Re: [PATCH 3/3] spapr: Set ibm, pa-features HTM from KVM_CAP_PPC_HTM

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

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On Tue, Jul 05, 2016 at 03:19:24PM +1000, Sam Bobroff wrote:
> Advertise HTM support in ibm, pa-features if KVM indicates support when
> queried via a new capability (KVM_CAP_PPC_HTM).
> 
> If KVM returns false for the capability (which may indicate that the
> host kernel doesn't support the capability itself) attempt to
> determine availability using a fallback method based on KVM being
> KVM-HV and HTM being available to the QEMU process.
> 
> Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
> ---
>  hw/ppc/spapr.c       |  3 ++-
>  target-ppc/kvm.c     | 27 +++++++++++++++++++++++++++
>  target-ppc/kvm_ppc.h |  6 ++++++
>  3 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 704aae7..e229532 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -606,6 +606,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
>      uint32_t tbfreq = kvm_enabled() ? kvmppc_get_tbfreq()
>          : SPAPR_TIMEBASE_FREQ;
>      uint32_t cpufreq = kvm_enabled() ? kvmppc_get_clockfreq() : 1000000000;
> +    uint8_t htm = (kvm_enabled() && kvmppc_get_htm_support(env)) ? 0x80 : 0x00;

You can simplify this if you make kvmppc_get_htm_support() return
false when !kvm_enabled().

>      uint32_t page_sizes_prop[64];
>      size_t page_sizes_prop_size;
>      uint32_t vcpus_per_socket = smp_threads * smp_cores;
> @@ -635,7 +636,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
>          0xf6, 0x1f, 0xc7, 0xc0, 0x80, 0xf0,
>          0x80, 0x00, 0x00, 0x00, 0x00, 0x00,
>          0x00, 0x00, 0x00, 0x00, 0x80, 0x00,
> -        0x80, 0x00, 0x80, 0x00, 0x00, 0x00 };
> +        0x80, 0x00, 0x80, 0x00, 0x00 | htm, 0x00 };

I think it would be easier to read if the initializer is kept constant
and you fold in the htm bit in the actual code.

>      uint8_t *pa_features;
>      size_t pa_size;
>  
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index 884d564..f94ce3b 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -20,6 +20,7 @@
>  #include <sys/vfs.h>
>  
>  #include <linux/kvm.h>
> +#include "elf.h"
>  
>  #include "qemu-common.h"
>  #include "qemu/error-report.h"
> @@ -1976,6 +1977,32 @@ uint32_t kvmppc_get_dfp(void)
>      return kvmppc_read_int_cpu_dt("ibm,dfp");
>  }
>  
> +bool kvmppc_get_htm_support(CPUPPCState *env)
> +{
> +    PowerPCCPU *cpu = ppc_env_get_cpu(env);
> +    CPUState *cs = CPU(cpu);
> +
> +
> +    if (kvm_vm_check_extension(cs->kvm_state, KVM_CAP_PPC_HTM)) {
> +        return true;
> +    }
> +    /*
> +     * Fallback test for host kernels that don't yet support KVM_CAP_PPC_HTM.
> +     * This will be unnecessary when KVM_API_VERSION is incremented (to 13 or
> +     * above) because that will remove the ambiguity between the host kernel
> +     * lacking support for KVM_CAP_PPC_HTM and it having support but reporting
> +     * HTM as unavailable (both of which return 0, above).
> +     */
> +    if (kvm_vm_check_extension(cs->kvm_state, KVM_CAP_PPC_GET_PVINFO)) {
> +        /* Assume this means PR KVM, so no TM. */
> +        return false;
> +    } else {
> +        /* Assume this means HV KVM, propagate whatever host userspace sees. */
> +        unsigned long hwcap2 = qemu_getauxval(AT_HWCAP2);
> +        return !!(hwcap2 & PPC_FEATURE2_HAS_HTM);
> +    }
> +}
> +
>  static int kvmppc_get_pvinfo(CPUPPCState *env, struct kvm_ppc_pvinfo *pvinfo)
>   {
>       PowerPCCPU *cpu = ppc_env_get_cpu(env);
> diff --git a/target-ppc/kvm_ppc.h b/target-ppc/kvm_ppc.h
> index 20bfb59..b01c717 100644
> --- a/target-ppc/kvm_ppc.h
> +++ b/target-ppc/kvm_ppc.h
> @@ -17,6 +17,7 @@ uint32_t kvmppc_get_tbfreq(void);
>  uint64_t kvmppc_get_clockfreq(void);
>  uint32_t kvmppc_get_vmx(void);
>  uint32_t kvmppc_get_dfp(void);
> +bool kvmppc_get_htm_support(CPUPPCState *env);
>  bool kvmppc_get_host_model(char **buf);
>  bool kvmppc_get_host_serial(char **buf);
>  int kvmppc_get_hasidle(CPUPPCState *env);
> @@ -90,6 +91,11 @@ static inline uint32_t kvmppc_get_dfp(void)
>      return 0;
>  }
>  
> +static inline bool kvmppc_get_htm_support(KVMState *kvm_state)
> +{
> +    return false;
> +}
> +
>  static inline int kvmppc_get_hasidle(CPUPPCState *env)
>  {
>      return 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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