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    SubjectRe: [PATCH] x86: properly handle KVM emulation of hyperv
    Il 19/07/2013 12:25, Jason Wang ha scritto:
    > Recent kvm has some basic support of hyperv, this will cause the guest to
    > identify itself running on top of hyperv instead of kvm which will disable kvm
    > pv functionality. Solve this by check kvm para platform first and also check
    > KVM_CPUID_SIGNATURE_NEXT which were set when kvm emulate hyperv.
    >
    > Cc: Gleb Natapov <gleb@redhat.com>
    > Cc: Paolo Bonzini <pbonzini@redhat.com>
    > Cc: Vadim Rozenfeld <vrozenfe@redhat.com>
    > Cc: K. Y. Srinivasan <kys@microsoft.com>
    > Cc: Thomas Gleixner <tglx@linutronix.de>
    > Cc: Ingo Molnar <mingo@redhat.com>
    > Cc: "H. Peter Anvin" <hpa@zytor.com>
    > Signed-off-by: Jason Wang <jasowang@redhat.com>
    > ---
    > arch/x86/include/asm/kvm_para.h | 25 +++++++++++++++++--------
    > arch/x86/include/uapi/asm/kvm_para.h | 1 +
    > arch/x86/kernel/cpu/hypervisor.c | 2 +-
    > 3 files changed, 19 insertions(+), 9 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
    > index 695399f..aa8f3a7 100644
    > --- a/arch/x86/include/asm/kvm_para.h
    > +++ b/arch/x86/include/asm/kvm_para.h
    > @@ -85,22 +85,31 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1,
    > return ret;
    > }
    >
    > -static inline bool kvm_para_available(void)
    > +static inline bool kvm_para_available_function(unsigned int function)
    > {
    > unsigned int eax, ebx, ecx, edx;
    > char signature[13];
    >
    > + cpuid(function, &eax, &ebx, &ecx, &edx);
    > + memcpy(signature + 0, &ebx, 4);
    > + memcpy(signature + 4, &ecx, 4);
    > + memcpy(signature + 8, &edx, 4);
    > + signature[12] = 0;
    > +
    > + if (strcmp(signature, "KVMKVMKVM") == 0)
    > + return true;
    > +
    > + return false;
    > +}
    > +
    > +static inline bool kvm_para_available(void)
    > +{
    > if (boot_cpu_data.cpuid_level < 0)
    > return false; /* So we don't blow up on old processors */
    >
    > if (cpu_has_hypervisor) {
    > - cpuid(KVM_CPUID_SIGNATURE, &eax, &ebx, &ecx, &edx);
    > - memcpy(signature + 0, &ebx, 4);
    > - memcpy(signature + 4, &ecx, 4);
    > - memcpy(signature + 8, &edx, 4);
    > - signature[12] = 0;
    > -
    > - if (strcmp(signature, "KVMKVMKVM") == 0)
    > + if (kvm_para_available_function(KVM_CPUID_SIGNATURE) ||
    > + kvm_para_available_function(KVM_CPUID_SIGNATURE_NEXT))
    > return true;
    > }

    Nice catch. Just one small thing, you should loop until 0x40010000, as
    done in arch/x86/include/asm/xen/hypervisor.h, in case one day a third
    hypervisor implements three extensions (Hyper-V, KVM and its own set).

    Paolo



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