Re: [Qemu-devel] [PATCH RESEND v1 1/2] i386: Add Intel Processor Trace feature support

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Jan 09, 2018 at 04:36:36AM +0800, Luwei Kang wrote:
> From: Chao Peng <chao.p.peng@linux.intel.com>
> 
> Expose Intel Processor Trace feature to guest.
> 
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> Signed-off-by: Luwei Kang <luwei.kang@intel.com>
> ---
>  target/i386/cpu.c | 19 ++++++++++++++++++-
>  target/i386/cpu.h |  1 +
>  target/i386/kvm.c | 23 +++++++++++++++++++++++
>  3 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 3818d72..57f8370 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -427,7 +427,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
>              NULL, NULL, "mpx", NULL,
>              "avx512f", "avx512dq", "rdseed", "adx",
>              "smap", "avx512ifma", "pcommit", "clflushopt",
> -            "clwb", NULL, "avx512pf", "avx512er",
> +            "clwb", "intel-pt", "avx512pf", "avx512er",
>              "avx512cd", "sha-ni", "avx512bw", "avx512vl",
>          },
>          .cpuid_eax = 7,
> @@ -3006,6 +3006,23 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
>          }
>          break;
>      }
> +    case 0x14: {
> +        if ((env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) &&
> +             kvm_enabled()) {
> +            KVMState *s = cs->kvm_state;
> +
> +            *eax = kvm_arch_get_supported_cpuid(s, 0x14, count, R_EAX);
> +            *ebx = kvm_arch_get_supported_cpuid(s, 0x14, count, R_EBX);
> +            *ecx = kvm_arch_get_supported_cpuid(s, 0x14, count, R_ECX);
> +            *edx = kvm_arch_get_supported_cpuid(s, 0x14, count, R_EDX);

If you are forwarding host info directly to the guest, the
feature is not migration-safe.  The new feature needs to be added
to feature_word_info[FEAT_7_0_EBX].unmigratable_flags.


> +        } else {
> +            *eax = 0;
> +            *ebx = 0;
> +            *ecx = 0;
> +            *edx = 0;
> +        }
> +        break;
> +    }
>      case 0x40000000:
>          /*
>           * CPUID code in kvm_arch_init_vcpu() ignores stuff
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 62c4742..58a4b6c 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -642,6 +642,7 @@ typedef uint32_t FeatureWordArray[FEATURE_WORDS];
>  #define CPUID_7_0_EBX_PCOMMIT  (1U << 22) /* Persistent Commit */
>  #define CPUID_7_0_EBX_CLFLUSHOPT (1U << 23) /* Flush a Cache Line Optimized */
>  #define CPUID_7_0_EBX_CLWB     (1U << 24) /* Cache Line Write Back */
> +#define CPUID_7_0_EBX_INTEL_PT (1U << 25) /* Intel Processor Trace */
>  #define CPUID_7_0_EBX_AVX512PF (1U << 26) /* AVX-512 Prefetch */
>  #define CPUID_7_0_EBX_AVX512ER (1U << 27) /* AVX-512 Exponential and Reciprocal */
>  #define CPUID_7_0_EBX_AVX512CD (1U << 28) /* AVX-512 Conflict Detection */
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 6f69e2f..e13ab58 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -863,6 +863,29 @@ int kvm_arch_init_vcpu(CPUState *cs)
>                  c = &cpuid_data.entries[cpuid_i++];
>              }
>              break;
> +        case 0x14: {
> +            uint32_t times;
> +
> +            c->function = i;
> +            c->index = 0;
> +            c->flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> +            cpu_x86_cpuid(env, i, 0, &c->eax, &c->ebx, &c->ecx, &c->edx);
> +            times = c->eax;
> +
> +            for (j = 1; j <= times; ++j) {
> +                if (cpuid_i == KVM_MAX_CPUID_ENTRIES) {
> +                    fprintf(stderr, "cpuid_data is full, no space for "
> +                                "cpuid(eax:0x14,ecx:0x%x)\n", j);
> +                    abort();
> +                }
> +                c = &cpuid_data.entries[cpuid_i++];
> +                c->function = i;
> +                c->index = j;
> +                c->flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
> +                cpu_x86_cpuid(env, i, j, &c->eax, &c->ebx, &c->ecx, &c->edx);
> +            }
> +            break;
> +        }
>          default:
>              c->function = i;
>              c->flags = 0;
> -- 
> 1.8.3.1
> 

-- 
Eduardo