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    SubjectRe: [PATCH 4/6] export new cpuid KVM_CAP
    On Mon, Apr 26, 2010 at 01:46:26PM -0400, Glauber Costa wrote:
    > Since we're changing the msrs kvmclock uses, we have to communicate
    > that to the guest, through cpuid. We can add a new KVM_CAP to the
    > hypervisor, and then patch userspace to recognize it.
    >
    > And if we ever add a new cpuid bit in the future, we have to do that again,
    > which create some complexity and delay in feature adoption.
    >
    > Instead, what I'm proposing in this patch is a new capability, called
    > KVM_CAP_X86_CPUID_FEATURE_LIST, that returns the current feature list
    > currently supported by the hypervisor. If we ever want to add or remove
    > some feature, we only need to tweak into the HV, leaving userspace untouched.
    >
    > Signed-off-by: Glauber Costa <glommer@redhat.com>
    > ---
    > arch/x86/include/asm/kvm_para.h | 4 ++++
    > arch/x86/kvm/x86.c | 6 ++++++
    > include/linux/kvm.h | 1 +
    > 3 files changed, 11 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
    > index 9734808..f019f8c 100644
    > --- a/arch/x86/include/asm/kvm_para.h
    > +++ b/arch/x86/include/asm/kvm_para.h
    > @@ -16,6 +16,10 @@
    > #define KVM_FEATURE_CLOCKSOURCE 0
    > #define KVM_FEATURE_NOP_IO_DELAY 1
    > #define KVM_FEATURE_MMU_OP 2
    > +/* This indicates that the new set of kvmclock msrs
    > + * are available. The use of 0x11 and 0x12 is deprecated
    > + */
    > +#define KVM_FEATURE_CLOCKSOURCE2 3
    >
    > #define MSR_KVM_WALL_CLOCK 0x11
    > #define MSR_KVM_SYSTEM_TIME 0x12
    > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > index a2ead7f..04f04aa 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -1545,6 +1545,12 @@ int kvm_dev_ioctl_check_extension(long ext)
    > case KVM_CAP_MCE:
    > r = KVM_MAX_MCE_BANKS;
    > break;
    > + case KVM_CAP_X86_CPUID_FEATURE_LIST:
    > + r = (1 << KVM_FEATURE_CLOCKSOURCE) |
    > + (1 << KVM_FEATURE_NOP_IO_DELAY) |
    > + (1 << KVM_FEATURE_MMU_OP) |

    Remove this flag, it has been deprecated.

    > + (1 << KVM_FEATURE_CLOCKSOURCE2);
    > + break;
    > default:

    Also missing qemu-kvm/qemu patches.



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