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

[Alexey Kardashevskiy]

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 <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.


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.


> 
>> +        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);
> 


-- 
Alexey

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