Subject: Re: [PATCH kernel 4/4] KVM: PPC: Add support for 64bit TCE windows

From: David Gibson <[email-masked]>
Date: Mon, 25 Jan 2016 16:37:27 +1100

On Thu, Jan 21, 2016 at 07:15:26PM +1100, Alexey Kardashevskiy wrote:
> The existing KVM_CREATE_SPAPR_TCE only supports 32bit windows which is not
> enough for directly mapped windows as the guest can get more than 4GB.
> 
> This adds KVM_CREATE_SPAPR_TCE_64 ioctl and advertises it
> via KVM_CAP_SPAPR_TCE_64 capability.
> 
> Since 64bit windows are to support Dynamic DMA windows (DDW), let's add
> @bus_offset and @page_shift which are also required by DDW.
> 
> Signed-off-by: Alexey Kardashevskiy <[email-masked]>
> ---
>  Documentation/virtual/kvm/api.txt   | 32 ++++++++++++++++++++++++++++++++
>  arch/powerpc/include/asm/kvm_ppc.h  |  2 +-
>  arch/powerpc/include/uapi/asm/kvm.h |  9 +++++++++
>  arch/powerpc/kvm/book3s_64_vio.c    | 10 +++++++---
>  arch/powerpc/kvm/powerpc.c          | 25 ++++++++++++++++++++++++-
>  include/uapi/linux/kvm.h            |  2 ++
>  6 files changed, 75 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index da39435..d1c5655 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3060,6 +3060,38 @@ an implementation for these despite the in kernel acceleration.
>  
>  This capability is always enabled.
>  
> +4.96 KVM_CREATE_SPAPR_TCE_64
> +
> +Capability: KVM_CAP_SPAPR_TCE_64
> +Architectures: powerpc
> +Type: vm ioctl
> +Parameters: struct kvm_create_spapr_tce_64 (in)
> +Returns: file descriptor for manipulating the created TCE table
> +
> +This is an extension for KVM_CAP_SPAPR_TCE which only supports 32bit
> +windows, described in 4.62 KVM_CREATE_SPAPR_TCE
> +
> +This capability uses extended struct in ioctl interface:
> +
> +/* for KVM_CAP_SPAPR_TCE_64 */
> +struct kvm_create_spapr_tce_64 {
> +	__u64 liobn;
> +	__u32 page_shift;
> +	__u64 offset;	/* in pages */
> +	__u64 size; 	/* in pages */
> +	__u32 flags;

Best to move page_shift after offset and size, so the structure
doesn't get an alignment gap.

> +};
> +
> +The aim of extension is to support an additional bigger DMA window with
> +a variable page size.
> +KVM_CREATE_SPAPR_TCE_64 receives a 64bit window size, an IOMMU page shift and
> +a bus offset of the corresponding DMA window, @size and @offset are numbers
> +of IOMMU pages.
> +
> +@flags are not used at the moment.
> +
> +The rest of functionality is identical to KVM_CREATE_SPAPR_TCE.
> +
>  5. The kvm_run structure
>  ------------------------
>  
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index 4cadee5..6e4d1dc 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -165,7 +165,7 @@ extern void kvmppc_map_vrma(struct kvm_vcpu *vcpu,
>  extern int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu);
>  
>  extern long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> -				struct kvm_create_spapr_tce *args);
> +				struct kvm_create_spapr_tce_64 *args);
>  extern struct kvmppc_spapr_tce_table *kvmppc_find_table(
>  		struct kvm_vcpu *vcpu, unsigned long liobn);
>  extern long kvmppc_ioba_validate(struct kvmppc_spapr_tce_table *stt,
> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> index ab4d473..9c8b4cbc 100644
> --- a/arch/powerpc/include/uapi/asm/kvm.h
> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> @@ -333,6 +333,15 @@ struct kvm_create_spapr_tce {
>  	__u32 window_size;
>  };
>  
> +/* for KVM_CAP_SPAPR_TCE_64 */
> +struct kvm_create_spapr_tce_64 {
> +	__u64 liobn;
> +	__u32 page_shift;
> +	__u64 offset;	/* in pages */
> +	__u64 size;	/* in pages */
> +	__u32 flags;
> +};
> +
>  /* for KVM_ALLOCATE_RMA */
>  struct kvm_allocate_rma {
>  	__u64 rma_size;
> diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
> index 85ee572..5479446 100644
> --- a/arch/powerpc/kvm/book3s_64_vio.c
> +++ b/arch/powerpc/kvm/book3s_64_vio.c
> @@ -144,20 +144,23 @@ static const struct file_operations kvm_spapr_tce_fops = {
>  };
>  
>  long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
> -				   struct kvm_create_spapr_tce *args)
> +				   struct kvm_create_spapr_tce_64 *args)
>  {
>  	struct kvmppc_spapr_tce_table *stt = NULL;
>  	unsigned long npages, size;
>  	int ret = -ENOMEM;
>  	int i;
>  
> +	if (!args->size)
> +		return -EINVAL;
> +
>  	/* Check this LIOBN hasn't been previously allocated */
>  	list_for_each_entry(stt, &kvm->arch.spapr_tce_tables, list) {
>  		if (stt->liobn == args->liobn)
>  			return -EBUSY;
>  	}
>  
> -	size = args->window_size >> IOMMU_PAGE_SHIFT_4K;
> +	size = args->size;

Doesn't this need some kind of bounds on the allowed size?

>  	npages = kvmppc_stt_npages(size);
>  	ret = kvmppc_account_memlimit(npages, true);
>  	if (ret) {
> @@ -171,7 +174,8 @@ long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
>  		goto fail;
>  
>  	stt->liobn = args->liobn;
> -	stt->page_shift = IOMMU_PAGE_SHIFT_4K;
> +	stt->page_shift = args->page_shift;
> +	stt->offset = args->offset;
>  	stt->size = size;
>  	stt->kvm = kvm;
>  
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 164735c..2b0fe92 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -33,6 +33,7 @@
>  #include <asm/tlbflush.h>
>  #include <asm/cputhreads.h>
>  #include <asm/irqflags.h>
> +#include <asm/iommu.h>
>  #include "timing.h"
>  #include "irq.h"
>  #include "../mm/mmu_decl.h"
> @@ -509,6 +510,7 @@ 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_PPC_ALLOC_HTAB:
>  	case KVM_CAP_PPC_RTAS:
>  	case KVM_CAP_PPC_FIXUP_HCALL:
> @@ -1334,13 +1336,34 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  		break;
>  	}
>  #ifdef CONFIG_PPC_BOOK3S_64
> +	case KVM_CREATE_SPAPR_TCE_64: {
> +		struct kvm_create_spapr_tce_64 create_tce_64;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&create_tce_64, argp, sizeof(create_tce_64)))
> +			goto out;
> +		if (create_tce_64.flags) {
> +			r = -EINVAL;
> +			goto out;
> +		}
> +		r = kvm_vm_ioctl_create_spapr_tce(kvm, &create_tce_64);
> +		goto out;
> +	}
>  	case KVM_CREATE_SPAPR_TCE: {
>  		struct kvm_create_spapr_tce create_tce;
> +		struct kvm_create_spapr_tce_64 create_tce_64;
>  
>  		r = -EFAULT;
>  		if (copy_from_user(&create_tce, argp, sizeof(create_tce)))
>  			goto out;
> -		r = kvm_vm_ioctl_create_spapr_tce(kvm, &create_tce);
> +
> +		create_tce_64.liobn = create_tce.liobn;
> +		create_tce_64.page_shift = IOMMU_PAGE_SHIFT_4K;
> +		create_tce_64.offset = 0;
> +		create_tce_64.size = create_tce.window_size >>
> +				IOMMU_PAGE_SHIFT_4K;
> +		create_tce_64.flags = 0;
> +		r = kvm_vm_ioctl_create_spapr_tce(kvm, &create_tce_64);
>  		goto out;
>  	}
>  	case KVM_PPC_GET_SMMU_INFO: {
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8ce5f64..b06208b 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1143,6 +1143,8 @@ struct kvm_s390_ucas_mapping {
>  /* Available with KVM_CAP_PPC_ALLOC_HTAB */
>  #define KVM_PPC_ALLOCATE_HTAB	  _IOWR(KVMIO, 0xa7, __u32)
>  #define KVM_CREATE_SPAPR_TCE	  _IOW(KVMIO,  0xa8, struct kvm_create_spapr_tce)
> +#define KVM_CREATE_SPAPR_TCE_64	  _IOW(KVMIO,  0xa8, \
> +				       struct kvm_create_spapr_tce_64)
>  /* Available with KVM_CAP_RMA */
>  #define KVM_ALLOCATE_RMA	  _IOR(KVMIO,  0xa9, struct kvm_allocate_rma)
>  /* Available with KVM_CAP_PPC_HTAB_FD */

-- 
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