Re: [Qemu-ppc] [PATCH qemu] target-ppc: kvm: make use of KVM_CREATE_SPAPR_TCE_64

[David Gibson]

On Thu, Dec 22, 2016 at 12:13:12PM +1100, Alexey Kardashevskiy wrote:
> KVM_CAP_SPAPR_TCE capability allows creating TCE tables in KVM which
> allows having in-kernel acceleration for H_PUT_TCE_xxx hypercalls.
> However it only supports 32bit DMA windows at zero bus offset.
> 
> There is a new KVM_CAP_SPAPR_TCE_64 capability which supports 64bit
> window size, variable page size and bus offset.
> 
> This makes use of the new capability. The kernel headers are already
> updated as the kernel support went in to v4.6.
> 
> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> ---
>  target-ppc/kvm_ppc.h | 12 +++++++-----
>  hw/ppc/spapr_iommu.c |  8 +++++---
>  target-ppc/kvm.c     | 48 +++++++++++++++++++++++++++++++++++++-----------
>  3 files changed, 49 insertions(+), 19 deletions(-)
> 
> diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
> index bd1d78bfbe..14320c2378 100644
> --- a/target-ppc/kvm_ppc.h
> +++ b/target-ppc/kvm_ppc.h
> @@ -36,8 +36,9 @@ int kvmppc_booke_watchdog_enable(PowerPCCPU *cpu);
>  #ifndef CONFIG_USER_ONLY
>  off_t kvmppc_alloc_rma(void **rma);
>  bool kvmppc_spapr_use_multitce(void);
> -void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t window_size, int *pfd,
> -                              bool need_vfio);
> +void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t page_shift,
> +                              uint64_t bus_offset, uint32_t nb_table,
> +                              int *pfd, bool need_vfio);
>  int kvmppc_remove_spapr_tce(void *table, int pfd, uint32_t window_size);
>  int kvmppc_reset_htab(int shift_hint);
>  uint64_t kvmppc_rma_size(uint64_t current_size, unsigned int hash_shift);
> @@ -168,9 +169,10 @@ static inline bool kvmppc_spapr_use_multitce(void)
>      return false;
>  }
>  
> -static inline void *kvmppc_create_spapr_tce(uint32_t liobn,
> -                                            uint32_t window_size, int *fd,
> -                                            bool need_vfio)
> +static inline void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t 
> page_shift,
> +                                            uint64_t bus_offset,
> +                                            uint32_t nb_table,
> +                                            int *pfd, bool need_vfio)
>  {
>      return NULL;
>  }
> diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
> index ae30bbe30f..29c80bb3c8 100644
> --- a/hw/ppc/spapr_iommu.c
> +++ b/hw/ppc/spapr_iommu.c
> @@ -79,15 +79,16 @@ static IOMMUAccessFlags 
> spapr_tce_iommu_access_flags(uint64_t tce)
>  
>  static uint64_t *spapr_tce_alloc_table(uint32_t liobn,
>                                         uint32_t page_shift,
> +                                       uint64_t bus_offset,
>                                         uint32_t nb_table,
>                                         int *fd,
>                                         bool need_vfio)
>  {
>      uint64_t *table = NULL;
> -    uint64_t window_size = (uint64_t)nb_table << page_shift;
>  
> -    if (kvm_enabled() && !(window_size >> 32)) {
> -        table = kvmppc_create_spapr_tce(liobn, window_size, fd, need_vfio);
> +    if (kvm_enabled()) {

This is broken.  Previously, if we had a >4GiB window, we'd fall back
to managing it in userspace, which would work, albeit slowly.  Now, if
you have an older kernel which doesn't support KVM_CAP_SPAPR_TCE_64 it
will attempt to allocate it in the kernel, and fail completely.

> +        table = kvmppc_create_spapr_tce(liobn, page_shift, bus_offset, 
> nb_table,
> +                                        fd, need_vfio);
>      }
>  
>      if (!table) {
> @@ -342,6 +343,7 @@ void spapr_tce_table_enable(sPAPRTCETable *tcet,
>      tcet->nb_table = nb_table;
>      tcet->table = spapr_tce_alloc_table(tcet->liobn,
>                                          tcet->page_shift,
> +                                        tcet->bus_offset,
>                                          tcet->nb_table,
>                                          &tcet->fd,
>                                          tcet->need_vfio);
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index 9c4834c4fc..6e91a4d8bb 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -71,6 +71,7 @@ static int cap_booke_sregs;
>  static int cap_ppc_smt;
>  static int cap_ppc_rma;
>  static int cap_spapr_tce;
> +static int cap_spapr_tce_64;
>  static int cap_spapr_multitce;
>  static int cap_spapr_vfio;
>  static int cap_hior;
> @@ -123,6 +124,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>      cap_ppc_smt = kvm_check_extension(s, KVM_CAP_PPC_SMT);
>      cap_ppc_rma = kvm_check_extension(s, KVM_CAP_PPC_RMA);
>      cap_spapr_tce = kvm_check_extension(s, KVM_CAP_SPAPR_TCE);
> +    cap_spapr_tce_64 = kvm_check_extension(s, KVM_CAP_SPAPR_TCE_64);
>      cap_spapr_multitce = kvm_check_extension(s, KVM_CAP_SPAPR_MULTITCE);
>      cap_spapr_vfio = false;
>      cap_one_reg = kvm_check_extension(s, KVM_CAP_ONE_REG);
> @@ -2201,13 +2203,10 @@ bool kvmppc_spapr_use_multitce(void)
>      return cap_spapr_multitce;
>  }
>  
> -void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t window_size, int *pfd,
> -                              bool need_vfio)
> +void *kvmppc_create_spapr_tce(uint32_t liobn, uint32_t page_shift,
> +                              uint64_t bus_offset, uint32_t nb_table,
> +                              int *pfd, bool need_vfio)
>  {
> -    struct kvm_create_spapr_tce args = {
> -        .liobn = liobn,
> -        .window_size = window_size,
> -    };
>      long len;
>      int fd;
>      void *table;
> @@ -2220,14 +2219,41 @@ void *kvmppc_create_spapr_tce(uint32_t liobn, 
> uint32_t window_size, int *pfd,
>          return NULL;
>      }
>  
> -    fd = kvm_vm_ioctl(kvm_state, KVM_CREATE_SPAPR_TCE, &args);
> -    if (fd < 0) {
> -        fprintf(stderr, "KVM: Failed to create TCE table for liobn 0x%x\n",
> -                liobn);
> +    if (cap_spapr_tce_64) {
> +        struct kvm_create_spapr_tce_64 args = {
> +            .liobn = liobn,
> +            .page_shift = page_shift,
> +            .offset = bus_offset >> page_shift,
> +            .size = nb_table,
> +            .flags = 0
> +        };
> +        fd = kvm_vm_ioctl(kvm_state, KVM_CREATE_SPAPR_TCE_64, &args);
> +        if (fd < 0) {
> +            fprintf(stderr,
> +                    "KVM: Failed to create TCE64 table for liobn 0x%x\n",
> +                    liobn);
> +            return NULL;
> +        }
> +    } else if (cap_spapr_tce) {
> +        uint64_t window_size = (uint64_t) nb_table << page_shift;
> +        struct kvm_create_spapr_tce args = {
> +            .liobn = liobn,
> +            .window_size = window_size,
> +        };
> +        if ((window_size != args.window_size) || bus_offset) {
> +            return NULL;
> +        }
> +        fd = kvm_vm_ioctl(kvm_state, KVM_CREATE_SPAPR_TCE, &args);
> +        if (fd < 0) {
> +            fprintf(stderr, "KVM: Failed to create TCE table for liobn 
> 0x%x\n",
> +                    liobn);
> +            return NULL;
> +        }
> +    } else {
>          return NULL;
>      }
>  
> -    len = (window_size / SPAPR_TCE_PAGE_SIZE) * sizeof(uint64_t);
> +    len = nb_table * sizeof(uint64_t);
>      /* FIXME: round this up to page size */
>  
>      table = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 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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