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

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Jan 09, 2017 at 01:38:26PM +1100, Alexey Kardashevskiy wrote:
> On 03/01/17 13:26, David Gibson wrote:
> > 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 <aik@ozlabs.ru>
> >> ---
> >>  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.
> 
> 
> No, kvmppc_create_spapr_tce() would return NULL and right after that there
> is a "if (!table)" (it can be seen at the end of this chunk) to handle the
> failure.

Oh, yes, sorry.  For some reason I thought there was a return in that
if block.

> > 
> >> +        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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