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

From: Alexey Kardashevskiy <[email-masked]>
Date: Sat, 05 Oct 2013 11:52:16 +1000

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.
> 
>>  #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.

-- 
With best regards

Alexey Kardashevskiy -- icq: 52150396