>>  
>>>  	dev->private = kv;
>>> +	dev->kvm->vfio = kv;
>>>  
>>>  	return 0;
>>>  }
>>> diff --git a/virt/kvm/vfio_rm.c b/virt/kvm/vfio_rm.c
>>> new file mode 100644
>>> index 0000000..ee9fd96
>>> --- /dev/null
>>> +++ b/virt/kvm/vfio_rm.c
>>> @@ -0,0 +1,54 @@
>>> +#include <linux/errno.h>
>>> +#include <linux/file.h>
>>> +#include <linux/kvm_host.h>
>>> +#include <linux/list.h>
>>> +#include <linux/module.h>
>>> +#include <linux/mutex.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/uaccess.h>
>>> +#include <linux/vfio.h>
>>> +
>>> +struct kvm_vfio_group {
>>> +	struct list_head node;
>>> +	struct vfio_group *vfio_group;
>>> +	uint64_t liobn; /* sPAPR */
>>> +};
>>> +
>>> +struct kvm_vfio {
>>> +	struct list_head group_list;
>>> +	struct mutex lock;
>>> +	bool noncoherent;
>>> +};
>>> +
>>> +struct vfio_group {
>>> +	struct kref			kref;
>>> +	int				minor;
>>> +	atomic_t			container_users;
>>> +	struct iommu_group		*iommu_group;
>>> +	struct vfio_container		*container;
>>> +	struct list_head		device_list;
>>> +	struct mutex			device_lock;
>>> +	struct device			*dev;
>>> +	struct notifier_block		nb;
>>> +	struct list_head		vfio_next;
>>> +	struct list_head		container_next;
>>> +	atomic_t			opened;
>>> +};
>>> +
>>> +struct iommu_group *vfio_find_group_by_liobn(struct kvm *kvm, unsigned long liobn)
>>> +{
>>> +	struct kvm_vfio_group *kvg;
>>> +
>>> +	if (!kvm->vfio)
>>> +		return NULL;
>>> +
>>> +	list_for_each_entry(kvg, &kvm->vfio->group_list, node) {
>>> +		if (kvg->liobn == liobn)
>>> +			return kvg->vfio_group->iommu_group;
>>> +	}
>>> +
>>> +	return NULL;
>>> +}
>>> +EXPORT_SYMBOL_GPL(vfio_find_group_by_liobn);
>>> +
>>> +
>>
>> You're kidding, right?  These are intentionally private data structures
>> that are blatantly copied so that you can extract what you want.  NACK.
>> The iommu_group is available off struct device, do you even need vfio or
>> this kvm-vfio device to get from liobn to iommu_group?  Thanks,
> 
> 
> This is an RFC. I am not saying this is what can go to upstream or
> anything. I am not kidding (why everyone assumes that?), I am showing
> what API I would like to have in the VFIO KVM device. I need the way to
> get iommu_table (which is in a private data of iommu_group) by LIOBN and
> the VFIO KVM device is the _only_ entity which will know about this
> connection (LIOBN is made up by the qemu and told to the guest) and it
> cannot go to the kvm.ko - and the patch like this is the best way to
> show it as my english obviously sucks.

Oh. I was confused by:
drivers/vfio/vfio.c|67| struct vfio_group {
drivers/vfio/vfio_iommu_type1.c|73| struct vfio_group {

which are two completely different types (confusing).

So. I either need an additional file to compile to the kernel for mmu-off
case (such as vfio_rm.c) and share vfio_group struct via some internal
header or compile vfio.c into the kernel image always, in this case I'll
need to export kvm_vfio_ops symbol. What would you suggest?

-- 
Alexey